## Problem
Hard to tell
1. How many clients are connected to proxy
2. How many requests clients are making
3. How many connections are made to a database
1 and 2 are different because of the properties of HTTP.
We have 2 already tracked through `proxy_accepted_connections_total` and
`proxy_closed_connections_total`, but nothing for 1 and 3
## Summary of changes
Adds 2 new counter gauges.
*
`proxy_opened_client_connections_total`,`proxy_closed_client_connections_total`
- how many client connections are open to proxy
*
`proxy_opened_db_connections_total`,`proxy_closed_db_connections_total`
- how many active connections are made through to a database.
For TCP and Websockets, we expect all 3 of these quantities to be
roughly the same, barring users connecting but with invalid details.
For HTTP:
* client_connections/connections can differ because the client
connections can be reused.
* connections/db_connections can differ because of connection pooling.
## Problem
close https://github.com/neondatabase/neon/issues/4702
## Summary of changes
This PR adds a new metrics for wake up errors and breaks it down by most
common reasons (mostly follows the `could_retry` implementation).
## Problem
If a caller detaches a tenant and then attaches it again, pending
deletions from the old attachment might not have happened yet. This is
not a correctness problem, but it causes:
- Risk of leaking some objects in S3
- Some warnings from the deletion queue when pending LSN updates and
pending deletions don't pass validation.
## Summary of changes
- Deletion queue now uses UnboundedChannel so that the push interfaces
don't have to be async.
- This was pulled out of https://github.com/neondatabase/neon/pull/5397,
where it is also useful to be able to drive the queue from non-async
contexts.
- Why is it okay for this to be unbounded? The only way the
unbounded-ness of the channel can become a problem is if writing out
deletion lists can't keep up, but if the system were that overloaded
then the code generating deletions (GC, compaction) would also be
impacted.
- DeletionQueueClient gets a new `flush_advisory` function, which is
like flush_execute, but doesn't wait for completion: this is appropriate
for use in contexts where we would like to encourage the deletion queue
to flush, but don't need to block on it.
- This function is also expected to be useful in next steps for seamless
migration, where the option to flush to S3 while transitioning into
AttachedStale will also include flushing deletion queue, but we wouldn't
want to block on that flush.
- The tenant_detach code in mgr.rs invokes flush_advisory after stopping
the `Tenant` object.
---------
Co-authored-by: Arpad Müller <arpad-m@users.noreply.github.com>
## Problem
We don't want to retry customer quota exhaustion errors.
## Summary of changes
Make sure both types of quota exhaustion errors are not retried
## Problem
See https://neondb.slack.com/archives/C05U648A9NJ
In case of failure of flush in prefetch,
prefetch state is reseted. We need to retry register buffer attempt,
otherwise we will get assertion failure.
## Checklist before requesting a review
- [ ] I have performed a self-review of my code.
- [ ] If it is a core feature, I have added thorough tests.
- [ ] Do we need to implement analytics? if so did you add the relevant
metrics to the dashboard?
- [ ] If this PR requires public announcement, mark it with
/release-notes label and add several sentences in this section.
## Checklist before merging
- [ ] Do not forget to reformat commit message to not include the above
checklist
---------
Co-authored-by: Konstantin Knizhnik <knizhnik@neon.tech>
## Problem
Seen in CI for https://github.com/neondatabase/neon/pull/5453 -- the
time gap between validation completing and the header getting written is
long enough to fail the test, where it was doing a cheeky 1 second
sleep.
## Summary of changes
- Replace 1 second sleep with a wait_until to see the header file get
written
- Use enums as test params to make the results more readable (instead of
True-False parameters)
- Fix the temp suffix used for deletion queue headers: this worked fine,
but resulted in `..tmp` extension.
## Problem
Writes to the postgres client socket from the page server were not
wrapped in cancellation handling, so a stuck client connection could
prevent tenant shutdowwn.
## Summary of changes
All the places we call flush() to write to the socket, we should be
respecting the cancellation token for the task.
In this PR, I explicitly pass around a CancellationToken rather than
doing inline `task_mgr::shutdown_token` calls, to avoid coupling it to
the global task_mgr state and make it easier to refactor later.
I have some follow-on commits that add a Shutdown variant to QueryError
and use it more extensively, but that's pure refactor so will keep
separate from this bug fix PR.
Closes: https://github.com/neondatabase/neon/issues/5341
Part of #5172. First commits show that we used to allow starting up a
compute or creating a branch off a not yet uploaded timeline. This PR
moves activation of a timeline to happen **after** initial layer file(s)
(if any) and `index_part.json` have been uploaded. Simply moving
activation to be *after* downloads have finished works because we now
spawn a task per http request handler.
Current behaviour of uploading on the timelines on next startup is kept,
to be removed later as part of #5172.
Adds:
- `NeonCli.map_branch` and corresponding `neon_local` implementation:
allow creating computes for timelines managed via pageserver http
client/api
- possibly duplicate tests (I did not want to search for, will cleanup
in a follow-up if these duplicated)
Changes:
- make `wait_until_tenant_state` return immediatedly on `Broken` and not
wait more
## Problem
Fix neon_local pageserver status command
#5430
## Summary of changes
Fix clap config for pageserver status subcommand
## Checklist before requesting a review
- [x] I have performed a self-review of my code.
- [ ] If it is a core feature, I have added thorough tests.
- [ ] Do we need to implement analytics? if so did you add the relevant
metrics to the dashboard?
- [ ] If this PR requires public announcement, mark it with
/release-notes label and add several sentences in this section.
Signed-off-by: Rahul Modpur <rmodpur2@gmail.com>
## Problem
Pageservers with `control_plane_api` configured require a control plane
to start up: in an incident this might be a problem.
## Summary of changes
Note to reviewers: most of the code churn in mgr.rs is the refactor
commit that enables the later emergency mode commit: you may want to
review commits separately.
- Add `control_plane_emergency_mode` configuration property
- Refactor init_tenant_mgr to separate loading configurations from the
main loop where we construct Tenant, so that the generations fetch can
peek at the configs in emergency mode.
- During startup, in emergency mode, attach any tenants that were
attached on their last run, using the same generation number.
Closes: #5381
Closes: https://github.com/neondatabase/neon/issues/5492
## Problem
Spun off from https://github.com/neondatabase/neon/pull/5449
Timeline deletion does the following:
1. Delete layers referenced in the index
2. Delete everything else in the timeline prefix, except the index
3. Delete the index.
When generations were added, the filter in step 2 got outdated, such
that the index objects were deleted along with everything else at step
2. That didn't really break anything, but it makes an automated test
unhappy and is a violation of the original intent of the code, which
presumably intends to upload an invariant that as long as any objects
for a timeline exist, the index exists.
(Eventually, this index-object-last complexity can go away: when we do
https://github.com/neondatabase/neon/issues/5080, there is no need to
keep the index_part around, as deletions can always be retried any time
any where.)
## Summary of changes
After object listing, split the listed objects into layers and index
objects. Delete the layers first, then the index objects.
Doesn't do an upgrade of rustc to 1.73.0 as we want to wait for the
cargo response of the curl CVE before updating. In preparation for an
update, we address the clippy lints that are newly firing in 1.73.0.
Problem
=======
Prior to this PR, when we had a cache miss, we'd get back a write guard,
fill it, the drop it and retry the read from cache.
If there's severe contention for the cache, it could happen that the
just-filled data gets evicted before our retry, resulting in lost work
and no forward progress.
Solution
========
This PR leverages the now-available `tokio::sync::RwLockWriteGuard`'s
`downgrade()` functionality to turn the filled slot write guard into a
read guard.
We don't drop the guard at any point, so, forward progress is ensured.
Refs
====
Stacked atop https://github.com/neondatabase/neon/pull/5480
part of https://github.com/neondatabase/neon/issues/4743
specifically part of https://github.com/neondatabase/neon/issues/5479
If there are any layermap or layer file related problems, having a
reproducable `get_page@lsn` easily usable for fast debugging iteration
is helpful.
Split off from #4938.
Later evolved to add http apis for:
- `get_page@lsn` at
`/v1/tenant/:tenant_id/timeline/:timeline_id/get?key=<hex>&lsn=<lsn
string>`
- collecting the keyspace at
`/v1/tenant/:tenant_id/timeline/:timeline_id/keyspace?[at_lsn=<lsn
string>]`
- defaults to `last_record_lsn`
collecting the keyspace seems to yield some ranges for which there is no
key.
503 Resource Unavailable appears as error in logs, but is not really an
error which should ever fail a test on, or even log an error in prod,
[evidence].
Changes:
- log 503 as `info!` level
- use `Cow<'static, str>` instead of `String`
- add an additional `wait_until_tenant_active` in
`test_actually_duplicate_l1`
We ought to have in tests "wait for tenants to complete loading" but
this is easier to implement for now.
[evidence]:
https://neon-github-public-dev.s3.amazonaws.com/reports/pr-5485/6423110295/index.html#/testresult/182de66203864fc0
## Problem
`test_tenant_delete_is_resumed_on_attach` is flaky
## Summary of changes
- Allow race in `test_tenant_delete_is_resumed_on_attach`
- Cleanup `allowed_errors` in the file a bit
Clean subprocess output so that:
- one line of output is just one line without a linebreak
- like shells handle `echo subshell says: $(echo foo)`
- multiple lines are indented like other pytest output
- error output is dedented and then indented to be like other pytest
output
Minor readability changes remove friction.
This patch extracts all postgres-dependent functions in a separate
`walproposer_api` functions struct. It helps to compile walproposer as
static library without compiling all other postgres server code. This is
useful to allow calling walproposer C code from Rust, or linking this
library with anything else.
All global variables containing walproposer state were extracted to a
separate `WalProposer` struct. This makes it possible to run several
walproposers in the same process, in separate threads.
There were no logic changes and PR mostly consists of shuffling
functions between several files. We have a good test coverage for
walproposer code and I've seen no issues with tests while I was
refactoring it, so I don't expect any issues after merge.
ref https://github.com/neondatabase/neon/issues/547
---------
Co-authored-by: Arseny Sher <sher-ars@yandex.ru>
## Problem
This test was unstable when run in parallel with lots of others: if the
pageserver stayed up long enough for some of the deletions to get
validated, they won't be discarded on restart the way the test expects
when keep_attachment=True. This was a test bug, not a pageserver bug.
## Summary of changes
- Add failpoints to control plane api client
- Use failpoint to pause validation in the test to cover the case where
it had been flaky
- Add a metric for the number of deleted keys validated
- Add a permutation to the test to additionally exercise the case where
we _do_ validate lists before restart: this is a coverage enhancement
that seemed sensible when realizing that the test was relying on nothing
being validated before restart.
- the test will now always enter the restart with nothing or everything
validated.
## Problem
These changes are part of building seamless tenant migration, as
described in the RFC:
- https://github.com/neondatabase/neon/pull/5029
## Summary of changes
- A new configuration type `LocationConf` supersedes `TenantConfOpt` for
storing a tenant's configuration in the pageserver repo dir. It contains
`TenantConfOpt`, as well as a new `mode` attribute that describes what
kind of location this is (secondary, attached, attachment mode etc). It
is written to a file called `config-v1` instead of `config` -- this
prepares us for neatly making any other profound changes to the format
of the file in future. Forward compat for existing pageserver code is
achieved by writing out both old and new style files. Backward compat is
achieved by checking for the old-style file if the new one isn't found.
- The `TenantMap` type changes, to hold `TenantSlot` instead of just
`Tenant`. The `Tenant` type continues to be used for attached tenants
only. Tenants in other states (such as secondaries) are represented by a
different variant of `TenantSlot`.
- Where `Tenant` & `Timeline` used to hold an Arc<Mutex<TenantConfOpt>>,
they now hold a reference to a AttachedTenantConf, which includes the
extra information from LocationConf. This enables them to know the
current attachment mode.
- The attachment mode is used as an advisory input to decide whether to
do compaction and GC (AttachedStale is meant to avoid doing uploads,
AttachedMulti is meant to avoid doing deletions).
- A new HTTP API is added at `PUT /tenants/<tenant_id>/location_config`
to drive new location configuration. This provides a superset of the
functionality of attach/detach/load/ignore:
- Attaching a tenant is just configuring it in an attached state
- Detaching a tenant is configuring it to a detached state
- Loading a tenant is just the same as attaching it
- Ignoring a tenant is the same as configuring it into Secondary with
warm=false (i.e. retain the files on disk but do nothing else).
Caveats:
- AttachedMulti tenants don't do compaction in this PR, but they do in
the follow on #5397
- Concurrent updates to the `location_config` API are not handled
elegantly in this PR, a better mechanism is added in the follow on
https://github.com/neondatabase/neon/pull/5367
- Secondary mode is just a placeholder in this PR: the code to upload
heatmaps and do downloads on secondary locations will be added in a
later PR (but that shouldn't change any external interfaces)
Closes: https://github.com/neondatabase/neon/issues/5379
---------
Co-authored-by: Christian Schwarz <christian@neon.tech>
## Problem
these JoinSets live for the duration of the process. they might have
many millions of connections spawned on them and they never get cleared.
Fixes#4672
## Summary of changes
Drain the connections as we go
## Problem
In #5383 this configuration was added, but it missed the parts of the
Builder class that let it actually be used.
## Summary of changes
Add `control_plane_api_token` hooks to PageserverConfigBuilder
If the cgroup integration was not enabled, this would cause compute_ctl
to leak memory.
Thankfully, we never use vm-monitor *without* the cgroup handling
enabled, so this wasn't actually impacting us, but... it still looked
suspicious, so figured it was worth changing.
We overwrite L1 layers if compaction gets interrupted. We did not have a
test showing that we do in fact do this.
The test might be a bit flaky due to timestamp usage, but separating for
smaller diff in as part of #5172.
Also removes an unrelated 200s pgbench from the test suite.
## Problem
- Because we compress artifacts file by file, we don't need to put them
into `tar` containers (ie instead of `tar.gz` we can use just `gz`).
- Pythons gz single-threaded and pretty slow.
A benchmark has shown ~20 times speedup (19.876176291 vs
0.8748335830000009) on my laptop (for a pageserver.log size is 1.3M)
## Summary of changes
- Replace tarfile with zstandart
- Update allure to 2.24.0
Fixes#4689 by replacing all of `std::Path` , `std::PathBuf` with
`camino::Utf8Path`, `camino::Utf8PathBuf` in
- pageserver
- safekeeper
- control_plane
- libs/remote_storage
Co-authored-by: Joonas Koivunen <joonas@neon.tech>
## Problem
1MB request body is apparently too small for some clients
## Summary of changes
Update to 10 MB request body. Also revert the removal of response limits
while we don't have streaming support.
We currently lose the actual reason the first walredo attempt failed.
Together with implicit retry making it difficult to eyeball what is
happening.
PR version keeps the logging the same error message twice, which is what
we've been doing all along. However correlating the retrying case and
the finally returned error is difficult, because the actual error
message was left out before this PR.
Lastly, log the final error we present to postgres *in the same span*,
not outside it. Additionally, suppress the stacktrace as the comment
suggested.
We have rare walredo failures with pg16.
Let's introduce recording of failing walredo input in `#[cfg(feature =
"testing")]`. There is additional logging (the value reconstruction path
logging usually shown with not found keys), keeping it for
`#[cfg(features = "testing")]`.
Cc: #5404.
## Problem
Duplication of error in log
Fixes#5366
## Summary of changes
Removed `{0}` from error description above each enum due to presence of
`#[source]` to avoid duplication
Signed-off-by: Rahul Modpur <rmodpur2@gmail.com>
## Problem
Folks have re-taged releases for `pg_jsonschema` and `pg_graphql` (to
increase timeouts on their CI), for us, these are a noop changes,
but unfortunately, this will cause our builds to fail due to checksums
mismatch (this might not strike right away because of the build cache).
- 8ba7c7be9d
- aa7509370a
## Summary of changes
- `pg_jsonschema` update checksum
- `pg_graphql` update checksum
## Problem
Folks have re-taged releases for `pg_jsonschema` and `pg_graphql` (to
increase timeouts on their CI), for us, these are a noop changes,
but unfortunately, this will cause our builds to fail due to checksums
mismatch (this might not strike right away because of the build cache).
- 8ba7c7be9d
- aa7509370a
## Summary of changes
- `pg_jsonschema` update checksum
- `pg_graphql` update checksum
## Problem
The 500 status code should only be used for bugs or unrecoverable
failures: situations we did not expect. Currently, the pageserver is
misusing this response code for some situations that are totally normal,
like requests targeting tenants that are in the process of activating.
The 503 response is a convenient catch-all for "I can't right now, but I
will be able to".
## Summary of changes
- Change some transient availability error conditions to return 503
instead of 500
- Update the HTTP client configuration in integration tests to retry on
503
After these changes, things like creating a tenant and then trying to
create a timeline within it will no longer require carefully checking
its status first, or retrying on 500s. Instead, a client which is
properly configured to retry on 503 can quietly handle such situations.
- Update `pg_jsonschema` to 0.2.0 with Postgres 16 support
- Update `pg_grapgql` to 1.4.0 with Postgres 16 support
- Remove `pgx` (old name of `pgrx`) layer from Dockerfile
- Update `pgx-ulid` from 0.1.0 to 0.1.3, and add it to Postgres 16
- Add `pg_tiktoken` to Postgres 16 image
Closes#5374
---------
Co-authored-by: Alexander Bayandin <alexander@neon.tech>
## Problem
If the control plane happened to respond to a DROP DATABASE request with
a non-200 response, we'd abort the DROP DATABASE transaction in the
usual spot. However, Postgres for some reason actually performs the drop
inside of `standard_ProcessUtility`. As such, the database was left in a
weird state after aborting the transaction. We had test coverage of a
failed CREATE DATABASE but not a failed DROP DATABASE.
## Summary of changes
Since DROP DATABASE can't be inside of a transaction block, we can just
forward the DDL changes to the control plane inside of
`ProcessUtility_hook`, and if we respond with 500 bail out of
`ProcessUtility` before we perform the drop. This change also adds a
test, which reproduced the invalid database issue before the fix was
applied.
It is wasteful to cycle through the page cache slots trying to find a
victim slot if all the slots are currently un-evictable because a read /
write guard is alive.
We suspect this wasteful cycling to be the root cause for an
"indigestion" we observed in staging (#5291).
The hypothesis is that we `.await` after we get ahold of a read / write
guard, and that tokio actually deschedules us in favor of another
future.
If that other future then needs a page slot, it can't get ours because
we're holding the guard.
Repeat this, and eventually, the other future(s) will find themselves
doing `find_victim` until they hit `exceeded evict iter limit`.
The `find_victim` is wasteful and CPU-starves the futures that are
already holding the read/write guard. A `yield` inside `find_victim`
could mitigate the starvation, but wouldn't fix the wasting of CPU
cycles.
So instead, this PR queues waiters behind a tokio semaphore that counts
evictable slots.
The downside is that this stops the clock page replacement if we have 0
evictable slots.
Also, as explained by the big block comment in `find_victims`, the
semaphore doesn't fully prevent starvation because because we can't make
tokio prioritize those tasks executing `find_victim` that have been
trying the longest.
Implementation
===============
We need to acquire the semaphore permit before locking the slot.
Otherwise, we could deadlock / discover that all permits are gone and
would have to relinquish the slot, having moved forward the Clock LRU
without making progress.
The downside is that, we never get full throughput for read-heavy
workloads, because, until the reader coalesces onto an existing permit,
it'll hold its own permit.
Addendum To Root-Cause Analysis In #5291
========================================
Since merging that PR, @arpad-m pointed out that we couldn't have
reached the `slot.write().await` with his patches because the
VirtualFile slots can't have all been write-locked, because we only hold
them locked while the IO is ongoing, and the IO is still done with
synchronous system calls in that patch set, so, we can have had at most
$number_of_executor_threads locked at any given time.
I count 3 tokio runtimes that do `Timeline::get`, each with 8 executor
threads in our deployment => $number_of_executor_threads = 3*8 = 24 .
But the virtual file cache has 100 slots.
We both agree that nothing changed about the core hypothesis, i.e.,
additional await points inside VirtualFile caused higher concurrency
resulting in exhaustion of page cache slots.
But we'll need to reproduce the issue and investigate further to truly
understand the root cause, or find out that & why we were indeed using
100 VirtualFile slots.
TODO: could it be compaction that needs to hold guards of many
VirtualFile's in its iterators?
## Problem
I've noticed that `hermit-abi`
0.3.1 [1] has been yanked from crates.io (looks like nothing too
bad [2]).
Also, we have 2 versions of `hermit-api` in dependencies (0.3.* and
0.2.*), update `num-cpus` to use the latest `hermit-api` 0.3.3.
- [1] https://crates.io/crates/hermit-abi/0.3.1
- [2] https://github.com/hermit-os/hermit-rs/issues/436
## Summary of changes
- `cargo update -p num-cpus`
- `cargo update -p hermit-abi`
- Unignore `RUSTSEC-2023-0052` in `deny.toml` (it has been fixed in
https://github.com/neondatabase/neon/pull/5069)
## Problem
Our SNI error dashboard features IP addresses but it's not immediately
clear who that is still (#5369)
## Summary of changes
Log some startup params with this error
## Problem
This test has been flaky for a long time.
As far as I can tell, the test was simply wrong to expect postgres
activity to result in deterministic sizes: making the match fuzzy is not
a hack, it's just matching the reality that postgres doesn't promise to
write exactly the same number of pages every time it runs a given query.
## Summary of changes
Equalities now tolerate up to 4 pages different. This is big enough to
tolerate the deltas we've seen in practice.
Closes: https://github.com/neondatabase/neon/issues/2962
When you log more than a few blocks, you need to reserve the space in
advance. We didn't do that, so we got errors. Now we do that, and
shouldn't get errors.
It is usually not intended to notify a random member of the compute team
for pageserver PRs.
Leaving the notification of the storage team in place, because this
serves a purpose when some external contributor opens a PR and isn't
sure who to ask.
## Problem
Because `neon_local` by default runs with no remote storage, it was not
running the deletion queue workers, and the attempt to call into
`recover()` was failing.
This is a bogus configuration that will go away when we make remote
storage mandatory.
## Summary of changes
Don't try and do deletion queue recovery when remote storage is
disabled.
The reason we don't just unset `control_plane_api` to avoid this is that
generations will soon become mandatory, irrespective of when we make
remote storage mandatory.
This effectively reverts #3832.
There's a couple issues we just discovered with the free space monitor,
and to my knowledge, the fact we're putting the file cache on a separate
filesystem (even when on disk) that's guaranteed to have more room than
the maximum size means that this free space monitor should have no
effect.
More details:
1. The control plane sets the maximum file cache size based on max CU
2. The control plane sets the size of the filesystem underlying the file
cache based on the maximum user selectable CU (or, if the endpoint is
larger, then that size), so that there's always enough room
3. If postmaster gets SIGKILL'd, then the free space monitor process
does not exit
4. If the free space monitor is acting on the cache file but not subject
to locking or up-to-date metadata from a newer postgres instance, then
this could lead to data corruption.
So, in practice I belive the risk of data corruption is *low* but not
nothing, and given the issues we hit because of (3), and given that this
the free space monitor shouldn't be necessary because of (1) and (2),
it's best to just remove it outright.
See also: neondatabase/autoscaling#534, #5405
## Problem
We need to count metrics always when a connection is open. Not only when
the transfer is 0.
We also need to count bytes usage for HTTP.
## Summary of changes
New structure for usage metrics. A `DashMap<Ids, Arc<Counters>>`.
If the arc has 1 owner (the map) then I can conclude that no connections
are open.
If the counters has "open_connections" non zero, then I can conclude a
new connection was opened in the last interval and should be reported
on.
Also, keep count of how many bytes processed for HTTP and report it
here.
Part of #5172. Builds upon #5243, #5298. Includes the test changes:
- no more RemoteStorageKind.NOOP
- no more testing of pageserver without remote storage
- benchmarks now use LOCAL_FS as well
Support for running without RemoteStorage is still kept but in practice,
there are no tests and should not be any tests.
Co-authored-by: Christian Schwarz <christian@neon.tech>
## Problem
Currently we don't have a way to migrate tenants from one pageserver to
another without a risk of gap in availability.
## Summary of changes
This follows on from https://github.com/neondatabase/neon/pull/4919
Migrating tenants between pageservers is essential to operating a
service
at scale, in several contexts:
1. Responding to a pageserver node failure by migrating tenants to other
pageservers
2. Balancing load and capacity across pageservers, for example when a
user expands their
database and they need to migrate to a pageserver with more capacity.
3. Restarting pageservers for upgrades and maintenance
Currently, a tenant may migrated by attaching to a new node,
re-configuring endpoints to use the new node, and then later detaching
from the old node. This is safe once [generation
numbers](025-generation-numbers.md) are implemented, but does meet
our seamless/fast/efficient goals:
Co-authored-by: Christian Schwarz <christian@neon.tech>
## Problem
Over the past couple days, we've had a couple VMs hit issues with
postgres getting hit by memory.high throttling, even after #5303 was
supposed to fix that. The tl;dr of those issues is that because
vm-monitor startup sets the file cache size first, before interacting
with the cgroup, cgroup throttling can mean we timeout connecting to the
file cache and never reset the cgroup, even if memory has been upscaled
since then.
See e.g.:
- https://neondb.slack.com/archives/C03F5SM1N02/p1695218132208249
- https://neondb.slack.com/archives/C03F5SM1N02/p1695314613696659
## Summary of changes
This PR adds an additional step into vm-monitor startup, where we first
set the cgroup's memory.high value to 'max', removing the capacity for
throttling. This preferable to just setting memory.high before the file
cache, because it's theoretically possible that the new value of
memory.high could still be less than the current memory usage, in which
case postgres could continue to be throttled without sufficient memory
events to relieve that.
Implementing this properly involved adding a method to our internal
cgroup interface, and it seemed like there was duplicated functionality
there, so this PR unifies that as well, making things a bit more
consistent.
## Problem
Control plane API calls in prod will need authentication.
## Summary of changes
`control_plane_api_token` config is loaded and set as HTTP
`Authorization` header.
Closes: https://github.com/neondatabase/neon/issues/5139
When you log more than a few blocks, you need to reserve the space in
advance. We didn't do that, so we got errors. Now we do that, and
shouldn't get errors.
Fixes#3978. `test_partial_evict_tenant` can fail multiple times so even
though we retry it as flaky, it will still haunt us.
Originally was going to just relax the comparison, then ended up
replacing warming up to use full table scans instead of `pgbench
--select-only`. This seems to help by producing the expected layer
accesses. There might be something off with how many layers pg16
produces compared to pg14 and pg15. Created #5392.
## Problem
Pageservers must not delete objects or advertise updates to
remote_consistent_lsn without checking that they hold the latest
generation for the tenant in question (see [the RFC](
https://github.com/neondatabase/neon/blob/main/docs/rfcs/025-generation-numbers.md))
In this PR:
- A new "deletion queue" subsystem is introduced, through which
deletions flow
- `RemoteTimelineClient` is modified to send deletions through the
deletion queue:
- For GC & compaction, deletions flow through the full generation
verifying process
- For timeline deletions, deletions take a fast path that bypasses
generation verification
- The `last_uploaded_consistent_lsn` value in `UploadQueue` is replaced
with a mechanism that maintains a "projected" lsn (equivalent to the
previous property), and a "visible" LSN (which is the one that we may
share with safekeepers).
- Until `control_plane_api` is set, all deletions skip generation
validation
- Tests are introduced for the new functionality in
`test_pageserver_generations.py`
Once this lands, if a pageserver is configured with the
`control_plane_api` configuration added in
https://github.com/neondatabase/neon/pull/5163, it becomes safe to
attach a tenant to multiple pageservers concurrently.
---------
Co-authored-by: Joonas Koivunen <joonas@neon.tech>
Co-authored-by: Christian Schwarz <christian@neon.tech>
Fixes#5072. See proof from
https://github.com/neondatabase/neon/issues/5072#issuecomment-1735580798.
Turns out multiple threads can get the same nanoseconds since epoch, so
switch to using millis (for finding the prefix later on) and randomness
via `thread_rng` (protect against adversial ci runners).
Also changes the "per test looking alike" prefix to more "general"
prefix.
The TaskKind dimension added in #5339 is insufficient to understand what
kind of data causes the cache hits.
Regarding performance considerations: I'm not too worried because we're
moving from 3 to 4 one-byte sized fields; likely the space now used by
the new field was padding before. Didn't check this, though, and it
doesn't matter, we need the data.
What I don't like about this PR is that we have an `Unknown` content
type, and I also don't like that there's no compile-time way to assert
that it's set to something != `Unknown` when calling the page cache.
But, this is what I could come up with before tomorrow’s release, and I
think it covers the hot paths.
## Problem
See https://neondb.slack.com/archives/C033RQ5SPDH/p1694595347598249
## Summary of changes
Update last written LSN after walloging all createdb stuff
## Checklist before requesting a review
- [ ] I have performed a self-review of my code.
- [ ] If it is a core feature, I have added thorough tests.
- [ ] Do we need to implement analytics? if so did you add the relevant
metrics to the dashboard?
- [ ] If this PR requires public announcement, mark it with
/release-notes label and add several sentences in this section.
## Checklist before merging
- [ ] Do not forget to reformat commit message to not include the above
checklist
---------
Co-authored-by: Konstantin Knizhnik <knizhnik@neon.tech>
Should have added them in the initial PR #5186.
Would have been nice to test the failure cases as well, but, without
mocking the FS, that's too hard / platform-dependent.
This PR adds a `task_kind` label to page cache access metrics.
These are to validate our hypothesis that the high hit page cache rate
we observe in prod is due to internal tasks, not getpage requests from
compute.
We believe the latter should near-always be a pageserver-page-cache
_miss_ because compute has it's own page cache, and hence there is no
locality of reference for its accesses to pageserver page cache.
Before this PR, we didn't have `RequestContext` propagation to any code
below the on-demand downloader.
The vast majority of changes in this PR is concerned with adding that
propagation.
## Problem
Compute start time has improved, but the timing of connection retries
from the proxy is rather slow, meaning we could be making clients wait
hundreds of milliseconds longer than necessary.
## Summary of changes
Previously, retry time in ms was `100 * 1.5**n`, and `n` starts at 1,
giving: 150, 225, 337, 506, 759, 1139, 1709, ...
This PR changes that to `25 * sqrt(2)**(n - 1)` instead, giving: 25, 35,
50, 71, 100, 141, 200, ...
## Problem
Do not allow new installation of deprecated `hnsw` extension.
The same approach as in https://github.com/neondatabase/neon/pull/5345
## Summary of changes
- Remove `trusted = true` from `hnsw.control`
- Remove `hnsw` related targets from Makefile
## Problem
Before releasing new version to production, we'd like to run a set of
required checks on the incoming release.
The simplest approach, which doesn't require many changes — dedicate one
staging region to `preprod` installation.
The proposed changes to the release flow are the following:
- When a release PR is merged into the release branch — trigger
deployment from the release branch to a dedicated staging-preprod region
(for now, it's going to be `eu-west-1` — Ireland)
Corresponding infrastructure PR:
https://github.com/neondatabase/aws/pull/585
## Summary of changes
- Trigger `deploy.dev` workflow with `-f deployPreprodRegion=true` for
release branch
## Problem
In 83e7e5dbbd dependencies were only
updated for Mac users. Without libicu, postgres 16 build fails.
## Summary of changes
Update dependencies on Ubuntu and fedora to include libicu.
## Problem
See https://neondb.slack.com/archives/C05L7D1JAUS/p1693775881474019
## Summary of changes
Do not perform local file cache resizing in processes having no PGPROC
## Checklist before requesting a review
- [ ] I have performed a self-review of my code.
- [ ] If it is a core feature, I have added thorough tests.
- [ ] Do we need to implement analytics? if so did you add the relevant
metrics to the dashboard?
- [ ] If this PR requires public announcement, mark it with
/release-notes label and add several sentences in this section.
## Checklist before merging
- [ ] Do not forget to reformat commit message to not include the above
checklist
---------
Co-authored-by: Konstantin Knizhnik <knizhnik@neon.tech>
Split off from #5297. Builds upon #5326. Handles original review
comments which I did not move to earlier split PRs. Completes test
support for verifying events by notifying of the last batch of events.
Adds cleaning up of tempfiles left because of an unlucky shutdown or
SIGKILL.
Finally closes#5175.
Co-authored-by: Arpad Müller <arpad-m@users.noreply.github.com>
Only notable change is including neondatabase/autoscaling#523, which we
hope will help with making sure that TCP connections are properly
terminated before shutdown (which hopefully fixes a leak in the
pageserver).
## Problem
We didn't have a Postgres 16 snapshot of data to run compatibility tests
on, but now we have it (since the release).
## Summary of changes
- remove `@skip_on_postgres(PgVersion.V16, ...)` from compatibility
tests
this should allow test
test_delete_tenant_exercise_crash_safety_failpoints with
debug-pg16-Check.RETRY_WITH_RESTART-mock_s3-tenant-delete-before-remove-timelines-dir-True
to pass more reliably.
The test is still flaky, perhaps more after #5233, see #3831.
Do one more `timeline_checkpoint` *after* shutting down safekeepers
*before* shutting down pageserver. Put more effort into not compacting
or creating image layers.
With the addition of the "stateful event verification" the
test_consumption_metrics.py is now too crowded. Split it up for
pageserver and proxy.
Split from #5297.
Write collected metrics to disk to recover previously sent metrics on
restart.
Recover the previously collected metrics during startup, send them over
at right time
- send cached synthetic size before actual is calculated
- when `last_record_lsn` rolls back on startup
- stay at last sent `written_size` metric
- send `written_size_delta_bytes` metric as 0
Add test support: stateful verification of events in python tests.
Fixes: #5206
Cc: #5175 (loggings, will be enhanced in follow-up)
Split off from #5297.
There should be no functional changes here:
- refactor tenant metric "production" like previously timeline, allows
unit testing, though not interesting enough yet to test
- introduce type aliases for tuples
- extra refactoring for `collect`, was initially thinking it was useful
but will do a inline later
- shorter binding names
- support for future allocation reuse quests with IdempotencyKey
- move code out of tokio::select to make it rustfmt-able
- generification, allow later replacement of `&'static str` with enum
- add tests that assert sent event contents exactly
## Problem
VM should be updated if XLH_LOCK_ALL_FROZEN_CLEARED flags is set in
XLOG_HEAP_LOCK,XLOG_HEAP_2_LOCK_UPDATED WAL records
## Summary of changes
Add handling of this records in walingest.rs
## Checklist before requesting a review
- [ ] I have performed a self-review of my code.
- [ ] If it is a core feature, I have added thorough tests.
- [ ] Do we need to implement analytics? if so did you add the relevant
metrics to the dashboard?
- [ ] If this PR requires public announcement, mark it with
/release-notes label and add several sentences in this section.
## Checklist before merging
- [ ] Do not forget to reformat commit message to not include the above
checklist
---------
Co-authored-by: Konstantin Knizhnik <knizhnik@neon.tech>
It was utterly broken on v15 before commit 83e7e5dbbd, which fixed the
incorrect definition of XLOG_DBASE_CREATE_WAL_LOG. We never noticed
because we had no tests for it.
## Problem
In many places in test code, paths are built manually from what
NeonEnv.tenant_dir and NeonEnv.timeline_dir could do.
## Summary of changes
1. NeonEnv.tenant_dir and NeonEnv.timeline_dir moved under class
NeonPageserver as the path they use is per-pageserver instance.
2. Used these everywhere to replace manual path building
Closes#5258
---------
Signed-off-by: Rahul Modpur <rmodpur2@gmail.com>
## Problem
See https://neondb.slack.com/archives/C05L7D1JAUS/p1694614585955029https://www.notion.so/neondatabase/Duplicate-key-issue-651627ce843c45188fbdcb2d30fd2178
## Summary of changes
Swap old/new block references
## Checklist before requesting a review
- [ ] I have performed a self-review of my code.
- [ ] If it is a core feature, I have added thorough tests.
- [ ] Do we need to implement analytics? if so did you add the relevant
metrics to the dashboard?
- [ ] If this PR requires public announcement, mark it with
/release-notes label and add several sentences in this section.
## Checklist before merging
- [ ] Do not forget to reformat commit message to not include the above
checklist
---------
Co-authored-by: Konstantin Knizhnik <knizhnik@neon.tech>
Co-authored-by: Heikki Linnakangas <heikki@neon.tech>
## Problem
See https://neondb.slack.com/archives/C05L7D1JAUS/p1694614585955029https://www.notion.so/neondatabase/Duplicate-key-issue-651627ce843c45188fbdcb2d30fd2178
## Summary of changes
Swap old/new block references
## Checklist before requesting a review
- [ ] I have performed a self-review of my code.
- [ ] If it is a core feature, I have added thorough tests.
- [ ] Do we need to implement analytics? if so did you add the relevant
metrics to the dashboard?
- [ ] If this PR requires public announcement, mark it with
/release-notes label and add several sentences in this section.
## Checklist before merging
- [ ] Do not forget to reformat commit message to not include the above
checklist
---------
Co-authored-by: Konstantin Knizhnik <knizhnik@neon.tech>
Co-authored-by: Heikki Linnakangas <heikki@neon.tech>
## Problem
- `gh pr list` fails with `unknown argument "main"; please quote all
values that have spaces due to using a variable with the wrong name
- `permissions: write-all` are too wide for the job
## Summary of changes
- For variable name `HEAD` -> `BRANCH`
- Grant only required permissions for each job
---------
Co-authored-by: Joonas Koivunen <joonas@neon.tech>
Refactor tests to have less globals.
This will allow to hopefully write more complex tests for our new metric
collection requirements in #5297. Includes reverted work from #4761
related to test globals.
Co-authored-by: Alexander Bayandin <alexander@neon.tech>
Co-authored-by: MMeent <matthias@neon.tech>
## Problem
There was a bug in lfc_ensure_opened which actually disables LFC
## Summary of changes
Return true ifLFC file is normally opened
## Checklist before requesting a review
- [ ] I have performed a self-review of my code.
- [ ] If it is a core feature, I have added thorough tests.
- [ ] Do we need to implement analytics? if so did you add the relevant
metrics to the dashboard?
- [ ] If this PR requires public announcement, mark it with
/release-notes label and add several sentences in this section.
## Checklist before merging
- [ ] Do not forget to reformat commit message to not include the above
checklist
Co-authored-by: Konstantin Knizhnik <knizhnik@neon.tech>
- pagestore_smgr.c had unnecessary WALSync() (see #5287 )
- Compute node dockerfile didn't build the neon_rmgr extension
- Add PostgreSQL 16 image to docker-compose tests
- Fix issue with high CPU usage in Safekeeper due to a bug in WALSender
Co-authored-by: Alexander Bayandin <alexander@neon.tech>
## Problem
If @github-actions creates release PR, the CI pipeline is not triggered
(but we have `release-notify.yml` workflow that we expect to run on this
event).
I suspect this happened because @github-actions is not a repository
member.
Ref
https://github.com/neondatabase/neon/pull/5283#issuecomment-1715209291
## Summary of changes
- Use `CI_ACCESS_TOKEN` to create a PR
- Use `gh` instead of `thomaseizinger/create-pull-request`
- Restrict permissions for GITHUB_TOKEN to `contents: write` only
(required for `git push`)
## Problem
`ci-run/pr-*` branches (and attached PRs) should be deleted
automatically when their parent PRs get closed.
But there are not
## Summary of changes
- Fix if-condition
## Problem
We don't have this instruction written anywhere but in internal Slack
## Summary of changes
- Add `How to run a CI pipeline on Pull Requests from external
contributors` section to `CONTRIBUTING.md`
---------
Co-authored-by: Arpad Müller <arpad-m@users.noreply.github.com>
Motivation
==========
We observed two "indigestion" events on staging, each shortly after
restarting `pageserver-0.eu-west-1.aws.neon.build`. It has ~8k tenants.
The indigestion manifests as `Timeline::get` calls failing with
`exceeded evict iter limit` .
The error is from `page_cache.rs`; it was unable to find a free page and
hence failed with the error.
The indigestion events started occuring after we started deploying
builds that contained the following commits:
```
[~/src/neon]: git log --oneline c0ed362790caa368aa65ba57d352a2f1562fd6bf..15eaf78083ecff62b7669
091da1a1c8b4f60ebf8
15eaf7808 Disallow block_in_place and Handle::block_on (#5101)
a18d6d9ae Make File opening in VirtualFile async-compatible (#5280)
76cc87398 Use tokio locks in VirtualFile and turn with_file into macro (#5247)
```
The second and third commit are interesting.
They add .await points to the VirtualFile code.
Background
==========
On the read path, which is the dominant user of page cache & VirtualFile
during pageserver restart, `Timeline::get` `page_cache` and VirtualFile
interact as follows:
1. Timeline::get tries to read from a layer
2. This read goes through the page cache.
3. If we have a page miss (which is known to be common after restart),
page_cache uses `find_victim` to find an empty slot, and once it has
found a slot, it gives exclusive ownership of it to the caller through a
`PageWriteGuard`.
4. The caller is supposed to fill the write guard with data from the
underlying backing store, i.e., the layer `VirtualFile`.
5. So, we call into `VirtualFile::read_at`` to fill the write guard.
The `find_victim` method finds an empty slot using a basic
implementation of clock page replacement algorithm.
Slots that are currently in use (`PageReadGuard` / `PageWriteGuard`)
cannot become victims.
If there have been too many iterations, `find_victim` gives up with
error `exceeded evict iter limit`.
Root Cause For Indigestion
==========================
The second and third commit quoted in the "Motivation" section
introduced `.await` points in the VirtualFile code.
These enable tokio to preempt us and schedule another future __while__
we hold the `PageWriteGuard` and are calling `VirtualFile::read_at`.
This was not possible before these commits, because there simply were no
await points that weren't Poll::Ready immediately.
With the offending commits, there is now actual usage of
`tokio::sync::RwLock` to protect the VirtualFile file descriptor cache.
And we __know__ from other experiments that, during the post-restart
"rush", the VirtualFile fd cache __is__ too small, i.e., all slots are
taken by _ongoing_ VirtualFile operations and cannot be victims.
So, assume that VirtualFile's `find_victim_slot`'s
`RwLock::write().await` calls _will_ yield control to the executor.
The above can lead to the pathological situation if we have N runnable
tokio tasks, each wanting to do `Timeline::get`, but only M slots, N >>
M.
Suppose M of the N tasks win a PageWriteGuard and get preempted at some
.await point inside `VirtualFile::read_at`.
Now suppose tokio schedules the remaining N-M tasks for fairness, then
schedules the first M tasks again.
Each of the N-M tasks will run `find_victim()` until it hits the
`exceeded evict iter limit`.
Why? Because the first M tasks took all the slots and are still holding
them tight through their `PageWriteGuard`.
The result is massive wastage of CPU time in `find_victim()`.
The effort to find a page is futile, but each of the N-M tasks still
attempts it.
This delays the time when tokio gets around to schedule the first M
tasks again.
Eventually, tokio will schedule them, they will make progress, fill the
`PageWriteGuard`, release it.
But in the meantime, the N-M tasks have already bailed with error
`exceeded evict iter limit`.
Eventually, higher level mechanisms will retry for the N-M tasks, and
this time, there won't be as many concurrent tasks wanting to do
`Timeline::get`.
So, it will shake out.
But, it's a massive indigestion until then.
This PR
=======
This PR reverts the offending commits until we find a proper fix.
```
Revert "Use tokio locks in VirtualFile and turn with_file into macro (#5247)"
This reverts commit 76cc87398c.
Revert "Make File opening in VirtualFile async-compatible (#5280)"
This reverts commit a18d6d9ae3.
```
This adds PostgreSQL 16 as a vendored postgresql version, and adapts the
code to support this version.
The important changes to PostgreSQL 16 compared to the PostgreSQL 15
changeset include the addition of a neon_rmgr instead of altering Postgres's
original WAL format.
Co-authored-by: Alexander Bayandin <alexander@neon.tech>
Co-authored-by: Heikki Linnakangas <heikki@neon.tech>
The sequence that can lead to a deadlock:
1. DELETE request gets all the way to `tenant.shutdown(progress,
false).await.is_err() ` , while holding TENANTS.read()
2. POST request for tenant creation comes in, calls `tenant_map_insert`,
it does `let mut guard = TENANTS.write().await;`
3. Something that `tenant.shutdown()` needs to wait for needs a
`TENANTS.read().await`.
The only case identified in exhaustive manual scanning of the code base
is this one:
Imitate size access does `get_tenant().await`, which does
`TENANTS.read().await` under the hood.
In the above case (1) waits for (3), (3)'s read-lock request is queued
behind (2)'s write-lock, and (2) waits for (1).
Deadlock.
I made a reproducer/proof-that-above-hypothesis-holds in
https://github.com/neondatabase/neon/pull/5281 , but, it's not ready for
merge yet and we want the fix _now_.
fixes https://github.com/neondatabase/neon/issues/5284
The sequence that can lead to a deadlock:
1. DELETE request gets all the way to `tenant.shutdown(progress,
false).await.is_err() ` , while holding TENANTS.read()
2. POST request for tenant creation comes in, calls `tenant_map_insert`,
it does `let mut guard = TENANTS.write().await;`
3. Something that `tenant.shutdown()` needs to wait for needs a
`TENANTS.read().await`.
The only case identified in exhaustive manual scanning of the code base
is this one:
Imitate size access does `get_tenant().await`, which does
`TENANTS.read().await` under the hood.
In the above case (1) waits for (3), (3)'s read-lock request is queued
behind (2)'s write-lock, and (2) waits for (1).
Deadlock.
I made a reproducer/proof-that-above-hypothesis-holds in
https://github.com/neondatabase/neon/pull/5281 , but, it's not ready for
merge yet and we want the fix _now_.
fixes https://github.com/neondatabase/neon/issues/5284
## Problem
Previously, we were using `observe_closure_duration` in `VirtualFile`
file opening code, but this doesn't support async open operations, which
we want to use as part of #4743.
## Summary of changes
* Move the duration measurement from the `with_file` macro into a
`observe_duration` macro.
* Some smaller drive-by fixes to replace the old strings with the new
variant names introduced by #5273
Part of #4743, follow-up of #5247.
## Problem
For #4743, we want to convert everything up to the actual I/O operations
of `VirtualFile` to `async fn`.
## Summary of changes
This PR is the last change in a series of changes to `VirtualFile`:
#5189, #5190, #5195, #5203, and #5224.
It does the last preparations before the I/O operations are actually
made async. We are doing the following things:
* First, we change the locks for the file descriptor cache to tokio's
locks that support Send. This is important when one wants to hold locks
across await points (which we want to do), otherwise the Future won't be
Send. Also, one shouldn't generally block in async code as executors
don't like that.
* Due to the lock change, we now take an approach for the `VirtualFile`
destructors similar to the one proposed by #5122 for the page cache, to
use `try_write`. Similarly to the situation in the linked PR, one can
make an argument that if we are in the destructor and the slot has not
been reused yet, we are the only user accessing the slot due to owning
the lock mutably. It is still possible that we are not obtaining the
lock, but the only cause for that is the clock algorithm touching the
slot, which should be quite an unlikely occurence. For the instance of
`try_write` failing, we spawn an async task to destroy the lock. As just
argued however, most of the time the code path where we spawn the task
should not be visited.
* Lastly, we split `with_file` into a macro part, and a function part
that contains most of the logic. The function part returns a lock
object, that the macro uses. The macro exists to perform the operation
in a more compact fashion, saving code from putting the lock into a
variable and then doing the operation while measuring the time to run
it. We take the locks approach because Rust has no support for async
closures. One can make normal closures return a future, but that
approach gets into lifetime issues the moment you want to pass data to
these closures via parameters that has a lifetime (captures work). For
details, see
[this](https://smallcultfollowing.com/babysteps/blog/2023/03/29/thoughts-on-async-closures/)
and
[this](https://users.rust-lang.org/t/function-that-takes-an-async-closure/61663)
link. In #5224, we ran into a similar problem with the `test_files`
function, and we ended up passing the path and the `OpenOptions`
by-value instead of by-ref, at the expense of a few extra copies. This
can be done as the data is cheaply copyable, and we are in test code.
But here, we are not, and while `File::try_clone` exists, it [issues
system calls
internally](1e746d7741/library/std/src/os/fd/owned.rs (L94-L111)).
Also, it would allocate an entirely new file descriptor, something that
the fd cache was built to prevent.
* We change the `STORAGE_IO_TIME` metrics to support async.
Part of #4743.
Introduce the `StorageIoOperation` enum, `StorageIoTime` struct, and
`STORAGE_IO_TIME_METRIC` static which provides lockless access to
histograms consumed by `VirtualFile`.
Closes#5131
Co-authored-by: Joonas Koivunen <joonas@neon.tech>
Assorted flakyness fixes from #5198, might not be flaky on `main`.
Migrate some tests using neon_simple_env to just neon_env_builder and
using initial_tenant to make flakyness understanding easier. (Did not
understand the flakyness of
`test_timeline_create_break_after_uninit_mark`.)
`test_download_remote_layers_api` is flaky because we have no atomic
"wait for WAL, checkpoint, wait for upload and do not receive any more
WAL".
`test_tenant_size` fixes are just boilerplate which should had always
existed; we should wait for the tenant to be active. similarly for
`test_timeline_delete`.
`test_timeline_size_post_checkpoint` fails often for me with reading
zero from metrics. Give it a few attempts.
## Problem
Detaching a tenant can involve many thousands of local filesystem
metadata writes, but the control plane would benefit from us not
blocking detach/delete responses on these.
## Summary of changes
After rename of local tenant directory ack tenant detach and delete
tenant directory in background
#5183
---------
Signed-off-by: Rahul Modpur <rmodpur2@gmail.com>
## Problem
Another thing I overlooked regarding'approved-for-ci-run`:
- When we create a PR, the action is associated with @vipvap and this
triggers the pipeline — this is good.
- When we update the PR by force-pushing to the branch, the action is
associated with @github-actions, which doesn't trigger a pipeline — this
is bad.
Initially spotted in #5239 / #5211
([link](https://github.com/neondatabase/neon/actions/runs/6122249456/job/16633919558?pr=5239))
— `check-permissions` should not fail.
## Summary of changes
- Use `CI_ACCESS_TOKEN` to check out the repo (I expect this token will
be reused in the following `git push`)
## Problem
When PR `ci-run/pr-*` is created the GitHub Autocomment with test
results are supposed to be posted to the original PR, currently, this
doesn't work.
I created this PR from a personal fork to debug and fix the issue.
## Summary of changes
- `scripts/comment-test-report.js`: use `pull_request.head` instead of
`pull_request.base` 🤦
## Problem
Add a CI pipeline that checks GitHub Workflows with
https://github.com/rhysd/actionlint (it uses `shellcheck` for shell
scripts in steps)
To run it locally: `SHELLCHECK_OPTS=--exclude=SC2046,SC2086 actionlint`
## Summary of changes
- Add `.github/workflows/actionlint.yml`
- Fix actionlint warnings
Some VMs, when already scaled up as much as possible, end up spamming
the autoscaler-agent with upscale requests that will never be fulfilled.
If postgres is using memory greater than the cgroup's memory.high, it
can emit new memory.high events 1000 times per second, which... just
means unnecessary load on the rest of the system.
This changes the vm-monitor so that we skip sending upscale requests if
we already sent one within the last second, to avoid spamming the
autoscaler-agent. This matches previous behavior that the vm-informant
hand.
## Problem
This PR creates a GitHub release from a release tag with an
autogenerated changelog: https://github.com/neondatabase/neon/releases
## Summary of changes
- Call GitHub API to create a release
See #5001
No space is what's expected if we're at size limit.
Of course if SK incorrectly returned "no space", the availability check
wouldn't fire.
But users would notice such a bug quite soon anyways.
So ignoring "no space" is the right trade-off.
## Problem
## Summary of changes
## Checklist before requesting a review
- [ ] I have performed a self-review of my code.
- [ ] If it is a core feature, I have added thorough tests.
- [ ] Do we need to implement analytics? if so did you add the relevant
metrics to the dashboard?
- [ ] If this PR requires public announcement, mark it with
/release-notes label and add several sentences in this section.
## Checklist before merging
- [ ] Do not forget to reformat commit message to not include the above
checklist
---------
Co-authored-by: Konstantin Knizhnik <knizhnik@neon.tech>
Co-authored-by: Joonas Koivunen <joonas@neon.tech>
refer #5208
## Problem
See
https://neondb.slack.com/archives/C03H1K0PGKH/p1693938336062439?thread_ts=1693928260.704799&cid=C03H1K0PGKH#5208 disable LFC forever in case of error. It is not good because the
problem causing this error (for example ENOSPC) can be resolved anti
will be nice to reenable it after fixing.
Also #5208 disables LFC locally in one backend. But other backends may
still see corrupted data.
It should not cause problems right now with "permission denied" error
because there should be no backend which is able to normally open LFC.
But in case of out-of-disk-space error, other backend can read corrupted
data.
## Summary of changes
1. Cleanup hash table after error to prevent access to stale or
corrupted data
2. Perform disk write under exclusive lock (hoping it will not affect
performance because usually write just copy data from user to system
space)
3. Use generations to prevent access to stale data in lfc_read
## Checklist before requesting a review
- [ ] I have performed a self-review of my code.
- [ ] If it is a core feature, I have added thorough tests.
- [ ] Do we need to implement analytics? if so did you add the relevant
metrics to the dashboard?
- [ ] If this PR requires public announcement, mark it with
/release-notes label and add several sentences in this section.
## Checklist before merging
- [ ] Do not forget to reformat commit message to not include the above
checklist
---------
Co-authored-by: Konstantin Knizhnik <knizhnik@neon.tech>
I forgot a `str(...)` conversion in #5243. This lead to log lines such
as:
```
Using fs root 'PosixPath('/tmp/test_output/test_backward_compatibility[debug-pg14]/compatibility_snapshot/repo/local_fs_remote_storage/pageserver')' as a remote storage
```
This surprisingly works, creating hierarchy of under current working
directory (`repo_dir` for tests):
- `PosixPath('`
- `tmp` .. up until .. `local_fs_remote_storage`
- `pageserver')`
It should not work but right now test_compatibility.py tests finds local
metadata and layers, which end up used. After #5172 when remote storage
is the source of truth it will no longer work.
## Problem
A bunch of fixes for different test-related things
## Summary of changes
- Fix test_runner/pg_clients (`subprocess_capture` return value has
changed)
- Do not run create-test-report if check-permissions failed for not
cancelled jobs
- Fix Code Coverage comment layout after flaky tests. Add another
healing "\n"
- test_compatibility: add an instruction for local run
Co-authored-by: Joonas Koivunen <joonas@neon.tech>
## Problem
Currently our testing environment only supports running a single
pageserver at a time. This is insufficient for testing failover and
migrations.
- Dependency of writing tests for #5207
## Summary of changes
- `neon_local` and `neon_fixture` now handle multiple pageservers
- This is a breaking change to the `.neon/config` format: any local
environments will need recreating
- Existing tests continue to work unchanged:
- The default number of pageservers is 1
- `NeonEnv.pageserver` is now a helper property that retrieves the first
pageserver if there is only one, else throws.
- Pageserver data directories are now at `.neon/pageserver_{n}` where n
is 1,2,3...
- Compatibility tests get some special casing to migrate neon_local
configs: these are not meant to be backward/forward compatible, but they
were treated that way by the test.
See
https://neondb.slack.com/archives/C03H1K0PGKH/p1692550646191429
## Problem
Build index concurrently is writing WAL outside transaction.
`backpressure_throttling_impl` doesn't perform throttling for read-only
transactions (not assigned XID).
It cause huge write lag which can cause large delay of accessing the
table.
## Summary of changes
Looks at `PROC_IN_SAFE_IC` in process state set during concurrent index
build.
## Checklist before requesting a review
- [ ] I have performed a self-review of my code.
- [ ] If it is a core feature, I have added thorough tests.
- [ ] Do we need to implement analytics? if so did you add the relevant
metrics to the dashboard?
- [ ] If this PR requires public announcement, mark it with
/release-notes label and add several sentences in this section.
## Checklist before merging
- [ ] Do not forget to reformat commit message to not include the above
checklist
---------
Co-authored-by: Konstantin Knizhnik <knizhnik@neon.tech>
Co-authored-by: Heikki Linnakangas <heikki@neon.tech>
Prepare to upgrade rust version to latest stable.
- `rustfmt` has learned to format `let irrefutable = $expr else { ...
};` blocks
- There's a new warning about virtual (workspace) crate resolver, picked
the latest resolver as I suspect everyone would expect it to be the
latest; should not matter anyways
- Some new clippies, which seem alright
Remote storage cleanup split from #5198:
- pageserver, extensions, and safekeepers now have their separate remote
storage
- RemoteStorageKind has the configuration code
- S3Storage has the cleanup code
- with MOCK_S3, pageserver, extensions, safekeepers use different
buckets
- with LOCAL_FS, `repo_dir / "local_fs_remote_storage" / $user` is used
as path, where $user is `pageserver`, `safekeeper`
- no more `NeonEnvBuilder.enable_xxx_remote_storage` but one
`enable_{pageserver,extensions,safekeeper}_remote_storage`
Should not have any real changes. These will allow us to default to
`LOCAL_FS` for pageserver on the next PR, remove
`RemoteStorageKind.NOOP`, work towards #5172.
Co-authored-by: Alexander Bayandin <alexander@neon.tech>
## Problem
`test_runner/performance/test_startup.py::test_startup` started to fail
more frequently because of the timeout.
Let's increase the timeout to see the failures on the perf dashboard.
## Summary of changes
- Increase timeout for`test_startup` from 600 to 900 seconds
The v1.4.0 includes changes to make it compile with PostgreSQL 16. The
commit log doesn't call it out explicitly, but I tested it manually.
v1.4.0 includes some new functions, but I tested manually that the the
v1.3.1 functionality works with the v1.4.0 version of the library. That
means that this doesn't break existing installations. Users can do
"ALTER EXTENSION hypopg UPDATE" if they want to use the new v1.4.0
functionality, but they don't have to.
This includes PostgreSQL 16 support. No other changes, really.
The extension version in the upstream was changed from 2.17 to 2.18,
however, there is no difference between the catalog objects. So if you
had installed 2.17 previously, it will continue to work. You can run
"ALTER EXTENSION hll UPDATE", but all it will do is update the version
number in the pg_extension table.
## Problem
Once we use async file system APIs for `VirtualFile`, these functions
will also need to be async fn.
## Summary of changes
Makes the functions `open, open_with_options, create,sync_all,with_file`
of `VirtualFile` async fn, including all functions that call it. Like in
the prior PRs, the actual I/O operations are not using async APIs yet,
as per request in the #4743 epic.
We switch towards not using `VirtualFile` in the par_fsync module,
hopefully this is only temporary until we can actually do fully async
I/O in `VirtualFile`. This might cause us to exhaust fd limits in the
tests, but it should only be an issue for the local developer as we have
high ulimits in prod.
This PR is a follow-up of #5189, #5190, #5195, and #5203. Part of #4743.
It's a good idea to keep up-to-date in general. One noteworthy change is
that PostGIS 3.3.3 adds support for PostgreSQL v16. We'll need that.
PostGIS 3.4.0 has already been released, and we should consider
upgrading to that. However, it's a major upgrade and requires running
"SELECT postgis_extensions_upgrade();" in each database, to upgrade the
catalogs. I don't want to deal with that right now.
## Problem
We likely need this to support Postgres 16
It's also been asked by a user
https://github.com/neondatabase/neon/discussions/5042
The latest version is 3.2.0, but it requires some changes in the build
script (which I haven't checked, but it didn't work right away)
## Summary of changes
```
3.1.8 2023-08-01
- force v8 to compile in release mode
3.1.7 2023-06-26
- fix byteoffset issue with arraybuffers
- support postgres 16 beta
3.1.6 2023-04-08
- fix crash issue on fetch apply
- fix interrupt issue
```
From https://github.com/plv8/plv8/blob/v3.1.8/Changes
## Problem
We've got `approved-for-ci-run` to work 🎉
But it's still a bit rough, this PR should improve the UX for external
contributors.
## Summary of changes
- `build_and_test.yml`: add `check-permissions` job, which fails if PR is
created from a fork. Make all jobs in the workflow to be dependant on
`check-permission` to fail fast
- `approved-for-ci-run.yml`: add `cleanup` job to close `ci-run/pr-*`
PRs and delete linked branches when the parent PR is closed
- `approved-for-ci-run.yml`: fix the layout for the `ci-run/pr-*` PR
description
- GitHub Autocomment: add a comment with tests result to the original PR
(instead of a PR from `ci-run/pr-*` )
Add a `walreceiver_state` field to `TimelineInfo` (response of `GET /v1/tenant/:tenant_id/timeline/:timeline_id`) and while doing that, refactor out a common `Timeline::walreceiver_state(..)`. No OpenAPI changes, because this is an internal debugging addition.
Fixes#3115.
Co-authored-by: Joonas Koivunen <joonas.koivunen@gmail.com>
It was easy to interpret comment in the page cache initialization code
to be about justifying why we leak here at all, not just why this
specific type of leaking is done (which the comment was actually meant
to describe).
See
https://github.com/neondatabase/neon/pull/5125#discussion_r1308445993
---------
Co-authored-by: Joonas Koivunen <joonas@neon.tech>
## Problem
- `SCALE: unbound variable` from
https://github.com/neondatabase/neon/pull/5079
- The layout of the GitHub auto-comment is broken if the code coverage
section follows flaky test section from
https://github.com/neondatabase/neon/pull/4999
## Summary of changes
- `benchmarking.yml`: Rename `SCALE` to `TEST_OLAP_SCALE`
- `comment-test-report.js`: Add an extra new-line before Code coverage
section
## Problem
When the next release is coming, we want to let everyone know about it by
posting a message to the Slack channel with a list of commits.
## Summary of changes
- `.github/workflows/release-notify.yml` is added
- the workflow sends a message to
`vars.SLACK_UPCOMING_RELEASE_CHANNEL_ID` (or
[#test-release-notifications](https://neondb.slack.com/archives/C05QQ9J1BRC)
if not configured)
- On each PR update, the workflow updates the list of commits in the
message (it doesn't send additional messages)
## Problem
We want to convert the `VirtualFile` APIs to async fn so that we can
adopt one of the async I/O solutions.
## Summary of changes
This PR is a follow-up of #5189, #5190, and #5195, and does the
following:
* Move the used `Write` trait functions of `VirtualFile` into inherent
functions
* Add optional buffering to `WriteBlobWriter`. The buffer is discarded
on drop, similarly to how tokio's `BufWriter` does it: drop is neither
async nor does it support errors.
* Remove the generics by `Write` impl of `WriteBlobWriter`, alwaays
using `VirtualFile`
* Rename `WriteBlobWriter` to `BlobWriter`
* Make various functions in the write path async, like
`VirtualFile::{write,write_all}`.
Part of #4743.
## Problem
`CI_ACCESS_TOKEN` has quite limited access (which is good), but this
doesn't allow it to remove labels from PRs (which is bad)
## Summary of changes
- Use `GITHUB_TOKEN` to remove labels
- Use `CI_ACCESS_TOKEN` to create PRs
## Problem
- #5050
Closes: https://github.com/neondatabase/neon/issues/5136
## Summary of changes
- A new configuration property `control_plane_api` controls other
functionality in this PR: if it is unset (default) then everything still
works as it does today.
- If `control_plane_api` is set, then on startup we call out to control
plane `/re-attach` endpoint to discover our attachments and their
generations. If an attachment is missing from the response we implicitly
detach the tenant.
- Calls to pageserver `/attach` API may include a `generation`
parameter. If `control_plane_api` is set, then this parameter is
mandatory.
- RemoteTimelineClient's loading of index_part.json is generation-aware,
and will try to load the index_part with the most recent generation <=
its own generation.
- The `neon_local` testing environment now includes a new binary
`attachment_service` which implements the endpoints that the pageserver
requires to operate. This is on by default if running `cargo neon` by
hand. In `test_runner/` tests, it is off by default: existing tests
continue to run with in the legacy generation-less mode.
Caveats:
- The re-attachment during startup assumes that we are only re-attaching
tenants that have previously been attached, and not totally new tenants
-- this relies on the control plane's attachment logic to keep retrying
so that we should eventually see the attach API call. That's important
because the `/re-attach` API doesn't tell us which timelines we should
attach -- we still use local disk state for that. Ref:
https://github.com/neondatabase/neon/issues/5173
- Testing: generations are only enabled for one integration test right
now (test_pageserver_restart), as a smoke test that all the machinery
basically works. Writing fuller tests that stress tenant migration will
come later, and involve extending our test fixtures to deal with
multiple pageservers.
- I'm not in love with "attachment_service" as a name for the neon_local
component, but it's not very important because we can easily rename
these test bits whenever we want.
- Limited observability when in re-attach on startup: when I add
generation validation for deletions in a later PR, I want to wrap up the
control plane API calls in some small client class that will expose
metrics for things like errors calling the control plane API, which will
act as a strong red signal that something is not right.
Co-authored-by: Christian Schwarz <christian@neon.tech>
Co-authored-by: Joonas Koivunen <joonas@neon.tech>
## Problem
Pull Requests created by GitHub Actions bot doesn't have access to
secrets, so we need to use our bot for it to auto-trigger a tests run
See previous PRs #4663, #5210, #5212
## Summary of changes
- Use our bot to create PRs
## Problem
- Scrubber's `tidy` command requires presence of a control plane
- Scrubber has no tests at all
## Summary of changes
- Add re-usable async streams for reading metadata from a bucket
- Add a `scan-metadata` command that reads from those streams and calls
existing `checks.rs` code to validate metadata, then returns a summary
struct for the bucket. Command returns nonzero status if errors are
found.
- Add an `enable_scrub_on_exit()` function to NeonEnvBuilder so that
tests using remote storage can request to have the scrubber run after
they finish
- Enable remote storarge and scrub_on_exit in test_pageserver_restart
and test_pageserver_chaos
This is a "toe in the water" of the overall space of validating the
scrubber. Later, we should:
- Enable scrubbing at end of tests using remote storage by default
- Make the success condition stricter than "no errors": tests should
declare what tenants+timelines they expect to see in the bucket (or
sniff these from the functions tests use to create them) and we should
require that the scrubber reports on these particular tenants/timelines.
The `tidy` command is untouched in this PR, but it should be refactored
later to use similar async streaming interface instead of the current
batch-reading approach (the streams are faster with large buckets), and
to also be covered by some tests.
---------
Co-authored-by: Joonas Koivunen <joonas@neon.tech>
Co-authored-by: Alexander Bayandin <alexander@neon.tech>
Co-authored-by: Christian Schwarz <christian@neon.tech>
Co-authored-by: Conrad Ludgate <conrad@neon.tech>
## Problem
It's hard to find out which DB size we use for OLAP benchmarks (TPC-H in
particular).
This PR adds handling of `TEST_OLAP_SCALE` env var, which is get added
to a test name as a parameter.
This is required for performing larger periodic benchmarks.
## Summary of changes
- Handle `TEST_OLAP_SCALE` in
`test_runner/performance/test_perf_olap.py`
- Set `TEST_OLAP_SCALE` in `.github/workflows/benchmarking.yml` to a
TPC-H scale
Fixes#3830 by adding the `#[cfg(not(feature = "testing"))]` attribute
to unnecessary loggings in `pageserver/src/tenant/tasks.rs`.
Co-authored-by: Joonas Koivunen <joonas@neon.tech>
## Problem
Continuation of #4663, #5210
We're still getting an error:
```
GraphQL: Resource not accessible by integration (removeLabelsFromLabelable)
```
## Summary of changes
- trigger `approved-for-ci-run.yml` workflow on `pull_request_target`
instead of `pull_request`
Fix issue where updating the size of the Local File Cache could lead to
invalid reads:
## Problem
LFC cache can get re-enabled when lfc_max_size is set, e.g. through an
autoscaler configuration, or PostgreSQL not liking us setting the
variable.
1. initialize: LFC enabled (lfc_size_limit > 0; lfc_desc = 0)
2. Open LFC file fails, lfc_desc = -1. lfc_size_limit is set to 0;
3. lfc_size_limit is updated by autoscaling to >0
4. read() now thinks LFC is enabled (size_limit > 0) and lfc_desc is
valid, but doesn't try to read from the invalid file handle and thus
doesn't update the buffer content with the page's data, but does think
the data was read...
Any buffer we try to read from local file cache is essentially
uninitialized memory. Those are likely 0-bytes, but might potentially be
any old buffer that was previously read from or flushed to disk.
Fix this by adding a more definitive disable flag, plus better invalid state handling.
## Problem
When a remote custom extension build fails, it looks a bit confusing on
neon CI:
- `trigger-custom-extensions-build` is green
- `wait-for-extensions-build` is red
- `build-and-upload-extensions` is red
But to restart the build (to get everything green), you need to restart
the only passed `trigger-custom-extensions-build`.
## Summary of changes
- Merge `trigger-custom-extensions-build` and
`wait-for-extensions-build` jobs into
`trigger-custom-extensions-build-and-wait`
## Problem
We want to convert the `VirtualFile` APIs to async fn so that we can
adopt one of the async I/O solutions.
## Summary of changes
Convert the following APIs of `VirtualFile` to async fn (as well as all
of the APIs calling it):
* `VirtualFile::seek`
* `VirtualFile::metadata`
* Also, prepare for deletion of the write impl by writing the summary to
a buffer before writing it to disk, as suggested in
https://github.com/neondatabase/neon/issues/4743#issuecomment-1700663864
. This change adds an additional warning for the case when the summary
exceeds a block. Previously, we'd have silently corrupted data in this
(unlikely) case.
* `WriteBlobWriter::write_blob`, in preparation for making
`VirtualFile::write_all` async.
A set of changes to enable neon to work in IPv6 environments. The
changes are backward-compatible but allow to deploy neon even to
IPv6-only environments:
- bind to both IPv4 and IPv6 interfaces
- allow connections to Postgres from IPv6 interface
- parse the address from control plane that could also be IPv6
## Problem
`VirtualFile` does both reading and writing, and it would be nice if
both could be converted to async, so that it doesn't have to support an
async read path and a blocking write path (especially for the locks this
is annoying as none of the lock implementations in std, tokio or
parking_lot have support for both async and blocking access).
## Summary of changes
This PR is some initial work on making the `VirtualFile` APIs async. It
can be reviewed commit-by-commit.
* Introduce the `MaybeVirtualFile` enum to be generic in a test that
compares real files with virtual files.
* Make various APIs of `VirtualFile` async, including `write_all_at`,
`read_at`, `read_exact_at`.
Part of #4743 , successor of #5180.
Co-authored-by: Christian Schwarz <me@cschwarz.com>
## Problem
The `VirtualFile::crashsafe_overwrite` function was introduced by #5186
but it was not turned `async fn` yet. We want to make these functions
async fn as part of #4743.
## Summary of changes
Make `VirtualFile::crashsafe_overwrite` async fn, as well as all the
functions calling it. Don't make anything inside `crashsafe_overwrite`
use async functionalities, as per #4743 instructions.
Also, add rustdoc to `crashsafe_overwrite`.
Part of #4743.
## Problem
If a pageserver crashes partway through deleting a tenant's directory,
it might leave a partial state that confuses a subsequent
startup/attach.
## Summary of changes
Rename tenant directory to a temporary path before deleting.
Timeline deletions already have deletion markers to provide safety.
In future, it would be nice to exploit this to send responses to detach
requests earlier: https://github.com/neondatabase/neon/issues/5183
(part of #4743)
(preliminary to #5180)
This PR adds a special-purpose API to `VirtualFile` for write-once
files.
It adopts it for `save_metadata` and `persist_tenant_conf`.
This is helpful for the asyncification efforts (#4743) and specifically
asyncification of `VirtualFile` because above two functions were the
only ones that needed the VirtualFile to be an `std::io::Write`.
(There was also `manifest.rs` that needed the `std::io::Write`, but, it
isn't used right now, and likely won't be used because we're taking a
different route for crash consistency, see #5172. So, let's remove it.
It'll be in Git history if we need to re-introduce it when picking up
the compaction work again; that's why it was introduced in the first
place).
We can't remove the `impl std::io::Write for VirtualFile` just yet
because of the `BufWriter` in
```rust
struct DeltaLayerWriterInner {
...
blob_writer: WriteBlobWriter<BufWriter<VirtualFile>>,
}
```
But, @arpad-m and I have a plan to get rid of that by extracting the
append-only-ness-on-top-of-VirtualFile that #4994 added to
`EphemeralFile` into an abstraction that can be re-used in the
`DeltaLayerWriterInner` and `ImageLayerWriterInner`.
That'll be another PR.
### Performance Impact
This PR adds more fsyncs compared to before because we fsync the parent
directory every time.
1. For `save_metadata`, the additional fsyncs are unnecessary because we
know that `metadata` fits into a kernel page, and hence the write won't
be torn on the way into the kernel. However, the `metadata` file in
general is going to lose signficance very soon (=> see #5172), and the
NVMes in prod can definitely handle the additional fsync. So, let's not
worry about it.
2. For `persist_tenant_conf`, which we don't check to fit into a single
kernel page, this PR makes it actually crash-consistent. Before, we
could crash while writing out the tenant conf, leaving a prefix of the
tenant conf on disk.
## Problem
Tests using remote storage have manually entered `test_name` parameters,
which:
- Are easy to accidentally duplicate when copying code to make a new
test
- Omit parameters, so don't actually create unique S3 buckets when
running many tests concurrently.
## Summary of changes
- Use the `request` fixture in neon_env_builder fixture to get the test
name, then munge that into an S3 compatible bucket name.
- Remove the explicit `test_name` parameters to enable_remote_storage
For
[#5086](https://github.com/neondatabase/neon/pull/5086#issuecomment-1701331777)
we will require remote storage to be configured in pageserver.
This PR enables `localfs`-based storage for all Rust unit tests.
Changes:
- In `TenantHarness`, set up localfs remote storage for the tenant.
- `create_test_timeline` should mimic what real timeline creation does,
and real timeline creation waits for the timeline to reach remote
storage. With this PR, `create_test_timeline` now does that as well.
- All the places that create the harness tenant twice need to shut down
the tenant before the re-create through a second call to `try_load` or
`load`.
- Without shutting down, upload tasks initiated by/through the first
incarnation of the harness tenant might still be ongoing when the second
incarnation of the harness tenant is `try_load`/`load`ed. That doesn't
make sense in the tests that do that, they generally try to set up a
scenario similar to pageserver stop & start.
- There was one test that recreates a timeline, not the tenant. For that
case, I needed to create a `Timeline::shutdown` method. It's a
refactoring of the existing `Tenant::shutdown` method.
- The remote_timeline_client tests previously set up their own
`GenericRemoteStorage` and `RemoteTimelineClient`. Now they re-use the
one that's pre-created by the TenantHarness. Some adjustments to the
assertions were needed because the assertions now need to account for
the initial image layer that's created by `create_test_timeline` to be
present.
This RFC describes a simple scheme to make layer map updates crash
consistent by leveraging the index_part.json in remote storage. Without
such a mechanism, crashes can induce certain edge cases in which broadly
held assumptions about system invariants don't hold.
The `remote_timeline_client` tests use `#[tokio::test]` and rely on the
fact that the test runtime that is set up by this macro is
single-threaded.
In PR https://github.com/neondatabase/neon/pull/5164, we observed
interesting flakiness with the `upload_scheduling` test case:
it would observe the upload of the third layer (`layer_file_name_3`)
before we did `wait_completion`.
Under the single-threaded-runtime assumption, that wouldn't be possible,
because the test code doesn't await inbetween scheduling the upload
and calling `wait_completion`.
However, RemoteTimelineClient was actually using `BACKGROUND_RUNTIME`.
That means there was parallelism where the tests didn't expect it,
leading to flakiness such as execution of an UploadOp task before
the test calls `wait_completion`.
The most confusing scenario is code like this:
```
schedule upload(A);
wait_completion.await; // B
schedule_upload(C);
wait_completion.await; // D
```
On a single-threaded executor, it is guaranteed that the upload up C
doesn't run before D, because we (the test) don't relinquish control
to the executor before D's `await` point.
However, RemoteTimelineClient actually scheduled onto the
BACKGROUND_RUNTIME, so, `A` could start running before `B` and
`C` could start running before `D`.
This would cause flaky tests when making assertions about the state
manipulated by the operations. The concrete issue that led to discover
of this bug was an assertion about `remote_fs_dir` state in #5164.
## Problem
Currently, the `deploy` job doesn't wait for the custom extension job
(in another repo) and can be started even with failed extensions build.
This PR adds another job that polls the status of the extension build job
and fails if the extension build fails.
## Summary of changes
- Add `wait-for-extensions-build` job, which waits for a custom
extension build in another repo.
## Problem
- https://github.com/neondatabase/neon/issues/5167
## Summary of changes
Accept "will not become active" log line with _either_ Broken or
Stopping state, because we may hit it while in the process of doing the
`/ignore` (earlier in the test than the test expects to see the same
line with Broken)
## Problem
The S3 scrubber currently lives at
https://github.com/neondatabase/s3-scrubber
We don't have tests that use it, and it has copies of some data
structures that can get stale.
## Summary of changes
- Import the s3-scrubber as `s3_scrubber/
- Replace copied_definitions/ in the scrubber with direct access to the
`utils` and `pageserver` crates
- Modify visibility of a few definitions in `pageserver` to allow the
scrubber to use them
- Update scrubber code for recent changes to `IndexPart`
- Update `KNOWN_VERSIONS` for IndexPart and move the definition into
index.rs so that it is easier to keep up to date
As a future refinement, it would be good to pull the remote persistence
types (like IndexPart) out of `pageserver` into a separate library so
that the scrubber doesn't have to link against the whole pageserver, and
so that it's clearer which types need to be public.
Co-authored-by: Kirill Bulatov <kirill@neon.tech>
Co-authored-by: Dmitry Rodionov <dmitry@neon.tech>
Co-authored-by: Arpad Müller <arpad-m@users.noreply.github.com>
## Problem
Test failing on a different ERROR log than it anticipated.
Closes: https://github.com/neondatabase/neon/issues/5148
## Summary of changes
Add the "could not flush frozen layer" error log to the permitted
errors.
## Problem
To implement split brain protection, we need tenants and timelines to be
aware of their current generation, and use it when composing S3 keys.
## Summary of changes
- A `Generation` type is introduced in the `utils` crate -- it is in
this broadly-visible location because it will later be used from
`control_plane/` as well as `pageserver/`. Generations can be a number,
None, or Broken, to support legacy content (None), and Tenants in the
broken state (Broken).
- Tenant, Timeline, and RemoteTimelineClient all get a generation
attribute
- IndexPart's IndexLayerMetadata has a new `generation` attribute.
Legacy layers' metadata will deserialize to Generation::none().
- Remote paths are composed with a trailing generation suffix. If a
generation is equal to Generation::none() (as it currently always is),
then this suffix is an empty string.
- Functions for composing remote storage paths added in
remote_timeline_client: these avoid the way that we currently always
compose a local path and then strip the prefix, and avoid requiring a
PageserverConf reference on functions that want to create remote paths
(the conf is only needed for local paths). These are less DRY than the
old functions, but remote storage paths are a very rarely changing
thing, so it's better to write out our paths clearly in the functions
than to compose timeline paths from tenant paths, etc.
- Code paths that construct a Tenant take a `generation` argument in
anticipation that we will soon load generations on startup before
constructing Tenant.
Until the whole feature is done, we don't want any generation-ful keys
though: so initially we will carry this everywhere with the special
Generation::none() value.
Closes: https://github.com/neondatabase/neon/issues/5135
Co-authored-by: Christian Schwarz <christian@neon.tech>
I've moved it to the API handler in the 589cf1ed2 to do not delay
compute start. Yet, we now skip full configuration and catalog updates
in the most hot path -- waking up suspended compute, and only do it at:
- first start
- start with applying new configuration
- start for availability check
so it doesn't really matter anymore.
The problem with creating the table and test record in the API handler
is that someone can fill up timeline till the logical limit. Then it's
suspended and availability check is scheduled, so it fails.
If table + test row are created at the very beginning, we reserve a 8 KB
page for future checks, which theoretically will last almost forever.
For example, my ~1y old branch still has 8 KB sized test table:
```sql
cloud_admin@postgres=# select pg_relation_size('health_check');
pg_relation_size
------------------
8192
(1 row)
```
---------
Co-authored-by: Anastasia Lubennikova <anastasia@neon.tech>
## Problem
`timeline_layers` was write-only since
b95addddd5
We deployed the version that no longer requires it for deserializing, so
now we can stop including it when serializing.
## Summary of changes
Fully remove `timeline_layers`.
In logs it is confusing to see seqwait timeouts which seemingly arise
from the branched lsn but actually are about the ancestor, leading to
questions like "has the last_record_lsn went back".
Noticed by @problame.
## Summary
A scheme of logical "generation numbers" for pageservers and their
attachments is proposed, along with
changes to the remote storage format to include these generation numbers
in S3 keys.
Using the control plane as the issuer of these generation numbers
enables strong anti-split-brain
properties in the pageserver cluster without implementing a consensus
mechanism directly
in the pageservers.
## Motivation
Currently, the pageserver's remote storage format does not provide a
mechanism for addressing
split brain conditions that may happen when replacing a node during
failover or when migrating
a tenant from one pageserver to another. From a remote storage
perspective, a split brain condition
occurs whenever two nodes both think they have the same tenant attached,
and both can write to S3. This
can happen in the case of a network partition, pathologically long
delays (e.g. suspended VM), or software
bugs.
This blocks robust implementation of failover from unresponsive
pageservers, due to the risk that
the unresponsive pageserver is still writing to S3.
---------
Co-authored-by: Christian Schwarz <christian@neon.tech>
Co-authored-by: Arpad Müller <arpad-m@users.noreply.github.com>
Co-authored-by: Heikki Linnakangas <heikki@neon.tech>
## Problem
`read_blk` does I/O and thus we would like to make it async. We can't
make the function async as long as the `PageReadGuard` returned by
`read_blk` isn't `Send`. The page cache is called by `read_blk`, and
thus it can't be async without `read_blk` being async. Thus, we have a
circular dependency.
## Summary of changes
Due to the circular dependency, we convert both the page cache and
`read_blk` to async at the same time:
We make the page cache use `tokio::sync` synchronization primitives as
those are `Send`. This makes all the places that acquire a lock require
async though, which we then also do. This includes also asyncification
of the `read_blk` function.
Builds upon #4994, #5015, #5056, and #5129.
Part of #4743.
Instead of fixed during the start of replication. To this end, create
term_flush_lsn watch channel similar to commit_lsn one. This allows to continue
recovery streaming if new data appears.
Slightly refactors init: now load_tenant_timelines is also async to properly
init the timeline, but to keep global map lock sync we just acquire it anew for
each timeline.
Recovery task itself is just a stub here.
part of
https://github.com/neondatabase/neon/pull/4875
Part 1 of 2, for moving the file cache onto disk.
Because VMs are created by the control plane (and that's where the
filesystem for the file cache is defined), we can't rely on any kind of
synchronization between releases, so the change needs to be
feature-gated (kind of), with the default remaining the same for now.
See also: neondatabase/cloud#6593
## Problem
We still need to rerun some builds manually because flaky tests weren't
detected automatically.
I found two reasons for it:
- If a test is flaky on a particular build type, on a particular
Postgres version, there's a high chance that this test is flaky on all
configurations, but we don't automatically detect such cases.
- We detect flaky tests only on the main branch, which requires manual
retrigger runs for freshly made flaky tests.
Both of them are fixed in the PR.
## Summary of changes
- Spread flakiness of a single test to all configurations
- Detect flaky tests in all branches (not only in the main)
- Look back only at 7 days of test history (instead of 10)
## Problem
I saw these things while working on #5111.
## Summary of changes
* Add a comment explaining why we use `Vec::leak` instead of
`Vec::into_boxed_slice` plus `Box::leak`.
* Add another comment explaining what `valid` is doing, it wasn't very
clear before.
* Add a function `set_usage_count` to not set it directly.
Before this patch, when dropping an EphemeralFile, we'd scan the entire
`slots` to proactively evict its pages (`drop_buffers_for_immutable`).
This was _necessary_ before #4994 because the page cache was a
write-back cache: we'd be deleting the EphemeralFile from disk after,
so, if we hadn't evicted its pages before that, write-back in
`find_victim` wouldhave failed.
But, since #4994, the page cache is a read-only cache, so, it's safe
to keep read-only data cached. It's never going to get accessed again
and eventually, `find_victim` will evict it.
The only remaining advantage of `drop_buffers_for_immutable` over
relying on `find_victim` is that `find_victim` has to do the clock
page replacement iterations until the count reaches 0,
whereas `drop_buffers_for_immutable` can kick the page out right away.
However, weigh that against the cost of `drop_buffers_for_immutable`,
which currently scans the entire `slots` array to find the
EphemeralFile's pages.
Alternatives have been proposed in #5122 and #5128, but, they come
with their own overheads & trade-offs.
Also, the real reason why we're looking into this piece of code is
that we want to make the slots rwlock async in #5023.
Since `drop_buffers_for_immutable` is called from drop, and there
is no async drop, it would be nice to not have to deal with this.
So, let's just stop doing `drop_buffers_for_immutable` and observe
the performance impact in benchmarks.
Unrelated fixes noticed while integrating #4938.
- Stop leaking future layers in remote storage
- We schedule extra index_part uploads if layer name to be removed was
not actually present
Starts `postgres` in cgroup directly from `compute_ctl` instead of from
`vm-builder`. This is required because the `vm-monitor` cannot be in the
cgroup it is managing. Otherwise, it itself would be frozen when
freezing the cgroup.
Requires https://github.com/neondatabase/cloud/pull/6331, which adds the
`AUTOSCALING` environment variable letting `compute_ctl` know to start
`postgres` in the cgroup.
Requires https://github.com/neondatabase/autoscaling/pull/468, which
prevents `vm-builder` from starting the monitor and putting postgres in
a cgroup. This will require a `VM_BUILDER_VERSION` bump.
## Problem
We were returning Pending when a connection had a notice/notification
(introduced recently in #5020). When returning pending, the runtime
assumes you will call `cx.waker().wake()` in order to continue
processing.
We weren't doing that, so the connection task would get stuck
## Summary of changes
Don't return pending. Loop instead
## Problem
cargo deny lint broken
Links to the CVEs:
[rustsec.org/advisories/RUSTSEC-2023-0052](https://rustsec.org/advisories/RUSTSEC-2023-0052)
[rustsec.org/advisories/RUSTSEC-2023-0053](https://rustsec.org/advisories/RUSTSEC-2023-0053)
One is fixed, the other one isn't so we allow it (for now), to unbreak
CI. Then later we'll try to get rid of webpki in favour of the rustls
fork.
## Summary of changes
```
+ignore = ["RUSTSEC-2023-0052"]
```
## Problem
The `metadata_bytes` field of IndexPart required explicit
deserialization & error checking everywhere it was used -- there isn't
anything special about this structure that should prevent it from being
serialized & deserialized along with the rest of the structure.
## Summary of changes
- Implement Serialize and Deserialize for TimelineMetadata
- Replace IndexPart::metadata_bytes with a simpler `metadata`, that can
be used directly.
---------
Co-authored-by: Arpad Müller <arpad-m@users.noreply.github.com>
## Problem
We were returning Pending when a connection had a notice/notification
(introduced recently in #5020). When returning pending, the runtime
assumes you will call `cx.waker().wake()` in order to continue
processing.
We weren't doing that, so the connection task would get stuck
## Summary of changes
Don't return pending. Loop instead
## Problem
We want to make `read_blk` an async function, but outside of
`async_trait`, which allocates, and nightly features, we can't use async
fn's in traits.
## Summary of changes
* Remove all uses of `BlockReader::read_blk` in favour of using block
cursors, at least where the type of the `BlockReader` is behind a
generic
* Introduce a `BlockReaderRef` enum that lists all implementors of
`BlockReader::read_blk`.
* Remove `BlockReader::read_blk` and move its implementations into
inherent functions on the types instead.
We don't turn `read_blk` into an async fn yet, for that we also need to
modify the page cache. So this is a preparatory PR, albeit an important
one.
Part of #4743.
## Problem
The previous arguments have the monitor listen on `localhost`, which the
informant can connect to since it's also in the VM, but which the agent
cannot. Also, the port is wrong.
## Summary of changes
Listen on `0.0.0.0:10301`
## Problem
The `EphemeralFile::write_blob` function accesses the page cache
internally. We want to require `async` for these accesses in #5023.
## Summary of changes
This removes the implementaiton of the `BlobWriter` trait for
`EphemeralFile` and turns the `write_blob` function into an inherent
function. We can then make it async as well as the `push_bytes`
function. We move the `SER_BUFFER` thread-local into the
`InMemoryLayerInner` so that the same buffer can be accessed by
different threads as the async is (potentially) moved between threads.
Part of #4743, preparation for #5023.
Current implementation first calls `load_layer_map`, which loads all
local layers, cleans up files, leave cleaning up stuff to "second
function". Then the "second function" is finally called, it does not do
the cleanup and some of the first functions setup can torn down. "Second
function" is actually both `reconcile_with_remote` and
`create_remote_layers`.
This change makes it a bit more verbose but in one phase with the
following sub-steps:
1. scan the timeline directory
2. delete extra files
- now including on-demand download files
- fixes#3660
3. recoincile the two sources of layers (directory, index_part)
4. rename_to_backup future layers, short layers
5. create the remaining as layers
Needed by #4938.
It was also noticed that this is blocking code in an `async fn` so just
do it in a `spawn_blocking`, which should be healthy for our startup
times. Other effects includes hopefully halving of `stat` calls; extra
calls which were not done previously are now done for the future layers.
Co-authored-by: Christian Schwarz <christian@neon.tech>
Co-authored-by: John Spray <john@neon.tech>
## Problem
Currently, anything that uses backoff::retry will delay the join of its
task by however long its backoff sleep is, multiplied by its max
retries.
Whenever we call a function that sleeps, we should be passing in a
CancellationToken.
## Summary of changes
- Add a `Cancel` type to backoff::retry that wraps a CancellationToken
and an error `Fn` to generate an error if the cancellation token fires.
- In call sites that already run in a `task_mgr` task, use
`shutdown_token()` to provide the token. In other locations, use a dead
`CancellationToken` to satisfy the interface, and leave a TODO to fix it
up when we broaden the use of explicit cancellation tokens.
This is cherry-picked-then-improved version of release branch commit
4204960942 PR #4861)
The commit
commit 5f8fd640bf
Author: Alek Westover <alek.westover@gmail.com>
Date: Wed Jul 26 08:24:03 2023 -0400
Upload Test Remote Extensions (#4792)
switched to using the release tag instead of `latest`, but,
the `promote-images` job only uploads `latest` to the prod ECR.
The switch to using release tag was good in principle, but,
it broke the release pipeline. So, switch release pipeline
back to using `latest`.
Note that a proper fix should abandon use of `:latest` tag
at all: currently, if a `main` pipeline runs concurrently
with a `release` pipeline, the `release` pipeline may end
up using the `main` pipeline's images.
---------
Co-authored-by: Alexander Bayandin <alexander@neon.tech>
Accidentially giving is_incremental=true for ImageLayers costs a lot of
debugging time. Removes all API which would allow to do that. They can
easily be restored later *when needed*.
Split off from #4938.
When doing global queries in VictoriaMetrics, the per-timeline
histograms make us run into cardinality limits.
We don't want to give them up just yet because we don't
have an alternative for drilling down on timeline-specific
performance issues.
So, add a pre-aggregated histogram and add observations to it
whenever we add observations to the per-timeline histogram.
While we're at it, switch to using a strummed enum for the operation
type names.
#4938 will make on-demand download of layers in compaction possible, so
it's not suitable for our "policy" of no `spawn_blocking(|| ...
Handle::block_on(async { spawn_blocking(...).await })` because this
poses a clear deadlock risk. Nested spawn_blockings are because of the
download using `tokio::fs::File`.
- Remove `spawn_blocking` from caller of `compact_level0_phase1`
- Remove `Handle::block_on` from `compact_level0_phase1` (indentation
change)
- Revert to `AsLayerDesc::layer_desc` usage temporarily (until it
becomes field access in #4938)
## Problem
many duplicate windows crates pollute the cargo deny output
## Summary of changes
we don't build those crates, so remove those targets from being checked
## Problem
cargo deny lint broken
Links to the CVEs:
[rustsec.org/advisories/RUSTSEC-2023-0052](https://rustsec.org/advisories/RUSTSEC-2023-0052)
[rustsec.org/advisories/RUSTSEC-2023-0053](https://rustsec.org/advisories/RUSTSEC-2023-0053)
One is fixed, the other one isn't so we allow it (for now), to unbreak
CI. Then later we'll try to get rid of webpki in favour of the rustls
fork.
## Summary of changes
```
+ignore = ["RUSTSEC-2023-0052"]
```
## Problem
There are some common types that we pass into tenants and timelines as
we construct them, such as remote storage and the broker client.
Currently the list is small, but this is likely to grow -- the deletion
queue PR (#4960) pushed some methods to the point of clippy complaining
they had too many args, because of the extra deletion queue client being
passed around.
There are some shared objects that currently aren't passed around
explicitly because they use a static `once_cell` (e.g.
CONCURRENT_COMPACTIONS), but as we add more resource management and
concurreny control over time, it will be more readable & testable to
pass a type around in the respective Resources object, rather than to
coordinate via static objects. The `Resources` structures in this PR
will make it easier to add references to central coordination functions,
without having to rely on statics.
## Summary of changes
- For `Tenant`, the `broker_client` and `remote_storage` are bundled
into `TenantSharedResources`
- For `Timeline`, the `remote_client` is wrapped into
`TimelineResources`.
Both of these structures will get an additional deletion queue member in
#4960.
## Problem
IndexPart contains two redundant lists of layer names: a set of the
names, and then a map of name to metadata.
We already required that all the layers in `timeline_layers` are also in
`layers_metadata`, in `initialize_with_current_remote_index_part`, so if
there were any index_part.json files in the field that relied on these
sets being different, they would already be broken.
## Summary of changes
`timeline_layers` is made private and no longer read at runtime. It is
still serialized, but not deserialized.
`disk_consistent_lsn` is also made private, as this field only exists
for convenience of humans reading the serialized JSON.
This prepares us to entirely remove `timeline_layers` in a future
release, once this change is fully deployed, and therefore no
pageservers are trying to read the field.
I made a mistake when I adding `env.initial_timeline:
Optional[TimelineId]` in the #3839, should had just generated it and
used it to create a specific timeline. This PR fixes those mistakes, and
some extra calling into psql which must be slower than python field
access.
I'm still a bit nervous about attach -> crash case. But it should work.
(unlike case with timeline). Ideally would be cool to cover this with
test.
This continues tradition of adding bool flags for Tenant::set_stopping.
Probably lifecycle project will help with fixing it.
## Problem
Before, DeltaLayer dumping (via `cargo run --release -p pagectl --
print-layer-file` ) would crash as one can't call `Handle::block_on` in
an async executor thread.
## Summary of changes
Avoid the problem by using `DeltaLayerInner::load_keys` to load the keys
into RAM (which we already do during compaction), and then load the
values one by one during dumping.
- move them to pageserver which is the only dependant on the crate fail
- "move" the exported macro to the new module
- support at init time the same failpoints as runtime
Found while debugging test failures and making tests more repeatable by
allowing "exit" from pageserver start via environment variables. Made
those changes to `test_gc_cutoff.py`.
---------
Co-authored-by: Christian Schwarz <christian@neon.tech>
A very slight change that allows us to configure the UID of the
neon-postgres cgroup owner. We start postgres in this cgroup so we can
scale it with the cgroups v2 api. Currently, the control plane
overwrites the entrypoint set by `vm-builder`, so `compute_ctl` (and
thus postgres), is not started in the neon-postgres cgroup. Having
`compute_ctl` start postgres in the cgroup should fix this. However, at
the moment appears like it does not have the correct permissions.
Configuring the neon-postgres UID to `postgres` (which is the UID
`compute_ctl` runs under) should hopefully fix this.
See #4920 - the PR to modify `compute_ctl` to start postgres in the
cgorup.
See: neondatabase/autoscaling#480, neondatabase/autoscaling#477. Both
these PR's are part of an effort to increase `vm-builder`'s
configurability and allow us to adjust it as we integrate in the
monitor.
(This PR is the successor of https://github.com/neondatabase/neon/pull/4984 )
## Summary
The current way in which `EphemeralFile` uses `PageCache` complicates
the Pageserver code base to a degree that isn't worth it.
This PR refactors how we cache `EphemeralFile` contents, by exploiting
the append-only nature of `EphemeralFile`.
The result is that `PageCache` only holds `ImmutableFilePage` and
`MaterializedPage`.
These types of pages are read-only and evictable without write-back.
This allows us to remove the writeback code from `PageCache`, also
eliminating an entire failure mode.
Futher, many great open-source libraries exist to solve the problem of a
read-only cache,
much better than our `page_cache.rs` (e.g., better replacement policy,
less global locking).
With this PR, we can now explore using them.
## Problem & Analysis
Before this PR, `PageCache` had three types of pages:
* `ImmutableFilePage`: caches Delta / Image layer file contents
* `MaterializedPage`: caches results of Timeline::get (page
materialization)
* `EphemeralPage`: caches `EphemeralFile` contents
`EphemeralPage` is quite different from `ImmutableFilePage` and
`MaterializedPage`:
* Immutable and materialized pages are for the acceleration of (future)
reads of the same data using `PAGE_CACHE_SIZE * PAGE_SIZE` bytes of
DRAM.
* Ephemeral pages are a write-back cache of `EphemeralFile` contents,
i.e., if there is pressure in the page cache, we spill `EphemeralFile`
contents to disk.
`EphemeralFile` is only used by `InMemoryLayer`, for the following
purposes:
* **write**: when filling up the `InMemoryLayer`, via `impl BlobWriter
for EphemeralFile`
* **read**: when doing **page reconstruction** for a page@lsn that isn't
written to disk
* **read**: when writing L0 layer files, we re-read the `InMemoryLayer`
and put the contents into the L0 delta writer
(**`create_delta_layer`**). This happens every 10min or when
InMemoryLayer reaches 256MB in size.
The access patterns of the `InMemoryLayer` use case are as follows:
* **write**: via `BlobWriter`, strictly append-only
* **read for page reconstruction**: via `BlobReader`, random
* **read for `create_delta_layer`**: via `BlobReader`, dependent on
data, but generally random. Why?
* in classical LSM terms, this function is what writes the
memory-resident `C0` tree into the disk-resident `C1` tree
* in our system, though, the values of InMemoryLayer are stored in an
EphemeralFile, and hence they are not guaranteed to be memory-resident
* the function reads `Value`s in `Key, LSN` order, which is `!=` insert
order
What do these `EphemeralFile`-level access patterns mean for the page
cache?
* **write**:
* the common case is that `Value` is a WAL record, and if it isn't a
full-page-image WAL record, then it's smaller than `PAGE_SIZE`
* So, the `EphemeralPage` pages act as a buffer for these `< PAGE_CACHE`
sized writes.
* If there's no page cache eviction between subsequent
`InMemoryLayer::put_value` calls, the `EphemeralPage` is still resident,
so the page cache avoids doing a `write` system call.
* In practice, a busy page server will have page cache evictions because
we only configure 64MB of page cache size.
* **reads for page reconstruction**: read acceleration, just as for the
other page types.
* **reads for `create_delta_layer`**:
* The `Value` reads happen through a `BlockCursor`, which optimizes the
case of repeated reads from the same page.
* So, the best case is that subsequent values are located on the same
page; hence `BlockCursor`s buffer is maximally effective.
* The worst case is that each `Value` is on a different page; hence the
`BlockCursor`'s 1-page-sized buffer is ineffective.
* The best case translates into `256MB/PAGE_SIZE` page cache accesses,
one per page.
* the worst case translates into `#Values` page cache accesses
* again, the page cache accesses must be assumed to be random because
the `Value`s aren't accessed in insertion order but `Key, LSN` order.
## Summary of changes
Preliminaries for this PR were:
- #5003
- #5004
- #5005
- uncommitted microbenchmark in #5011
Based on the observations outlined above, this PR makes the following
changes:
* Rip out `EphemeralPage` from `page_cache.rs`
* Move the `block_io::FileId` to `page_cache::FileId`
* Add a `PAGE_SIZE`d buffer to the `EphemeralPage` struct.
It's called `mutable_tail`.
* Change `write_blob` to use `mutable_tail` for the write buffering
instead of a page cache page.
* if `mutable_tail` is full, it writes it out to disk, zeroes it out,
and re-uses it.
* There is explicitly no double-buffering, so that memory allocation per
`EphemeralFile` instance is fixed.
* Change `read_blob` to return different `BlockLease` variants depending
on `blknum`
* for the `blknum` that corresponds to the `mutable_tail`, return a ref
to it
* Rust borrowing rules prevent `write_blob` calls while refs are
outstanding.
* for all non-tail blocks, return a page-cached `ImmutablePage`
* It is safe to page-cache these as ImmutablePage because EphemeralFile
is append-only.
## Performance
How doe the changes above affect performance?
M claim is: not significantly.
* **write path**:
* before this PR, the `EphemeralFile::write_blob` didn't issue its own
`write` system calls.
* If there were enough free pages, it didn't issue *any* `write` system
calls.
* If it had to evict other `EphemeralPage`s to get pages a page for its
writes (`get_buf_for_write`), the page cache code would implicitly issue
the writeback of victim pages as needed.
* With this PR, `EphemeralFile::write_blob` *always* issues *all* of its
*own* `write` system calls.
* Also, the writes are explicit instead of implicit through page cache
write back, which will help #4743
* The perf impact of always doing the writes is the CPU overhead and
syscall latency.
* Before this PR, we might have never issued them if there were enough
free pages.
* We don't issue `fsync` and can expect the writes to only hit the
kernel page cache.
* There is also an advantage in issuing the writes directly: the perf
impact is paid by the tenant that caused the writes, instead of whatever
tenant evicts the `EphemeralPage`.
* **reads for page reconstruction**: no impact.
* The `write_blob` function pre-warms the page cache when it writes the
`mutable_tail` to disk.
* So, the behavior is the same as with the EphemeralPages before this
PR.
* **reads for `create_delta_layer`**: no impact.
* Same argument as for page reconstruction.
* Note for the future:
* going through the page cache likely causes read amplification here.
Why?
* Due to the `Key,Lsn`-ordered access pattern, we don't read all the
values in the page before moving to the next page. In the worst case, we
might read the same page multiple times to read different `Values` from
it.
* So, it might be better to bypass the page cache here.
* Idea drafts:
* bypass PS page cache + prefetch pipeline + iovec-based IO
* bypass PS page cache + use `copy_file_range` to copy from ephemeral
file into the L0 delta file, without going through user space
## Problem
The performance benchmark in `test_runner/performance/test_layer_map.py`
is currently failing due to the warning added in #4888.
## Summary of changes
The test mentioned has a `compaction_target_size` of 8192, which is just
one page size. This is an unattainable goal, as we generate at least
three pages: one for the header, one for the b-tree (minimally sized
ones have just the root node in a single page), one for the data.
Therefore, we add two pages to the warning limit. The warning text
becomes a bit less accurate but I think this is okay.
## Problem
Errors and notices that happen during a pooled connection lifecycle have
no session identifiers
## Summary of changes
Using a watch channel, we set the session ID whenever it changes. This
way we can see the status of a connection for that session
Also, adding a connection id to be able to search the entire connection
lifecycle
I will have to change these as I change remote_timeline_client api in
#4938. So a bit of cleanup, handle my comments which were just resolved
during initial review.
Cleanup:
- use unwrap in tests instead of mixed `?` and `unwrap`
- use `Handle` instead of `&'static Reactor` to make the
RemoteTimelineClient more natural
- use arrays in tests
- use plain `#[tokio::test]`
## Problem
A customer is having trouble connecting to neon from their production
environment. The logs show a mix of "Internal error" and "authentication
protocol violation" but not the full error
## Summary of changes
Make sure we don't miss any logs during SASL/SCRAM
Rather temporary solution before proper:
https://github.com/neondatabase/neon/issues/5006
It requires more plumbing so lets not attach deleted tenants first and
then implement resume.
Additionally fix `assert_prefix_empty`. It had a buggy prefix calculation,
and since we always asserted for absence of stuff it worked. Here I
started to assert for presence of stuff too and it failed. Added more
"presence" asserts to other places to be confident that it works.
Resolves [#5016](https://github.com/neondatabase/neon/issues/5016)
## Problem
The previous version of neon (that we use in the forward compatibility test)
has installed `amcheck` extension now. We can run `pg_amcheck`
unconditionally.
## Summary of changes
- Run `pg_amcheck` in compatibility tests unconditionally
Before this patch, we had the `off` and `blknum` as function-wide
mutable state. Now it's contained in the `Writer` struct.
The use of `push_bytes` instead of index-based filling of the buffer
also makes it easier to reason about what's going on.
This is prep for https://github.com/neondatabase/neon/pull/4994
Don't download ext_index.json from s3, but instead receive it as a part of spec from control plane.
This eliminates s3 access for most compute starts,
and also allows us to update extensions spec on the fly
Restores #4937 work relating to the ability to use `ResidentDeltaLayer`
(which is an Arc wrapper) in #4938 for the ValueRef's by removing the
borrow from `ValueRef` and providing it from an upper layer.
This should not have any functional changes, most importantly, the
`main` will continue to use the borrowed `DeltaLayerInner`. It might be
that I can change #4938 to be like this. If that is so, I'll gladly rip
out the `Ref` and move the borrow back. But I'll first want to look at
the current test failures.
This makes it more explicit that these are different u64-sized
namespaces.
Re-using one in place of the other would be catastrophic.
Prep for https://github.com/neondatabase/neon/pull/4994
which will eliminate the ephemeral_file::FileId and move the
blob_io::FileId into page_cache.
It makes sense to have this preliminary commit though,
to minimize amount of new concept in #4994 and other
preliminaries that depend on that work.
## Problem
As documented, the global connection pool will be high contention.
## Summary of changes
Use DashMap rather than Mutex<HashMap>.
Of note, DashMap currently uses a RwLock internally, but it's partially
sharded to reduce contention by a factor of N. We could potentially use
flurry which is a port of Java's concurrent hashmap, but I have no good
understanding of it's performance characteristics. Dashmap is at least
equivalent to hashmap but less contention.
See the read heavy benchmark to analyse our expected performance
<https://github.com/xacrimon/conc-map-bench#ready-heavy>
I also spoke with the developer of dashmap recently, and they are
working on porting the implementation to use concurrent HAMT FWIW
## Problem
PR #4839 has already reduced the number of b-tree traversals and vec
creations from 3 to 2, but as pointed out in
https://github.com/neondatabase/neon/pull/4839#discussion_r1279167815 ,
we would ideally just traverse the b-tree once during compaction.
Afer #4836, the two vecs created are one for the list of keys, lsns and
sizes, and one for the list of `(key, lsn, value reference)`. However,
they are not equal, as pointed out in
https://github.com/neondatabase/neon/pull/4839#issuecomment-1660418012
and the following comment: the key vec creation combines multiple
entries for which the lsn is changing but the key stays the same into
one, with the size being the sum of the sub-sizes. In SQL, this would
correspond to something like `SELECT key, lsn, SUM(size) FROM b_tree
GROUP BY key;` and `SELECT key, lsn, val_ref FROM b_tree;`. Therefore,
the join operation is non-trivial.
## Summary of changes
This PR merges the two lists of keys and value references into one. It's
not a trivial change and affects the size pattern of the resulting
files, which is why this is in a separate PR from #4839 .
The key vec is used in compaction for determining when to start a new
layer file. The loop uses various thresholds to come to this conclusion,
but the grouping via the key has led to the behaviour that regardless of
the threshold, it only starts a new file when either a new key is
encountered, or a new delta file.
The new code now does the combination after the merging and sorting of
the various keys from the delta files. This *mostly* does the same as
the old code, except for a detail: with the grouping done on a
per-delta-layer basis, the sorted and merged vec would still have
multiple entries for multiple delta files, but now, we don't have an
easy way to tell when a new input delta layer file is encountered, so we
cannot create multiple entries on that basis easily.
To prevent possibly infinite growth, our new grouping code compares the
combined size with the threshold, and if it is exceeded, it cuts a new
entry so that the downstream code can cut a new output file. Here, we
perform a tradeoff however, as if the threshold is too small, we risk
putting entries for the same key into multiple layer files, but if the
threshold is too big, we can in some instances exceed the target size.
Currently, we set the threshold to the target size, so in theory we
would stay below or roughly at double the `target_file_size`.
We also fix the way the size was calculated for the last key. The calculation
was wrong and accounted for the old layer's btree, even though we
already account for the overhead of the in-construction btree.
Builds on top of #4839 .
Previously list_prefixes was incorrectly used for that purpose. Change
to use list_files. Add a test.
Some drive by refactorings on python side to move helpers out of
specific test file to be widely accessible
resolves https://github.com/neondatabase/neon/issues/4499
For `delete_objects` it was injecting failures for whole delete_objects operation
and then for every delete it contains. Make it fail once for the whole operation.
## Problem
This was set to 5 seconds, which was very close to how long a compaction
took on my workstation, and when deletion is blocked on compaction the
test would fail.
We will fix this to make compactions drop out on deletion, but for the
moment let's stabilize the test.
## Summary of changes
Change timeout on timeline deletion in
`test_timeline_deletion_with_files_stuck_in_upload_queue` from 5 seconds
to 30 seconds.
To this end add
1) -e option to 'neon_local safekeeper start' command appending extra options
to safekeeper invocation;
2) Allow multiple occurrences of the same option in safekeepers, the last
value is taken.
3) Allow to specify empty string for *-auth-public-key-path opts, it
disables auth for the service.
The same option enables auth and specifies public key, so this allows to use
different public keys as well. The motivation is to
1) Allow to e.g. change pageserver key/token without replacing all compute
tokens.
2) Enable auth gradually.
## Problem
Deletions can be possibly reordered. Use fsync to avoid the case when
mark file doesnt exist but other tenant/timeline files do.
See added comments.
resolves#4987
## Problem
While adding new test results format, I've also changed the way we
upload Allure reports to S3
(722c7956bb)
to avoid duplicated results from previous runs. But it broke links at
earlier results (results are still available but on different URLs).
This PR fixes this (by reverting logic in
722c7956bb
changes), and moves the logic for storing test results into db to allure
generate step. It allows us to avoid test results duplicates in the db
and saves some time on extra s3 downloads that happened in a different
job before the PR.
Ref https://neondb.slack.com/archives/C059ZC138NR/p1691669522160229
## Summary of changes
- Move test results storing logic from a workflow to
`actions/allure-report-generate`
## Problem
HTTP batch queries currently allow us to set the isolation level and
read only, but not deferrable.
## Summary of changes
Add support for deferrable.
Echo deferrable status in response headers only if true.
Likewise, now echo read-only status in response headers only if true.
#4942 left old metrics in place for migration purposes. It was noticed
that from new metrics the total number of deleted objects was forgotten,
add it.
While reviewing, it was noticed that the delete_object could just be
delete_objects of one.
---------
Co-authored-by: Arpad Müller <arpad-m@users.noreply.github.com>
## Problem
The `BlockReader` trait is not ready to be asyncified, as associated
types are not supported by asyncification strategies like via the
`async_trait` macro, or via adopting enums.
## Summary of changes
Remove the `BlockLease` associated type from the `BlockReader` trait and
turn it into an enum instead, bearing the same name. The enum has two
variants, one of which is gated by `#[cfg(test)]`. Therefore, outside of
test settings, the enum has zero overhead over just having the
`PageReadGuard`. Using the enum allows us to impl `BlockReader` without
needing the page cache.
Part of https://github.com/neondatabase/neon/issues/4743
## Problem
The `BlockCursor::read_blob` and `BlockCursor::read_blob_into_buf`
functions are calling `read_blk` internally, so if we want to make that
function async fn, they need to be async themselves.
## Summary of changes
* We first turn `ValueRef::load` into an async fn.
* Then, we switch the `RwLock` implementation in `InMemoryLayer` to use
the one from `tokio`.
* Last, we convert the `read_blob` and `read_blob_into_buf` functions
into async fn.
In three instances we use `Handle::block_on`:
* one use is in compaction code, which currently isn't async. We put the
entire loop into an `async` block to prevent the potentially hot loop
from doing cross-thread operations.
* one use is in dumping code for `DeltaLayer`. The "proper" way to
address this would be to enable the visit function to take async
closures, but then we'd need to be generic over async fs non async,
which [isn't supported by rust right
now](https://blog.rust-lang.org/inside-rust/2022/07/27/keyword-generics.html).
The other alternative would be to do a first pass where we cache the
data into memory, and only then to dump it.
* the third use is in writing code, inside a loop that copies from one
file to another. It is is synchronous and we'd like to keep it that way
(for now?).
Part of #4743
## Problem
It's nice if `single query : single response :: batch query : batch
response`.
But at present, in the single case we send `{ query: '', params: [] }`
and get back a single `{ rows: [], ... }` object, while in the batch
case we send an array of `{ query: '', params: [] }` objects and get
back not an array of `{ rows: [], ... }` objects but a `{ results: [ {
rows: [] , ... }, { rows: [] , ... }, ... ] }` object instead.
## Summary of changes
With this change, the batch query body becomes `{ queries: [{ query: '',
params: [] }, ... ] }`, which restores a consistent relationship between
the request and response bodies.
Originated from test failure where we got SlowDown error from s3.
The patch generalizes `download_retry` to not be download specific.
Resulting `retry` function is moved to utils crate. `download_retries`
is now a thin wrapper around this `retry` function.
To ensure that all needed retries are in place test code now uses
`test_remote_failures=1` setting.
Ref https://neondb.slack.com/archives/C059ZC138NR/p1691743624353009
## Problem
Currently, image generation reads delta layers before writing out
subsequent image layers, which updates the access time of the delta
layers and effectively puts them at the back of the queue for eviction.
This is the opposite of what we want, because after a delta layer is
covered by a later image layer, it's likely that subsequent reads of
latest data will hit the image rather than the delta layer, so the delta
layer should be quite a good candidate for eviction.
## Summary of changes
`RequestContext` gets a new `ATimeBehavior` field, and a
`RequestContextBuilder` helper so that we can optionally add the new
field without growing `RequestContext::new` every time we add something
like this.
Request context is passed into the `record_access` function, and the
access time is not updated if `ATimeBehavior::Skip` is set.
The compaction background task constructs its request context with this
skip policy.
Closes: https://github.com/neondatabase/neon/issues/4969
This code was mostly copied from walsender.c and the idea was to keep it
similar to walsender.c, so that we can easily copy-paste future upstream
changes to walsender.c to waproposer_utils.c, too. But right now I see that
deleting it doesn't break anything, so it's better to remove unused parts.
It allows term leader to ensure he pulls data from the correct term. Absense of
it wasn't very problematic due to CRC checks, but let's be strict.
walproposer still doesn't use it as we're going to remove recovery completely
from it.
Patches a bug in vm-builder where it did not include enough parameters
in the query string. These parameters are `host=localhost port=5432`.
These parameters were not necessary for the monitor because the `pq` go
postgres driver included them by default.
## Problem
In some places, the lock on `InMemoryLayerInner` is only created to
obtain `end_lsn`. This is not needed however, if we move `end_lsn` to
`InMemoryLayer` instead.
## Summary of changes
Make `end_lsn` a member of `InMemoryLayer`, and do less locking of
`InMemoryLayerInner`. `end_lsn` is changed from `Option<Lsn>` into an
`OnceLock<Lsn>`. Thanks to this change, we don't need to lock any more
in three functions.
Part of #4743 . Suggested in
https://github.com/neondatabase/neon/pull/4905#issuecomment-1666458428 .
Found this log on staging:
```
2023-08-10T17:42:58.573790Z INFO handling interactive connection from client protocol="ws"
```
We seem to be losing websocket span in spawn, this patch fixes it.
## Problem
1MB response limit is very small.
## Summary of changes
This data is not yet tracked, so we shoudn't raise the limit too high yet.
But as discussed with @kelvich and @conradludgate, this PR lifts it to
10MB, and adds also details of the limit to the error response.
`pg_regress` is flaky: https://github.com/neondatabase/neon/issues/559
Consolidated `CHECKPOINT` to `check_restored_datadir_content`, add a
wait for `wait_for_last_flush_lsn`.
Some recently introduced flakyness was fixed with #4948.
---------
Co-authored-by: Joonas Koivunen <joonas@neon.tech>
## Problem
The `DiskBtreeReader::visit` function calls `read_blk` internally, and
while #4863 converted the API of `visit` to async, the internal function
is still recursive. So, analogously to #4838, we turn the recursive
function into an iterative one.
## Summary of changes
First, we prepare the change by moving the for loop outside of the case
switch, so that we only have one loop that calls recursion. Then, we
switch from using recursion to an approach where we store the search
path inside the tree on a stack on the heap.
The caller of the `visit` function can control when the search over the
B-Tree ends, by returning `false` from the closure. This is often used
to either only find one specific entry (by always returning `false`),
but it is also used to iterate over all entries of the B-tree (by always
returning `true`), or to look for ranges (mostly in tests, but
`get_value_reconstruct_data` also has such a use).
Each stack entry contains two things: the block number (aka the block's
offset), and a children iterator. The children iterator is constructed
depending on the search direction, and with the results of a binary
search over node's children list. It is the only thing that survives a
spilling/push to the stack, everything else is reconstructed. In other
words, each stack spill, will, if the search is still ongoing, cause an
entire re-parsing of the node. Theoretically, this would be a linear
overhead in the number of leaves the search visits. However, one needs
to note:
* the workloads to look for a specific entry are just visiting one leaf,
ever, so this is mostly about workloads that visit larger ranges,
including ones that visit the entire B-tree.
* the requests first hit the page cache, so often the cost is just in
terms of node deserialization
* for nodes that only have leaf nodes as children, no spilling to the
stack-on-heap happens (outside of the initial request where the iterator
is `None`). In other words, for balanced trees, the spilling overhead is
$\Theta\left(\frac{n}{b^2}\right)$, where `b` is the branching factor
and `n` is the number of nodes in the tree. The B-Trees in the current
implementation have a branching factor of roughly `PAGE_SZ/L` where
`PAGE_SZ` is 8192, and `L` is `DELTA_KEY_SIZE = 26` or `KEY_SIZE = 18`
in production code, so this gives us an estimate that we'd be re-loading
an inner node for every 99000 leaves in the B-tree in the worst case.
Due to these points above, I'd say that not fully caching the inner
nodes with inner children is reasonable, especially as we also want to
be fast for the "find one specific entry" workloads, where the stack
content is never accessed: any action to make the spilling
computationally more complex would contribute to wasted cycles here,
even if these workloads "only" spill one node for each depth level of
the b-tree (which is practically always a low single-digit number,
Kleppmann points out on page 81 that for branching factor 500, a four
level B-tree with 4 KB pages can store 250 TB of data).
But disclaimer, this is all stuff I thought about in my head, I have not
confirmed it with any benchmarks or data.
Builds on top of #4863, part of #4743
The test mutates a shared directory which does not work with multiple
concurrent tests. It is being fixed, so this should be a very temporary
band-aid.
Cc: #4949.
## Problem
For some tests, we override the default timeout (300s / 5m) with a larger
values like 600s / 10m or even 1800s / 30m, even if it's not required.
I've collected some statistics (for the last 60 days) for tests
duration:
| test | max (s) | p99 (s) | p50 (s) | count |
|-----------------------------------|---------|---------|---------|-------|
| test_hot_standby | 9 | 2 | 2 | 5319 |
| test_import_from_vanilla | 16 | 9 | 6 | 5692 |
| test_import_from_pageserver_small | 37 | 7 | 5 | 5719 |
| test_pg_regress | 101 | 73 | 44 | 5642 |
| test_isolation | 65 | 56 | 39 | 5692 |
A couple of tests that I left with custom 600s / 10m timeout.
| test | max (s) | p99 (s) | p50 (s) | count |
|-----------------------------------|---------|---------|---------|-------|
| test_gc_cutoff | 456 | 224 | 109 | 5694 |
| test_pageserver_chaos | 528 | 267 | 121 | 5712 |
## Summary of changes
- Remove `@pytest.mark.timeout` annotation from several tests
Don't panic if library or extension is not found in remote extension storage
or download has failed. Instead, log the error and proceed - if file is not
present locally as well, postgres will fail with postgres error. If it is a
shared_preload_library, it won't start, because of bad config. Otherwise, it
will just fail to run the SQL function/ command that needs the library.
Also, don't try to download extensions if remote storage is not configured.
In the quest to solve #4745 by moving the download/evictedness to be
internally mutable factor of a Layer and get rid of `trait
PersistentLayer` at least for prod usage, `layer_removal_cs`, we present
some misc cleanups.
---------
Co-authored-by: Dmitry Rodionov <dmitry@neon.tech>
## Problem
When an endpoint is shutting down, it can take a few seconds. Currently
when starting a new compute, this causes an "endpoint is in transition"
error. We need to add delays before retrying to ensure that we allow
time for the endpoint to shutdown properly.
## Summary of changes
Adds a delay before retrying in auth. connect_to_compute already has
this delay
## Problem
One might wonder why the code here doesn't use `TimelineId` or
`TenantId`. I originally had a refactor to use them, but then discarded
it, because converting to strings on each time there is a read or write
is wasteful.
## Summary of changes
We add some docs explaining why here no `TimelineId` or `TenantId` is
being used.
## Problem
The current test history format is a bit inconvenient:
- It stores all test results in one row, so all queries should include
subqueries which expand the test
- It includes duplicated test results if the rerun is triggered manually
for one of the test jobs (for example, if we rerun `debug-pg14`, then
the report will include duplicates for other build types/postgres
versions)
- It doesn't have a reference to run_id, which we use to create a link
to allure report
Here's the proposed new format:
```
id BIGSERIAL PRIMARY KEY,
parent_suite TEXT NOT NULL,
suite TEXT NOT NULL,
name TEXT NOT NULL,
status TEXT NOT NULL,
started_at TIMESTAMPTZ NOT NULL,
stopped_at TIMESTAMPTZ NOT NULL,
duration INT NOT NULL,
flaky BOOLEAN NOT NULL,
build_type TEXT NOT NULL,
pg_version INT NOT NULL,
run_id BIGINT NOT NULL,
run_attempt INT NOT NULL,
reference TEXT NOT NULL,
revision CHAR(40) NOT NULL,
raw JSONB COMPRESSION lz4 NOT NULL,
```
## Summary of changes
- Misc allure changes:
- Update allure to 2.23.1
- Delete files from previous runs in HTML report (by using `sync
--delete` instead of `mv`)
- Use `test-cases/*.json` instead of `suites.json`, using this directory
allows us to catch all reruns.
- Until we migrated `scripts/flaky_tests.py` and
`scripts/benchmark_durations.py` store test results in 2 formats (in 2
different databases).
## Problem
When an endpoint is shutting down, it can take a few seconds. Currently
when starting a new compute, this causes an "endpoint is in transition"
error. We need to add delays before retrying to ensure that we allow
time for the endpoint to shutdown properly.
## Summary of changes
Adds a delay before retrying in auth. connect_to_compute already has
this delay
## Problem
The safekeeper advertises the same address specified in `--listen-pg`,
which is problematic when the listening address is different from the
address that the pageserver can use to connect to the safekeeper.
## Summary of changes
Add a new optional flag called `--advertise-pg` for the address to be
advertised. If this flag is not specified, the behavior is the same as
before.
## Problem
Currently to know how long pageserver startup took requires inspecting
logs.
## Summary of changes
`pageserver_startup_duration_ms` metric is added, with label `phase` for
different phases of startup.
These are broken down by phase, where the phases correspond to the
existing wait points in the code:
- Start of doing I/O
- When tenant load is done
- When initial size calculation is done
- When background jobs start
- Then "complete" when everything is done.
`pageserver_startup_is_loading` is a 0/1 gauge that indicates whether we are in the initial load of tenants.
`pageserver_tenant_activation_seconds` is a histogram of time in seconds taken to activate a tenant.
Co-authored-by: Joonas Koivunen <joonas@neon.tech>
## Problem
The pageserver<->safekeeper protocol uses error messages to indicate end
of stream. pageserver already logs these at INFO level, but the inner
error message includes the word "ERROR", which interferes with log
searching.
Example:
```
walreceiver connection handling ended: db error: ERROR: ending streaming to Some("pageserver") at 0/4031CA8
```
The inner DbError has a severity of ERROR so DbError's Display
implementation includes that ERROR, even though we are actually
logging the error at INFO level.
## Summary of changes
Introduce an explicit WalReceiverError type, and in its From<>
for postgres errors, apply the logic from ExpectedError, for
expected errors, and a new condition for successes.
The new output looks like:
```
walreceiver connection handling ended: Successful completion: ending streaming to Some("pageserver") at 0/154E9C0, receiver is caughtup and there is no computes
```
## Problem
I spent a few minutes seeing how fast I could get our regression test
suite to run on my workstation, for when I want to run a "did I break
anything?" smoke test before pushing to CI.
- Test runtime was dominated by a couple of tests that run for longer
than all the others take together
- Test concurrency was limited to <16 by the ports-per-worker setting
There's no "right answer" for how long a test should
be, but as a rule of thumb, no one test should run
for much longer than the time it takes to run all the
other tests together.
## Summary of changes
- Make the ports per worker setting dynamic depending on worker count
- Modify the longest running tests to run for a shorter time
(`test_duplicate_layers` which uses a pgbench runtime) or fewer
iterations (`test_restarts_frequent_checkpoints`).
## Problem
PR #4839 didn't output the keys/values in lsn order, but for a given
key, the lsns were kept in incoming file order.
I think the ordering by lsn is expected.
## Summary of changes
We now also sort by `(key, lsn)`, like we did before #4839.
## Problem
Running `pagectl draw-timeline` on a pageserver directory wasn't working
out of the box because it trips up on the `metadata` file.
## Summary of changes
Just ignore the `metadata` file in the list of input files passed to
`draw-timeline`.
Cache changes are now DEBUG2
Logs that indicate disabled caches now explicitly call out that the file cache is disabled on WARNING level instead of LOG/INFO
We currently cannot drop tenant before removing it's directory, or use
Tenant::drop for this. This creates unnecessary or inactionable warnings
during detach at least. Silence the most typical, file not found. Log
remaining at `error!`.
Cc: #2442
We don't know how our s3 remote_storage is performing, or if it's
blocking the shutdown. Well, for sampling reasons, we will not really
know even after this PR.
Add metrics:
- align remote_storage metrics towards #4813 goals
- histogram
`remote_storage_s3_request_seconds{request_type=(get_object|put_object|delete_object|list_objects),
result=(ok|err|cancelled)}`
- histogram `remote_storage_s3_wait_seconds{request_type=(same kinds)}`
- counter `remote_storage_s3_cancelled_waits_total{request_type=(same
kinds)}`
Follow-up work:
- After release, remove the old metrics, migrate dashboards
Histogram buckets are rough guesses, need to be tuned. In pageserver we
have a download timeout of 120s, so I think the 100s bucket is quite
nice.
## Problem
The current output from a prod binary at startup is:
```
git-env:765455bca22700e49c053d47f44f58a6df7c321f failpoints: true, features: [] launch_timestamp: 2023-08-02 10:30:35.545217477 UTC
```
It's confusing to read that line, then read the code and think "if
failpoints is true, but not in the features list, what does that mean?".
As far as I can tell, the check of `fail/failpoints` is just always
false because cargo doesn't expose features across crates like this: the
`fail/failpoints` syntax works in the cargo CLI but not from a macro in
some crate other than `fail`.
## Summary of changes
Remove the lines that try to check `fail/failpoints` from the pageserver
entrypoint module. This has no functional impact but makes the code
slightly easier to understand when trying to make sense of the line
printed on startup.
## Problem
Pre-requisites for #4852 and #4853
## Summary of changes
1. Includes the client's IP address (which we already log) with the span
info so we can have it on all associated logs. This makes making
dashboards based on IP addresses easier.
2. Switch to a consistent error/warning log for errors during
connection. This includes error, num_retries, retriable=true/false and a
consistent log message that we can grep for.
## Problem
The functions `DeltaLayer::load_inner` and `ImageLayer::load_inner` are
calling `read_blk` internally, which we would like to turn into an async
fn.
## Summary of changes
We switch from `once_cell`'s `OnceCell` implementation to the one in
`tokio` in order to be able to call an async `get_or_try_init` function.
Builds on top of #4839, part of #4743
During deploys of 2023-08-03 we logged too much on shutdown. Fix the
logging by timing each top level shutdown step, and possibly warn on it
taking more than a rough threshold, based on how long I think it
possibly should be taking. Also remove all shutdown logging from
background tasks since there is already "shutdown is taking a long time"
logging.
Co-authored-by: John Spray <john@neon.tech>
## Problem
`DiskBtreeReader::get` and `DiskBtreeReader::visit` both call `read_blk`
internally, which we would like to make async in the future. This PR
focuses on making the interface of these two functions `async`. There is
further work to be done in forms of making `visit` to not be recursive
any more, similar to #4838. For that, see
https://github.com/neondatabase/neon/pull/4884.
Builds on top of https://github.com/neondatabase/neon/pull/4839, part of
https://github.com/neondatabase/neon/issues/4743
## Summary of changes
Make `DiskBtreeReader::get` and `DiskBtreeReader::visit` async functions
and `await` in the places that call these functions.
## Problem
When setting up for the first time I hit a couple of nits running tests:
- It wasn't obvious that `openssl` and `poetry` were needed (poetry is
mentioned kind of obliquely via "dependency installation notes" rather
than being in the list of rpm/deb packages to install.
- It wasn't obvious how to get the tests to run for just particular
parameters (e.g. just release mode)
## Summary of changes
Add openssl and poetry to the package lists.
Add an example of how to run pytest for just a particular build type and
postgres version.
## Problem
neon_fixtures.py has grown to unmanageable size. It attracts conflicts.
When adding specific utils under for example `fixtures/pageserver`
things sometimes need to import stuff from `neon_fixtures.py` which
creates circular import. This is usually only needed for type
annotations, so `typing.TYPE_CHECKING` flag can mask the issue.
Nevertheless I believe that splitting neon_fixtures.py into smaller
parts is a better approach.
Currently the PR contains small things, but I plan to continue and move
NeonEnv to its own `fixtures.env` module. To keep the diff small I think
this PR can already be merged to cause less conflicts.
UPD: it looks like currently its not really possible to fully avoid
usage of `typing.TYPE_CHECKING`, because some components directly depend
on each other. I e Env -> Cli -> Env cycle. But its still worth it to
avoid it in as many places as possible. And decreasing neon_fixture's
size still makes sense.
## Problem
If AWS credentials are not set locally (via
AWS_ACCESS_KEY_ID/AWS_SECRET_ACCESS_KEY env vars)
`test_remote_library[release-pg15-mock_s3]` test fails with the
following error:
```
ERROR could not start the compute node: Failed to download a remote file: Failed to download S3 object: failed to construct request
```
## Summary of changes
- set AWS credentials for endpoints programmatically
## Problem
The k-merge in pageserver compaction currently relies on iterators over
the keys and also over the values. This approach does not support async
code because we are using iterators and those don't support async in
general. Also, the k-merge implementation we use doesn't support async
either. Instead, as we already load all the keys into memory, just do
sorting in-memory.
## Summary of changes
The PR can be read commit-by-commit, but most importantly, it:
* Stops using kmerge in compaction, using slice sorting instead.
* Makes `load_keys` and `load_val_refs` async, using `Handle::block_on`
in the compaction code as we don't want to turn the compaction function,
called inside `spawn_blocking`, into an async fn.
Builds on top of #4836, part of
https://github.com/neondatabase/neon/issues/4743
## Problem
Error messages like this coming up during normal operations:
```
Compaction failed, retrying in 2s: timeline is Stopping
Compaction failed, retrying in 2s: Cannot run compaction iteration on inactive tenant
```
## Summary of changes
Add explicit handling for the shutdown case in these locations, to
suppress error logs.
as needed since #4715 or this will happen:
```
ERROR panic{thread=main location=.../hyper-rustls-0.23.2/src/config.rs:48:9}: no CA certificates found
```
Add infrastructure to dynamically load postgres extensions and shared libraries from remote extension storage.
Before postgres start downloads list of available remote extensions and libraries, and also downloads 'shared_preload_libraries'. After postgres is running, 'compute_ctl' listens for HTTP requests to load files.
Postgres has new GUC 'extension_server_port' to specify port on which 'compute_ctl' listens for requests.
When PostgreSQL requests a file, 'compute_ctl' downloads it.
See more details about feature design and remote extension storage layout in docs/rfcs/024-extension-loading.md
---------
Co-authored-by: Anastasia Lubennikova <anastasia@neon.tech>
Co-authored-by: Alek Westover <alek.westover@gmail.com>
Two stabs at this, by mocking a http receiver and the globals out (now
reverted) and then by separating the timeline dependency and just
testing what kind of events certain timelines produce. I think this
pattern could work for some of our problems.
Follow-up to #4822.
## Problem
When the eviction threshold is an integer multiple of the eviction
period, it is unreliable to skip imitating accesses based on whether the
last imitation was more recent than the threshold.
This is because as finite time passes
between the time used for the periodic execution, and the 'now' time
used for updating last_layer_access_imitation. When this is just a few
milliseconds, and everything else is on-time, then a 5 second threshold
with a 1 second period will end up entering its 5th iteration slightly
_less than_ 5 second since last_layer_access_imitation, and thereby
skipping instead of running the imitation. If a few milliseconds then
pass before we check the access time of a file that _should_ have been
bumped by the imitation pass, then we end up evicting something we
shouldn't have evicted.
## Summary of changes
We can make this race far less likely by using the threshold minus one
interval as the period for re-executing the imitate_layer_accesses: that
way we're not vulnerable to racing by just a few millis, and there would
have to be a delay of the order `period` to cause us to wrongly evict a
layer.
This is not a complete solution: it would be good to revisit this and
use a non-walltime mechanism for pinning these layers into local
storage, rather than relying on bumping access times.
## Problem
The k-merge in pageserver compaction currently relies on iterators over
the keys and also over the values. This approach does not support async
code because we are using iterators and those don't support async in
general. Also, the k-merge implementation we use doesn't support async
either. Instead, as we already load all the keys into memory, the plan
is to just do the sorting in-memory for now, switch to async, and then
once we want to support workloads that don't have all keys stored in
memory, we can look into switching to a k-merge implementation that
supports async instead.
## Summary of changes
The core of this PR is the move from functions on the `PersistentLayer`
trait to return custom iterator types to inherent functions on `DeltaLayer`
that return buffers with all keys or value references.
Value references are a type we created in this PR, containing a
`BlobRef` as well as an `Arc` pointer to the `DeltaLayerInner`, so that
we can lazily load the values during compaction. This preserves the
property of the current code.
This PR does not switch us to doing the k-merge via sort on slices, but
with this PR, doing such a switch is relatively easy and only requires
changes of the compaction code itself.
Part of https://github.com/neondatabase/neon/issues/4743
commit
commit 5f8fd640bf
Author: Alek Westover <alek.westover@gmail.com>
Date: Wed Jul 26 08:24:03 2023 -0400
Upload Test Remote Extensions (#4792)
switched to using the release tag instead of `latest`, but,
the `promote-images` job only uploads `latest` to the prod ECR.
The switch to using release tag was good in principle, but,
reverting that part to make the release pipeine work.
Note that a proper fix should abandon use of `:latest` tag
at all: currently, if a `main` pipeline runs concurrently
with a `release` pipeline, the `release` pipeline may end
up using the `main` pipeline's images.
## Problem
See https://neondb.slack.com/archives/C036U0GRMRB/p1689148023067319
## Summary of changes
Define NEON_SMGR in smgr.h
## Checklist before requesting a review
- [ ] I have performed a self-review of my code.
- [ ] If it is a core feature, I have added thorough tests.
- [ ] Do we need to implement analytics? if so did you add the relevant
metrics to the dashboard?
- [ ] If this PR requires public announcement, mark it with
/release-notes label and add several sentences in this section.
## Checklist before merging
- [ ] Do not forget to reformat commit message to not include the above
checklist
---------
Co-authored-by: Konstantin Knizhnik <knizhnik@neon.tech>
We want to have timeline_written_size_delta which is defined as
difference to the previously sent `timeline_written_size` from the
current `timeline_written_size`.
Solution is to send it. On the first round `disk_consistent_lsn` is used
which is captured during `load` time. After that an incremental "event"
is sent on every collection. Incremental "events" are not part of
deduplication.
I've added some infrastructure to allow somewhat typesafe
`EventType::Absolute` and `EventType::Incremental` factories per
metrics, now that we have our first `EventType::Incremental` usage.
## Problem
Compatibility tests fail from time to time due to `pg_tenant_only_port`
port collision (added in https://github.com/neondatabase/neon/pull/4731)
## Summary of changes
- replace `pg_tenant_only_port` value in config with new port
- remove old logic, than we don't need anymore
- unify config overrides
## Problem
Wrong use of `conf.listen_pg_addr` in `error!()`.
## Summary of changes
Use `listen_pg_addr_tenant_only` instead of `conf.listen_pg_addr`.
Signed-off-by: yaoyinnan <35447132+yaoyinnan@users.noreply.github.com>
## Problem
1. In the CacheInvalid state loop, we weren't checking the
`num_retries`. If this managed to get up to `32`, the retry_after
procedure would compute 2^32 which would overflow to 0 and trigger a div
by zero
2. When fixing the above, I started working on a flow diagram for the
state machine logic and realised it was more complex than it had to be:
a. We start in a `Cached` state
b. `Cached`: call `connect_once`. After the first connect_once error, we
always move to the `CacheInvalid` state, otherwise, we return the
connection.
c. `CacheInvalid`: we attempt to `wake_compute` and we either switch to
Cached or we retry this step (or we error).
d. `Cached`: call `connect_once`. We either retry this step or we have a
connection (or we error) - After num_retries > 1 we never switch back to
`CacheInvalid`.
## Summary of changes
1. Insert a `num_retries` check in the `handle_try_wake` procedure. Also
using floats in the retry_after procedure to prevent the overflow
entirely
2. Refactor connect_to_compute to be more linear in design.
## Problem
Existing IndexPart unit tests only exercised the version 1 format (i.e.
without deleted_at set).
## Summary of changes
Add a test that sets version to 2, and sets a value for deleted_at.
Closes https://github.com/neondatabase/neon/issues/4162
## Problem
`DiskBtreeReader::dump` calls `read_blk` internally, which we want to
make async in the future. As it is currently relying on recursion, and
async doesn't like recursion, we want to find an alternative to that and
instead traverse the tree using a loop and a manual stack.
## Summary of changes
* Make `DiskBtreeReader::dump` and all the places calling it async
* Make `DiskBtreeReader::dump` non-recursive internally and use a stack
instead. It now deparses the node in each iteration, which isn't
optimal, but on the other hand it's hard to store the node as it is
referencing the buffer. Self referential data are hard in Rust. For a
dumping function, speed isn't a priority so we deparse the node multiple
times now (up to branching factor many times).
Part of https://github.com/neondatabase/neon/issues/4743
I have verified that output is unchanged by comparing the output of this
command both before and after this patch:
```
cargo test -p pageserver -- particular_data --nocapture
```
## Problem
ref https://github.com/neondatabase/neon/pull/4721, ref
https://github.com/neondatabase/neon/issues/4709
## Summary of changes
This PR adds unit tests for wake_compute.
The patch adds a new variant `Test` to auth backends. When
`wake_compute` is called, we will verify if it is the exact operation
sequence we are expecting. The operation sequence now contains 3 more
operations: `Wake`, `WakeRetry`, and `WakeFail`.
The unit tests for proxy connects are now complete and I'll continue
work on WebSocket e2e test in future PRs.
---------
Signed-off-by: Alex Chi Z <chi@neon.tech>
## Problem
See: https://neondb.slack.com/archives/C04USJQNLD6/p1689973957908869
## Summary of changes
Bump Postgres version
## Checklist before requesting a review
- [ ] I have performed a self-review of my code.
- [ ] If it is a core feature, I have added thorough tests.
- [ ] Do we need to implement analytics? if so did you add the relevant
metrics to the dashboard?
- [ ] If this PR requires public announcement, mark it with
/release-notes label and add several sentences in this section.
## Checklist before merging
- [ ] Do not forget to reformat commit message to not include the above
checklist
---------
Co-authored-by: Konstantin Knizhnik <knizhnik@neon.tech>
## Problem
We have some amount of outdated logic in test_compatibility, that we
don't need anymore.
## Summary of changes
- Remove `PR4425_ALLOWED_DIFF` and tune `dump_differs` method to accept
allowed diffs in the future (a cleanup after
https://github.com/neondatabase/neon/pull/4425)
- Remote etcd related code (a cleanup after
https://github.com/neondatabase/neon/pull/2733)
- Don't set `preserve_database_files`
Run `pg_amcheck` in forward and backward compatibility tests to catch
some data corruption.
## Summary of changes
- Add amcheck compiling to Makefile
- Add `pg_amcheck` to test_compatibility
The test was starting two endpoints on the same branch as discovered by
@petuhovskiy.
The fix is to allow passing branch-name from the python side over to
neon_local, which already accepted it.
Split from #4824, which will handle making this more misuse resistant.
error is not needed because anyhow will have the cause chain reported
anyways.
related to test_neon_cli_basics being flaky, but doesn't actually fix
any flakyness, just the obvious stray `{e}`.
## Problem
wake_compute can fail sometimes but is eligible for retries. We retry
during the main connect, but not during auth.
## Summary of changes
retry wake_compute during auth flow if there was an error talking to
control plane, or if there was a temporary error in waking the compute
node
## Problem
In https://github.com/neondatabase/neon/issues/4743 , I'm trying to make
more of the pageserver async, but in order for that to happen, I need to
be able to persist the result of `ImageLayer::load` across await points.
For that to happen, the return value needs to be `Send`.
## Summary of changes
Use `OnceLock` in the image layer instead of manually implementing it
with booleans, locks and `Option`.
Part of #4743
## Problem
The first session event we emit is after we receive the first startup
packet from the client. This means we can't detect any issues between
TCP open and handling of the first PG packet
## Summary of changes
Add some new logs for websocket upgrade and connection handling
## Problem
We've got an example of Allure reports from 2 different runners for the
same build that started to upload at the exact second, making one
overwrite another
## Summary of changes
- Use the Postgres version to distinguish artifacts (along with the
build type)
We need some real extensions in S3 to accurately test the code for
handling remote extensions.
In this PR we just upload three extensions (anon, kq_imcx and postgis), which is
enough for testing purposes for now. In addition to creating and
uploading the extension archives, we must generate a file
`ext_index.json` which specifies important metadata about the
extensions.
---------
Co-authored-by: Anastasia Lubennikova <anastasia@neon.tech>
Co-authored-by: Alexander Bayandin <alexander@neon.tech>
## Problem
We want to measure how many users are using TCP/WS connections.
We also want to measure how long it takes to establish a connection with
the compute node.
I plan to also add a separate counter for HTTP requests, but because of
pooling this needs to be disambiguated against new HTTP compute
connections
## Summary of changes
* record connection type (ws/tcp) in the connection counters.
* record connection latency including retry latency
## Problem
Currently we delete local files first, so if pageserver restarts after
local files deletion then remote deletion is not continued. This can be
solved with inversion of these steps.
But even if these steps are inverted when index_part.json is deleted
there is no way to distinguish between "this timeline is good, we just
didnt upload it to remote" and "this timeline is deleted we should
continue with removal of local state". So to solve it we use another
mark file. After index part is deleted presence of this mark file
indentifies that it was a deletion intention.
Alternative approach that was discussed was to delete all except
metadata first, and then delete metadata and index part. In this case we
still do not support local only configs making them rather unsafe
(deletion in them is already unsafe, but this direction solidifies this
direction instead of fixing it). Another downside is that if we crash
after local metadata gets removed we may leave dangling index part on
the remote which in theory shouldnt be a big deal because the file is
small.
It is not a big change to choose another approach at this point.
## Summary of changes
Timeline deletion sequence:
1. Set deleted_at in remote index part.
2. Create local mark file.
3. Delete local files except metadata (it is simpler this way, to be
able to reuse timeline initialization code that expects metadata)
4. Delete remote layers
5. Delete index part
6. Delete meta, timeline directory.
7. Delete mark file.
This works for local only configuration without remote storage.
Sequence is resumable from any point.
resolves#4453
resolves https://github.com/neondatabase/neon/pull/4552 (the issue was
created with async cancellation in mind, but we can still have issues
with retries if metadata is deleted among the first by remove_dir_all
(which doesnt have any ordering guarantees))
---------
Co-authored-by: Joonas Koivunen <joonas@neon.tech>
Co-authored-by: Christian Schwarz <christian@neon.tech>
This PR adds support for non-interactive transaction query endpoint.
It accepts an array of queries and parameters and returns an array of
query results. The queries will be run in a single transaction one
after another on the proxy side.
count only once; on startup create the counter right away because we
will not observe any changes later.
small, probably never reachable from outside fix for #4796.
We currently have a timeseries for each of the tenants in different
states. We only want this for Broken. Other states could be counters.
Fix this by making the `pageserver_tenant_states_count` a counter
without a `tenant_id` and
add a `pageserver_broken_tenants_count` which has a `tenant_id` label,
each broken tenant being 1.
Given now we've refactored `connect_to_compute` as a generic, we can
test it with mock backends. In this PR, we mock the error API and
connect_once API to test the retry behavior of `connect_to_compute`. In
the next PR, I'll add mock for credentials so that we can also test
behavior with `wake_compute`.
ref https://github.com/neondatabase/neon/issues/4709
---------
Signed-off-by: Alex Chi Z <chi@neon.tech>
In #4743, we'd like to convert the read path to use `async` rust. In
preparation of that, this PR switches some functions that are calling
lower level functions like `BlockReader::read_blk`,
`BlockCursor::read_blob`, etc into `async`. The PR does not switch all
functions however, and only focuses on the ones which are easy to
switch.
This leaves around some async functions that are (currently)
unnecessarily `async`, but on the other hand it makes future changes
smaller in diff.
Part of #4743 (but does not completely address it).
Fix mx_offset_to_flags_offset() function
Fixes issue #4774
Postgres `MXOffsetToFlagsOffset` was not correctly converted to Rust
because cast to u16 is done before division by modulo. It is possible
only if divider is power of two.
Add a small rust unit test to check that the function produces same results
as the PostgreSQL macro, and extend the existing python test to cover
this bug.
Co-authored-by: Konstantin Knizhnik <knizhnik@neon.tech>
Co-authored-by: Heikki Linnakangas <heikki@neon.tech>
## Problem
close https://github.com/neondatabase/neon/issues/4712
## Summary of changes
Previously, when flushing frozen layers, it was split into two
operations: add delta layer to disk + remove frozen layer from memory.
This would cause a short period of time where we will have the same data
both in frozen and delta layer. In this PR, we merge them into one
atomic operation in layer map manager, therefore simplifying the code.
Note that if we decide to create image layers for L0 flush, it will
still be split into two operations on layer map.
---------
Signed-off-by: Alex Chi Z <chi@neon.tech>
Co-authored-by: Joonas Koivunen <joonas@neon.tech>
As seen in staging logs with some massive compactions
(create_image_layer), in addition to racing with compaction or gc or
even between two invocations to `evict_layer_batch`.
Cc: #4745Fixes: #3851 (organic tech debt reduction)
Solution is not to log the Not Found in such cases; it is perfectly
natural to happen. Route to this is quite long, but implemented two
cases of "race between two eviction processes" which are like our disk
usage based eviction and eviction_task, both have the separate "lets
figure out what to evict" and "lets evict" phases.
Removes a bunch of cases which used `tokio::select` to emulate the
`tokio::time::timeout` function. I've done an additional review on the
cancellation safety of these futures, all of them seem to be
cancellation safe (not that `select!` allows non-cancellation-safe
futures, but as we touch them, such a review makes sense).
Furthermore, I correct a few mentions of a non-existent
`tokio::timeout!` macro in the docs to the `tokio::time::timeout`
function.
Adds in a barrier for the duration of the `Tenant::shutdown`.
`pageserver_shutdown` will join this await, `detach`es and `ignore`s
will not.
Fixes#4429.
---------
Co-authored-by: Christian Schwarz <christian@neon.tech>
Updated the description that appears for hnsw when you query extensions:
```
neondb=> SELECT * FROM pg_available_extensions WHERE name = 'hnsw';
name | default_version | installed_version | comment
----------------------+-----------------+-------------------+--------------------------------------------------
hnsw | 0.1.0 | | ** Deprecated ** Please use pg_embedding instead
(1 row)
```
---------
Co-authored-by: Alexander Bayandin <alexander@neon.tech>
## Problem
We're going to reset S3 buckets for extensions
(https://github.com/neondatabase/aws/pull/413), and as soon as we're
going to change the format we store extensions on S3. Let's stop
uploading extensions in the old format.
## Summary of changes
- Disable `aws s3 cp` step for extensions
Compute now uses special safekeeper WAL service port allowing auth tokens with
only tenant scope. Adds understanding of this port to neon_local and fixtures,
as well as test of both ports behaviour with different tokens.
ref https://github.com/neondatabase/neon/issues/4730
## Problem
We use a patched version of `sharded-slab` with increased MAX_THREADS
[1]. It is not required anymore because safekeepers are async now.
A valid comment from the original PR tho [1]:
> Note that patch can affect other rust services, not only the
safekeeper binary.
- [1] https://github.com/neondatabase/neon/pull/4122
## Summary of changes
- Remove patch for `sharded-slab`
## Problem
Second half of #4699. we were maintaining 2 implementations of
handle_client.
## Summary of changes
Merge the handle_client code, but abstract some of the details.
## Checklist before requesting a review
- [X] I have performed a self-review of my code.
- [ ] If it is a core feature, I have added thorough tests.
- [ ] Do we need to implement analytics? if so did you add the relevant
metrics to the dashboard?
- [ ] If this PR requires public announcement, mark it with
/release-notes label and add several sentences in this section.
## Checklist before merging
- [ ] Do not forget to reformat commit message to not include the above
checklist
## Problem
Benchmarks run takes about an hour on main branch (in a single job),
which delays pipeline results. And it takes another hour if we want to
restart the job due to some failures.
## Summary of changes
- Use `pytest-split` plugin to run benchmarks on separate CI runners in
4 parallel jobs
- Add `scripts/benchmark_durations.py` for getting benchmark durations
from the database to help `pytest-split` schedule tests more evenly. It
uses p99 for the last 10 days' results (durations).
The current distribution could be better; each worker's durations vary
from 9m to 35m, but this could be improved in consequent PRs.
## Problem
10 retries * 10 second timeouts makes for a very long retry window.
## Summary of changes
Adds a 2s timeout to sql_over_http connections, and also reduces the 10s
timeout in TCP.
## Problem
Half of #4699.
TCP/WS have one implementation of `connect_to_compute`, HTTP has another
implementation of `connect_to_compute`.
Having both is annoying to deal with.
## Summary of changes
Creates a set of traits `ConnectMechanism` and `ShouldError` that allows
the `connect_to_compute` to be generic over raw TCP stream or
tokio_postgres based connections.
I'm not super happy with this. I think it would be nice to
remove tokio_postgres entirely but that will need a lot more thought to
be put into it.
I have also slightly refactored the caching to use fewer references.
Instead using ownership to ensure the state of retrying is encoded in
the type system.
## Problem
Compactions might generate files of exactly the same name as before
compaction due to our naming of layer files. This could have already
caused some mess in the system, and is known to cause some issues like
https://github.com/neondatabase/neon/issues/4088. Therefore, we now
consider duplicated layers in the post-compaction process to avoid
violating the layer map duplicate checks.
related previous works: close
https://github.com/neondatabase/neon/pull/4094
error reported in: https://github.com/neondatabase/neon/issues/4690,
https://github.com/neondatabase/neon/issues/4088
## Summary of changes
If a file already exists in the layer map before the compaction, do not
modify the layer map and do not delete the file. The file on disk at
that time should be the new one overwritten by the compaction process.
This PR also adds a test case with a fail point that produces exactly
the same set of files.
This bypassing behavior is safe because the produced layer files have
the same content / are the same representation of the original file.
An alternative might be directly removing the duplicate check in the
layer map, but I feel it would be good if we can prevent that in the
first place.
---------
Signed-off-by: Alex Chi Z <chi@neon.tech>
Co-authored-by: Konstantin Knizhnik <knizhnik@garret.ru>
Co-authored-by: Heikki Linnakangas <heikki@neon.tech>
Co-authored-by: Joonas Koivunen <joonas@neon.tech>
The `CRITICAL_OPS_BUCKETS` is not useful for getting an accurate
picture of basebackup latency because all the observations
that negatively affect our SLI fall into one bucket, i.e., 100ms-1s.
Use the same buckets as control plane instead.
This should only affect the version of the vm-informant used. The only
change to the vm-informant from v0.12.1 to v0.13.1 was:
* https://github.com/neondatabase/autoscaling/pull/407
Just a typo fix; worth getting in anyways.
## Problem
CI doesn't work for external contributors (for PRs from forks), see
#2222 for more information.
I'm proposing the following:
- External PR is created
- PR is reviewed so that it doesn't contain any malicious code
- Label `approved-for-ci-run` is added to that PR (by the reviewer)
- A new workflow picks up this label and creates an internal branch from
that PR (the branch name is `ci-run/pr-*`)
- CI is run on the branch, but the results are also propagated to the
PRs check
- We can merge a PR itself if it's green; if not — repeat.
## Summary of changes
- Create `approved-for-ci-run.yml` workflow which handles
`approved-for-ci-run` label
- Trigger `build_and_test.yml` and `neon_extra_builds.yml` workflows on
`ci-run/pr-*` branches
## Problem
`cargo +nightly doc` is giving a lot of warnings: broken links, naked
URLs, etc.
## Summary of changes
* update the `proc-macro2` dependency so that it can compile on latest
Rust nightly, see https://github.com/dtolnay/proc-macro2/pull/391 and
https://github.com/dtolnay/proc-macro2/issues/398
* allow the `private_intra_doc_links` lint, as linking to something
that's private is always more useful than just mentioning it without a
link: if the link breaks in the future, at least there is a warning due
to that. Also, one might enable
[`--document-private-items`](https://doc.rust-lang.org/cargo/commands/cargo-doc.html#documentation-options)
in the future and make these links work in general.
* fix all the remaining warnings given by `cargo +nightly doc`
* make it possible to run `cargo doc` on stable Rust by updating
`opentelemetry` and associated crates to version 0.19, pulling in a fix
that previously broke `cargo doc` on stable:
https://github.com/open-telemetry/opentelemetry-rust/pull/904
* Add `cargo doc` to CI to ensure that it won't get broken in the
future.
Fixes#2557
## Future work
* Potentially, it might make sense, for development purposes, to publish
the generated rustdocs somewhere, like for example [how the rust
compiler does
it](https://doc.rust-lang.org/nightly/nightly-rustc/rustc_driver/index.html).
I will file an issue for discussion.
Handle test failures like:
```
AssertionError: assert not ['$ts WARN delete_timeline{tenant_id=X timeline_id=Y}: About to remove 1 files\n']
```
Instead of logging:
```
WARN delete_timeline{tenant_id=X timeline_id=Y}: Found 1 files not bound to index_file.json, proceeding with their deletion
WARN delete_timeline{tenant_id=X timeline_id=Y}: About to remove 1 files
```
For each one operation of timeline deletion, list all unref files with
`info!`, and then continue to delete them with the added spice of
logging the rare/never happening non-utf8 name with `warn!`.
Rationale for `info!` instead of `warn!`: this is a normal operation;
like we had mentioned in `test_import.py` -- basically whenever we
delete a timeline which is not idle.
Rationale for N * (`ìnfo!`|`warn!`): symmetry for the layer deletions;
if we could ever need those, we could also need these for layer files
which are not yet mentioned in `index_part.json`.
---------
Co-authored-by: Christian Schwarz <christian@neon.tech>
Tests cannot be ran without configuring tracing. Split from #4678.
Does not nag about the span checks when there is no subscriber
configured, because then the spans will have no links and nothing can be
checked. Sadly the `SpanTrace::status()` cannot be used for this.
`tracing` is always configured in regress testing (running with
`pageserver` binary), which should be enough.
Additionally cleans up the test code in span checks to be in the test
code. Fixes a `#[should_panic]` test which was flaky before these
changes, but the `#[should_panic]` hid the flakyness.
Rationale for need: Unit tests might not be testing only the public or
`feature="testing"` APIs which are only testable within `regress` tests
so not all spans might be configured.
## Problem
ref https://github.com/neondatabase/neon/issues/4373
## Summary of changes
A step towards immutable layer map. I decided to finish the refactor
with this new approach and apply
https://github.com/neondatabase/neon/pull/4455 on this patch later.
In this PR, we moved all modifications of the layer map to one place
with semantic operations like `initialize_local_layers`,
`finish_compact_l0`, `finish_gc_timeline`, etc, which is now part
of `LayerManager`. This makes it easier to build new features upon
this PR:
* For immutable storage state refactor, we can simply replace the layer
map with `ArcSwap<LayerMap>` and remove the `layers` lock. Moving
towards it requires us to put all layer map changes in a single place as
in https://github.com/neondatabase/neon/pull/4455.
* For manifest, we can write to manifest in each of the semantic
functions.
---------
Signed-off-by: Alex Chi Z <chi@neon.tech>
Co-authored-by: Christian Schwarz <christian@neon.tech>
If database was created with `is_template true` Postgres doesn't allow
dropping it right away and throws error
```
ERROR: cannot drop a template database
```
so we have to unset `is_template` first.
Fixing it, I noticed that our `escape_literal` isn't exactly correct
and following the same logic as in `quote_literal_internal`, we need to
prepend string with `E`. Otherwise, it's not possible to filter
`pg_database` using `escape_literal()` result if name contains `\`, for
example.
Also use `FORCE` to drop database even if there are active connections.
We run this from `cloud_admin`, so it should have enough privileges.
NB: there could be other db states, which prevent us from dropping
the database. For example, if db is used by any active subscription
or logical replication slot.
TODO: deal with it once we allow logical replication. Proper fix should
involve returning an error code to the control plane, so it could
figure out that this is a non-retryable error, return it to the user and
mark operation as permanently failed.
Related to neondatabase/cloud#4258
## Problem
In the logs, I noticed we still weren't retrying in some cases. Seemed
to be timeouts but we explicitly wanted to handle those
## Summary of changes
Retry on io::ErrorKind::TimedOut errors.
Handle IO errors in tokio_postgres::Error.
## Problem
It took me a while to understand the purpose of all the tasks spawned in
the main functions.
## Summary of changes
Utilising the type system and less macros, plus much more comments,
document the shutdown procedure of each task in detail
## Problem
If we fail to wake up the compute node, a subsequent connect attempt
will definitely fail. However, kubernetes won't fail the connection
immediately, instead it hangs until we timeout (10s).
## Summary of changes
Refactor the loop to allow fast retries of compute_wake and to skip a
connect attempt.
## Problem
#4598 compute nodes are not accessible some time after wake up due to
kubernetes DNS not being fully propagated.
## Summary of changes
Update connect retry mechanism to support handling IO errors and
sleeping for 100ms
## Checklist before requesting a review
- [x] I have performed a self-review of my code.
- [ ] If it is a core feature, I have added thorough tests.
- [ ] Do we need to implement analytics? if so did you add the relevant
metrics to the dashboard?
- [ ] If this PR requires public announcement, mark it with
/release-notes label and add several sentences in this section.
Recently we started doing sync-safekeepers before exiting compute_ctl,
expecting that it will make next sync faster by skipping recovery. But
recovery is still running in some cases
(https://github.com/neondatabase/neon/pull/4574#issuecomment-1629256166)
because of the lagging truncateLsn. This PR should help with updating
truncateLsn.
This addresses the issue in #4526 by adding a test that reproduces the
race condition that gave rise to the bug (or at least *a* race condition
that gave rise to the same error message), and then implementing a fix
that just prints a message to the log if a file could not been found for
uploading. Even though the underlying race condition is not fixed yet,
this will un-block the upload queue in that situation, greatly reducing
the impact of such a (rare) race.
Fixes#4526.
## Problem
Postgres submodule can be changed unintentionally, and these changes are
easy to miss during the review.
Adding a check that should prevent this from happening, the check fails
`build-neon` job with the following message:
```
Expected postgres-v14 rev to be at '1414141414141414141414141414141414141414', but it is at '1144aee1661c79eec65e784a8dad8bd450d9df79'
Expected postgres-v15 rev to be at '1515151515151515151515151515151515151515', but it is at '1984832c740a7fa0e468bb720f40c525b652835d'
Please update vendors/revisions.json if these changes are intentional.
```
This is an alternative approach to
https://github.com/neondatabase/neon/pull/4603
## Summary of changes
- Add `vendor/revisions.json` file with expected revisions
- Add built-time check (to `build-neon` job) that Postgres submodules
match revisions from `vendor/revisions.json`
- A couple of small improvements for logs from
https://github.com/neondatabase/neon/pull/4603
- Fixed GitHub autocomment for no tests was run case
---------
Co-authored-by: Joonas Koivunen <joonas@neon.tech>
The comment referenced an issue that was already closed. Remove that
reference and replace it with an explanation why we already don't print
an error.
See discussion in
https://github.com/neondatabase/neon/issues/2934#issuecomment-1626505916
For the TOCTOU fixes, the two calls after the `.exists()` both didn't
handle the situation well where the file was deleted after the initial
`.exists()`: one would assume that the path wasn't a file, giving a bad
error, the second would give an accurate error but that's not wanted
either.
We remove both racy `exists` and `is_file` checks, and instead just look
for errors about files not being found.
## Problem
If we fail to wake up the compute node, a subsequent connect attempt
will definitely fail. However, kubernetes won't fail the connection
immediately, instead it hangs until we timeout (10s).
## Summary of changes
Refactor the loop to allow fast retries of compute_wake and to skip a
connect attempt.
## Problem
Binaries created from PRs (both in docker images and for tests) have
wrong git-env versions, they point to phantom merge commits.
## Summary of changes
- Prefer GIT_VERSION env variable even if git information was accessible
- Use `${{ github.event.pull_request.head.sha || github.sha }}` instead
of `${{ github.sha }}` for `GIT_VERSION` in workflows
So the builds will still happen from this phantom commit, but we will
report the PR commit.
---------
Co-authored-by: Joonas Koivunen <joonas@neon.tech>
## Problem
part of https://github.com/neondatabase/neon/pull/4340
## Summary of changes
Remove LayerDescriptor and remove `todo!`. At the same time, this PR
adds `AsLayerDesc` trait for all persistent layers and changed
`LayerFileManager` to have a generic type. For tests, we are now using
`LayerObject`, which is a wrapper around `PersistentLayerDesc`.
---------
Signed-off-by: Alex Chi Z <chi@neon.tech>
Before this PR, during shutdown, we'd find naked logs like this one for every active page service connection:
```
2023-07-05T14:13:50.791992Z INFO shutdown request received in run_message_loop
```
This PR
1. adds a peer_addr span field to distinguish the connections in logs
2. sets the tenant_id / timeline_id fields earlier
It would be nice to have `tenant_id` and `timeline_id` directly on
the `page_service_conn_main` span (empty, initially), then set
them at the top of `process_query`.
The problem is that the debug asserts for `tenant_id` and
`timeline_id` presence in the tracing span doesn't support
detecting empty values [1].
So, I'm a bit hesitant about over-using `Span::record`.
[1] https://github.com/neondatabase/neon/issues/4676
We see the following log lines occasionally in prod:
```
kill_and_wait_impl{pid=1983042}: wait successful exit_status=signal: 9 (SIGKILL)
```
This PR makes it easier to find the tenant for the pid, by including the
tenant id as a field in the span.
It started from few config methods that have various orderings and
sometimes use references sometimes not. So I unified path manipulation
methods to always order tenant_id before timeline_id and use referenced
because we dont need owned values.
Similar changes happened to call-sites of config methods.
I'd say its a good idea to always order tenant_id before timeline_id so
it is consistent across the whole codebase.
## Problem
`docker build ... -f Dockerfile.compute-node ...` fails on ARM (I'm
checking on macOS).
## Summary of changes
- Download the arm version of cmake on arm
## Problem
#4598 compute nodes are not accessible some time after wake up due to
kubernetes DNS not being fully propagated.
## Summary of changes
Update connect retry mechanism to support handling IO errors and
sleeping for 100ms
## Checklist before requesting a review
- [x] I have performed a self-review of my code.
- [ ] If it is a core feature, I have added thorough tests.
- [ ] Do we need to implement analytics? if so did you add the relevant
metrics to the dashboard?
- [ ] If this PR requires public announcement, mark it with
/release-notes label and add several sentences in this section.
## Problem
I was reading the code of the page server today and found these minor
things that I thought could be cleaned up.
## Summary of changes
* remove a redundant indentation layer and continue in the flushing loop
* use the builtin `PartialEq` check instead of hand-rolling a `range_eq`
function
* Add a missing `>` to a prominent doc comment
General Rust Write trait semantics (as well as its async brother) is that write
definitely happens only after Write::flush(). This wasn't needed in sync where
rust write calls the syscall directly, but is required in async.
Also fix setting initial end_pos in walsender, sometimes it was from the future.
fixes https://github.com/neondatabase/neon/issues/4518
## Problem
Compute is not always able to reconnect to pages server.
First of all it caused by long time of restart of pageserver.
So number of attempts is increased from 5 (hardcoded) to 60 (GUC).
Also we do not perform flush after each command to increase performance
(it is especially critical for prefetch).
Unfortunately such pending flush makes it not possible to transparently
reconnect to restarted pageserver.
What we can do is to try to minimzie such probabilty.
Most likely broken connection will be detected in first sens command
after some idle period.
This is why max_flush_delay parameter is added which force flush to be
performed after first request after some idle period.
See #4497
## Summary of changes
Add neon.max_reconnect_attempts and neon.max_glush_delay GUCs which
contol when flush has to be done
and when it is possible to try to reconnect to page server
## Checklist before requesting a review
- [ ] I have performed a self-review of my code.
- [ ] If it is a core feature, I have added thorough tests.
- [ ] Do we need to implement analytics? if so did you add the relevant
metrics to the dashboard?
- [ ] If this PR requires public announcement, mark it with
/release-notes label and add several sentences in this section.
## Checklist before merging
- [ ] Do not forget to reformat commit message to not include the above
checklist
## Problem
- Running the command according to docker.md gives warning and error.
- Warning `permissions should be u=rw (0600) or less` is output when
executing `psql -h localhost -p 55433 -U cloud_admin`.
- `FATAL: password authentication failed for user "root”` is output in
compute logs.
## Summary of changes
- Add `$ chmod 600 ~/.pgpass` in docker.md to avoid warning.
- Add username (cloud_admin) to pg_isready command in docker-compose.yml
to avoid error.
---------
Co-authored-by: Tomoka Hayashi <tomoka.hayashi@ntt.com>
```
CREATE EXTENSION embedding;
CREATE TABLE t (val real[]);
INSERT INTO t (val) VALUES ('{0,0,0}'), ('{1,2,3}'), ('{1,1,1}'), (NULL);
CREATE INDEX ON t USING hnsw (val) WITH (maxelements = 10, dims=3, m=3);
INSERT INTO t (val) VALUES (array[1,2,4]);
SELECT * FROM t ORDER BY val <-> array[3,3,3];
val
---------
{1,2,3}
{1,2,4}
{1,1,1}
{0,0,0}
(5 rows)
```
```
CREATE EXTENSION embedding;
CREATE TABLE t (val real[]);
INSERT INTO t (val) VALUES ('{0,0,0}'), ('{1,2,3}'), ('{1,1,1}'), (NULL);
CREATE INDEX ON t USING hnsw (val) WITH (maxelements = 10, dims=3, m=3);
INSERT INTO t (val) VALUES (array[1,2,4]);
SELECT * FROM t ORDER BY val <-> array[3,3,3];
val
---------
{1,2,3}
{1,2,4}
{1,1,1}
{0,0,0}
(5 rows)
```
Does three things:
* add a `Display` impl for `LayerFileName` equal to the `short_id`
* based on that, replace the `Layer::short_id` function by a requirement
for a `Display` impl
* use that `Display` impl in the places where the `short_id` and `file_name()` functions were used instead
Fixes#4145
Looking at logs from staging and prod, I found there are a bunch of log
lines without tenant / timeline context.
Manully walk through all task_mgr::spawn lines and fix that using the
least amount of work required.
While doing it, remove some redundant `shutting down` messages.
refs https://github.com/neondatabase/neon/issues/4222
After announcing `hnsw`, there is a hypothesis that the community will
start comparing it with `pgvector` by themselves. Therefore, let's have
an actual version of `pgvector` in Neon.
Cache up to 20 connections per endpoint. Once all pooled connections
are used current implementation can open an extra connection, so the
maximum number of simultaneous connections is not enforced.
There are more things to do here, especially with background clean-up
of closed connections, and checks for transaction state. But current
implementation allows to check for smaller coonection latencies that
this cache should bring.
## Problem
HNSW index is created in memory.
Try to prevent OOM by checking of available RAM.
## Summary of changes
## Checklist before requesting a review
- [ ] I have performed a self-review of my code.
- [ ] If it is a core feature, I have added thorough tests.
- [ ] Do we need to implement analytics? if so did you add the relevant
metrics to the dashboard?
- [ ] If this PR requires public announcement, mark it with
/release-notes label and add several sentences in this section.
## Checklist before merging
- [ ] Do not forget to reformat commit message to not include the above
checklist
---------
Co-authored-by: Konstantin Knizhnik <knizhnik@neon.tech>
In case we try to connect to an outdated address that is no longer valid, the
default behavior of Kubernetes is to drop the packets, causing us to wait for
the entire timeout period. We want to fail fast in such cases.
A specific case to consider is when we have cached compute node information
with a 5-minute TTL (Time To Live), but the user has executed a `/suspend` API
call, resulting in the nonexistence of the compute node.
## Problem
While pbkdf2 is a simple algorithm, we should probably use a well tested
implementation
## Summary of changes
* Use pbkdf2 crate
* Use arrays like the hmac comment says
## Checklist before requesting a review
- [X] I have performed a self-review of my code.
- [X] If it is a core feature, I have added thorough tests.
- [ ] Do we need to implement analytics? if so did you add the relevant
metrics to the dashboard?
- [ ] If this PR requires public announcement, mark it with
/release-notes label and add several sentences in this section.
The consumption metrics synthetic size worker does logical size calculation.
Logical size calculation currently does synchronous disk IO.
This blocks the MGMT_REQUEST_RUNTIME's executor threads, starving other futures.
While there's work on the way to move the synchronous disk IO into spawn_blocking,
the quickfix here is to use the BACKGROUND_RUNTIME instead of MGMT_REQUEST_RUNTIME.
Actually it's not just a quickfix. We simply shouldn't be blocking MGMT_REQUEST_RUNTIME
executor threads on CPU or sync disk IO.
That work isn't done yet, as many of the mgmt tasks still _do_ disk IO.
But it's not as intensive as the logical size calculations that we're fixing here.
While we're at it, fix disk-usage-based eviction in a similar way.
It wasn't the culprit here, according to prod logs, but it can theoretically be
a little CPU-intensive.
More context, including graphs from Prod:
https://neondb.slack.com/archives/C03F5SM1N02/p1687541681336949
(cherry picked from commit d6e35222ea)
This commit introduces an SQL-over-HTTP endpoint in the proxy, with a JSON
response structure resembling that of the node-postgres driver. This method,
using HTTP POST, achieves smaller amortized latencies in edge setups due to
fewer round trips and an enhanced open connection reuse by the v8 engine.
This update involves several intricacies:
1. SQL injection protection: We employed the extended query protocol, modifying
the rust-postgres driver to send queries in one roundtrip using a text
protocol rather than binary, bypassing potential issues like those identified
in https://github.com/sfackler/rust-postgres/issues/1030.
2. Postgres type compatibility: As not all postgres types have binary
representations (e.g., acl's in pg_class), we adjusted rust-postgres to
respond with text protocol, simplifying serialization and fixing queries with
text-only types in response.
3. Data type conversion: Considering JSON supports fewer data types than
Postgres, we perform conversions where possible, passing all other types as
strings. Key conversions include:
- postgres int2, int4, float4, float8 -> json number (NaN and Inf remain
text)
- postgres bool, null, text -> json bool, null, string
- postgres array -> json array
- postgres json and jsonb -> json object
4. Alignment with node-postgres: To facilitate integration with js libraries,
we've matched the response structure of node-postgres, returning command tags
and column oids. Command tag capturing was added to the rust-postgres
functionality as part of this change.
## Problem
Compatibility tests don't support Postgres 15 yet, but we're still
trying to upload compatibility snapshot (which we do not collect).
Ref
https://github.com/neondatabase/neon/actions/runs/4991394158/jobs/8940369368#step:4:38129
## Summary of changes
Add `pg_version` parameter to `run-python-test-set` actions and do not
upload compatibility snapshot for Postgres 15
This reverts commit 732acc5.
Reverted PR: #3869
As noted in PR #4094, we do in fact try to insert duplicates to the
layer map, if L0->L1 compaction is interrupted. We do not have a proper
fix for that right now, and we are in a hurry to make a release to
production, so revert the changes related to this to the state that we
have in production currently. We know that we have a bug here, but
better to live with the bug that we've had in production for a long
time, than rush a fix to production without testing it in staging first.
Cc: #4094, #4088
Otherwise they get lost. Normally buffer is empty before proxy pass, but this is
not the case with pipeline mode of out npm driver; fixes connection hangup
introduced by b80fe41af3 for it.
fixes https://github.com/neondatabase/neon/issues/3822
## Describe your changes
We have previously changed the neon-proxy to use RollingUpdate. This
should be enabled in legacy proxy too in order to avoid breaking
connections for the clients and allow for example backups to run even
during deployment. (https://github.com/neondatabase/neon/pull/3683)
## Issue ticket number and link
https://github.com/neondatabase/neon/issues/3333
## Describe your changes
Rebase vendored PostgreSQL onto 14.7 and 15.2
## Issue ticket number and link
#3579
## Checklist before requesting a review
- [x] I have performed a self-review of my code.
- [x] If it is a core feature, I have added thorough tests.
- [ ] Do we need to implement analytics? if so did you add the relevant
metrics to the dashboard?
- [x] If this PR requires public announcement, mark it with
/release-notes label and add several sentences in this section.
```
The version of PostgreSQL that we use is updated to 14.7 for PostgreSQL
14 and 15.2 for PostgreSQL 15.
```
previously we applied the ratelimiting only up to receiving the headers
from s3, or somewhere near it. the commit adds an adapter which carries
the permit until the AsyncRead has been disposed.
fixes#3662.
Calculation of logical size is now async because of layer downloads, so
we shouldn't use spawn_blocking for it. Use of `spawn_blocking`
exhausted resources which are needed by `tokio::io::copy` when copying
from a stream to a file which lead to deadlock.
Fixes: #3657
these are happening in tests because of #3655 but they sure took some
time to appear.
makes the `Compaction failed, retrying in 2s: Cannot run compaction
iteration on inactive tenant` into a globally allowed error, because it
has been seen failing on different test cases.
Small changes, but hopefully this will help with the panic detected in
staging, for which we cannot get the debugging information right now
(end-of-branch before branch-point).
Before only the timelines which have passed the `gc_horizon` were
processed which failed with orphans at the tree_sort phase. Example
input in added `test_branched_empty_timeline_size` test case.
The PR changes iteration to happen through all timelines, and in
addition to that, any learned branch points will be calculated as they
would had been in the original implementation if the ancestor branch had
been over the `gc_horizon`.
This also changes how tenants where all timelines are below `gc_horizon`
are handled. Previously tenant_size 0 was returned, but now they will
have approximately `initdb_lsn` worth of tenant_size.
The PR also adds several new tenant size tests that describe various corner
cases of branching structure and `gc_horizon` setting.
They are currently disabled to not consume time during CI.
Co-authored-by: Joonas Koivunen <joonas@neon.tech>
Co-authored-by: Anastasia Lubennikova <anastasia@neon.tech>
Previously, we were trying to re-assign owned objects of the already
deleted role. This were causing a crash loop in the case when compute
was restarted with a spec that includes delta operation for role
deletion. To avoid such cases, check that role is still present before
calling `reassign_owned_objects`.
Resolvesneondatabase/cloud#3553
This reverts commit 826e89b9ce.
The problem with that commit was that it deletes the TempDir while
there are still EphemeralFile instances open.
At first I thought this could be fixed by simply adding
Handle::current().block_on(task_mgr::shutdown(None, Some(tenant_id), None))
to TenantHarness::drop, but it turned out to be insufficient.
So, reverting the commit until we find a proper solution.
refs https://github.com/neondatabase/neon/issues/3385
Refactors Compute::prepare_and_run. It's split into subroutines
differently, to make it easier to attach tracing spans to the
different stages. The high-level logic for waiting for Postgres to
exit is moved to the caller.
Replace 'env_logger' with 'tracing', and add `#instrument` directives
to different stages fo the startup process. This is a fairly
mechanical change, except for the changes in 'spec.rs'. 'spec.rs'
contained some complicated formatting, where parts of log messages
were printed directly to stdout with `print`s. That was a bit messed
up because the log normally goes to stderr, but those lines were
printed to stdout. In our docker images, stderr and stdout both go to
the same place so you wouldn't notice, but I don't think it was
intentional.
This changes the log format to the default
'tracing_subscriber::format' format. It's different from the Postgres
log format, however, and because both compute_tools and Postgres print
to the same log, it's now a mix of two different formats. I'm not
sure how the Grafana log parsing pipeline can handle that. If it's a
problem, we can build custom formatter to change the compute_tools log
format to be the same as Postgres's, like it was before this commit,
or we can change the Postgres log format to match tracing_formatter's,
or we can start printing compute_tool's log output to a different
destination than Postgres
IMDSv2 has limits, and if we query it on every s3 interaction we are
going to go over those limits. Changes the s3_bucket client
configuration to use:
- ChainCredentialsProvider to handle env variables or imds usage
- LazyCachingCredentialsProvider to actually cache any credentials
Related: https://github.com/awslabs/aws-sdk-rust/issues/629
Possibly related: https://github.com/neondatabase/neon/issues/3118
plv8 can only be built with a fairly new gold linker version. We used to install
it via binutils packages from testing, but it also updates libc and that causes
troubles in the resulting image as different extensions were built against
different libc versions. We could either use libc from debian-testing everywhere
or restrain from using testing packages and install necessary programs manually.
This patch uses the latter approach: gold for plv8 and cmake for h3 are
installed manually.
In a passing declare h3_postgis as a safe extension (previous omission).
`GRANT CREATE ON SCHEMA public` fails if there is no schema `public`.
Disable it in release for now and make a better fix later (it is
needed for v15 support).
* Check for entire range during sasl validation (#2281)
* Gen2 GH runner (#2128)
* Re-add rustup override
* Try s3 bucket
* Set git version
* Use v4 cache key to prevent problems
* Switch to v5 for key
* Add second rustup fix
* Rebase
* Add kaniko steps
* Fix typo and set compress level
* Disable global run default
* Specify shell for step
* Change approach with kaniko
* Try less verbose shell spec
* Add submodule pull
* Add promote step
* Adjust dependency chain
* Try default swap again
* Use env
* Don't override aws key
* Make kaniko build conditional
* Specify runs on
* Try without dependency link
* Try soft fail
* Use image with git
* Try passing to next step
* Fix duplicate
* Try other approach
* Try other approach
* Fix typo
* Try other syntax
* Set env
* Adjust setup
* Try step 1
* Add link
* Try global env
* Fix mistake
* Debug
* Try other syntax
* Try other approach
* Change order
* Move output one step down
* Put output up one level
* Try other syntax
* Skip build
* Try output
* Re-enable build
* Try other syntax
* Skip middle step
* Update check
* Try first step of dockerhub push
* Update needs dependency
* Try explicit dir
* Add missing package
* Try other approach
* Try other approach
* Specify region
* Use with
* Try other approach
* Add debug
* Try other approach
* Set region
* Follow AWS example
* Try github approach
* Skip Qemu
* Try stdin
* Missing steps
* Add missing close
* Add echo debug
* Try v2 endpoint
* Use v1 endpoint
* Try without quotes
* Revert
* Try crane
* Add debug
* Split steps
* Fix duplicate
* Add shell step
* Conform to options
* Add verbose flag
* Try single step
* Try workaround
* First request fails hunch
* Try bullseye image
* Try other approach
* Adjust verbose level
* Try previous step
* Add more debug
* Remove debug step
* Remove rogue indent
* Try with larger image
* Add build tag step
* Update workflow for testing
* Add tag step for test
* Remove unused
* Update dependency chain
* Add ownership fix
* Use matrix for promote
* Force update
* Force build
* Remove unused
* Add new image
* Add missing argument
* Update dockerfile copy
* Update Dockerfile
* Update clone
* Update dockerfile
* Go to correct folder
* Use correct format
* Update dockerfile
* Remove cd
* Debug find where we are
* Add debug on first step
* Changedir to postgres
* Set workdir
* Use v1 approach
* Use other dependency
* Try other approach
* Try other approach
* Update dockerfile
* Update approach
* Update dockerfile
* Update approach
* Update dockerfile
* Update dockerfile
* Add workspace hack
* Update Dockerfile
* Update Dockerfile
* Update Dockerfile
* Change last step
* Cleanup pull in prep for review
* Force build images
* Add condition for latest tagging
* Use pinned version
* Try without name value
* Remove more names
* Shorten names
* Add kaniko comments
* Pin kaniko
* Pin crane and ecr helper
* Up one level
* Switch to pinned tag for rust image
* Force update for test
Co-authored-by: Rory de Zoete <rdezoete@RorysMacStudio.fritz.box>
Co-authored-by: Rory de Zoete <rdezoete@b04468bf-cdf4-41eb-9c94-aff4ca55e4bf.fritz.box>
Co-authored-by: Rory de Zoete <rdezoete@Rorys-Mac-Studio.fritz.box>
Co-authored-by: Rory de Zoete <rdezoete@4795e9ee-4f32-401f-85f3-f316263b62b8.fritz.box>
Co-authored-by: Rory de Zoete <rdezoete@2f8bc4e5-4ec2-4ea2-adb1-65d863c4a558.fritz.box>
Co-authored-by: Rory de Zoete <rdezoete@27565b2b-72d5-4742-9898-a26c9033e6f9.fritz.box>
Co-authored-by: Rory de Zoete <rdezoete@ecc96c26-c6c4-4664-be6e-34f7c3f89a3c.fritz.box>
Co-authored-by: Rory de Zoete <rdezoete@7caff3a5-bf03-4202-bd0e-f1a93c86bdae.fritz.box>
* Add missing step output, revert one deploy step (#2285)
* Add missing step output, revert one deploy step
* Conform to syntax
* Update approach
* Add missing value
* Add missing needs
Co-authored-by: Rory de Zoete <rdezoete@RorysMacStudio.fritz.box>
* Error for fatal not git repo (#2286)
Co-authored-by: Rory de Zoete <rdezoete@RorysMacStudio.fritz.box>
* Use main, not branch for ref check (#2288)
* Use main, not branch for ref check
* Add more debug
* Count main, not head
* Try new approach
* Conform to syntax
* Update approach
* Get full history
* Skip checkout
* Cleanup debug
* Remove more debug
Co-authored-by: Rory de Zoete <rdezoete@RorysMacStudio.fritz.box>
* Fix docker zombie process issue (#2289)
* Fix docker zombie process issue
* Init everywhere
Co-authored-by: Rory de Zoete <rdezoete@RorysMacStudio.fritz.box>
* Fix 1.63 clippy lints (#2282)
* split out timeline metrics, track layer map loading and size calculation
* reset rust cache for clippy run to avoid an ICE
additionally remove trailing whitespaces
* Rename pg_control_ffi.h to bindgen_deps.h, for clarity.
The pg_control_ffi.h name implies that it only includes stuff related to
pg_control.h. That's mostly true currently, but really the point of the
file is to include everything that we need to generate Rust definitions
from.
* Make local mypy behave like CI mypy (#2291)
* Fix flaky pageserver restarts in tests (#2261)
* Remove extra type aliases (#2280)
* Update cachepot endpoint (#2290)
* Update cachepot endpoint
* Update dockerfile & remove env
* Update image building process
* Cannot use metadata endpoint for this
* Update workflow
* Conform to kaniko syntax
* Update syntax
* Update approach
* Update dockerfiles
* Force update
* Update dockerfiles
* Update dockerfile
* Cleanup dockerfiles
* Update s3 test location
* Revert s3 experiment
* Add more debug
* Specify aws region
* Remove debug, add prefix
* Remove one more debug
Co-authored-by: Rory de Zoete <rdezoete@RorysMacStudio.fritz.box>
* workflows/benchmarking: increase timeout (#2294)
* Rework `init` in pageserver CLI (#2272)
* Do not create initial tenant and timeline (adjust Python tests for that)
* Rework config handling during init, add --update-config to manage local config updates
* Fix: Always build images (#2296)
* Always build images
* Remove unused
Co-authored-by: Rory de Zoete <rdezoete@RorysMacStudio.fritz.box>
* Move auto-generated 'bindings' to a separate inner module.
Re-export only things that are used by other modules.
In the future, I'm imagining that we run bindgen twice, for Postgres
v14 and v15. The two sets of bindings would go into separate
'bindings_v14' and 'bindings_v15' modules.
Rearrange postgres_ffi modules.
Move function, to avoid Postgres version dependency in timelines.rs
Move function to generate a logical-message WAL record to postgres_ffi.
* fix cargo test
* Fix walreceiver and safekeeper bugs (#2295)
- There was an issue with zero commit_lsn `reason: LaggingWal { current_commit_lsn: 0/0, new_commit_lsn: 1/6FD90D38, threshold: 10485760 } }`. The problem was in `send_wal.rs`, where we initialized `end_pos = Lsn(0)` and in some cases sent it to the pageserver.
- IDENTIFY_SYSTEM previously returned `flush_lsn` as a physical end of WAL. Now it returns `flush_lsn` (as it was) to walproposer and `commit_lsn` to everyone else including pageserver.
- There was an issue with backoff where connection was cancelled right after initialization: `connected!` -> `safekeeper_handle_db: Connection cancelled` -> `Backoff: waiting 3 seconds`. The problem was in sleeping before establishing the connection. This is fixed by reworking retry logic.
- There was an issue with getting `NoKeepAlives` reason in a loop. The issue is probably the same as the previous.
- There was an issue with filtering safekeepers based on retry attempts, which could filter some safekeepers indefinetely. This is fixed by using retry cooldown duration instead of retry attempts.
- Some `send_wal.rs` connections failed with errors without context. This is fixed by adding a timeline to safekeepers errors.
New retry logic works like this:
- Every candidate has a `next_retry_at` timestamp and is not considered for connection until that moment
- When walreceiver connection is closed, we update `next_retry_at` using exponential backoff, increasing the cooldown on every disconnect.
- When `last_record_lsn` was advanced using the WAL from the safekeeper, we reset the retry cooldown and exponential backoff, allowing walreceiver to reconnect to the same safekeeper instantly.
* on safekeeper registration pass availability zone param (#2292)
Co-authored-by: Kirill Bulatov <kirill@neon.tech>
Co-authored-by: Rory de Zoete <33318916+zoete@users.noreply.github.com>
Co-authored-by: Rory de Zoete <rdezoete@RorysMacStudio.fritz.box>
Co-authored-by: Rory de Zoete <rdezoete@b04468bf-cdf4-41eb-9c94-aff4ca55e4bf.fritz.box>
Co-authored-by: Rory de Zoete <rdezoete@Rorys-Mac-Studio.fritz.box>
Co-authored-by: Rory de Zoete <rdezoete@4795e9ee-4f32-401f-85f3-f316263b62b8.fritz.box>
Co-authored-by: Rory de Zoete <rdezoete@2f8bc4e5-4ec2-4ea2-adb1-65d863c4a558.fritz.box>
Co-authored-by: Rory de Zoete <rdezoete@27565b2b-72d5-4742-9898-a26c9033e6f9.fritz.box>
Co-authored-by: Rory de Zoete <rdezoete@ecc96c26-c6c4-4664-be6e-34f7c3f89a3c.fritz.box>
Co-authored-by: Rory de Zoete <rdezoete@7caff3a5-bf03-4202-bd0e-f1a93c86bdae.fritz.box>
Co-authored-by: Dmitry Rodionov <dmitry@neon.tech>
Co-authored-by: Heikki Linnakangas <heikki@neon.tech>
Co-authored-by: bojanserafimov <bojan.serafimov7@gmail.com>
Co-authored-by: Alexander Bayandin <alexander@neon.tech>
Co-authored-by: Anastasia Lubennikova <anastasia@neon.tech>
Co-authored-by: Anton Galitsyn <agalitsyn@users.noreply.github.com>
* github/workflows: Fix git dubious ownership (#2223)
* Move relation size cache from WalIngest to DatadirTimeline (#2094)
* Move relation sie cache to layered timeline
* Fix obtaining current LSN for relation size cache
* Resolve merge conflicts
* Resolve merge conflicts
* Reestore 'lsn' field in DatadirModification
* adjust DatadirModification lsn in ingest_record
* Fix formatting
* Pass lsn to get_relsize
* Fix merge conflict
* Update pageserver/src/pgdatadir_mapping.rs
Co-authored-by: Heikki Linnakangas <heikki@zenith.tech>
* Update pageserver/src/pgdatadir_mapping.rs
Co-authored-by: Heikki Linnakangas <heikki@zenith.tech>
Co-authored-by: Heikki Linnakangas <heikki@zenith.tech>
* refactor: replace lazy-static with once-cell (#2195)
- Replacing all the occurrences of lazy-static with `once-cell::sync::Lazy`
- fixes#1147
Signed-off-by: Ankur Srivastava <best.ankur@gmail.com>
* Add more buckets to pageserver latency metrics (#2225)
* ignore record property warning to fix benchmarks
* increase statement timeout
* use event so it fires only if workload thread successfully finished
* remove debug log
* increase timeout to pass test with real s3
* avoid duplicate parameter, increase timeout
* Major migration script (#2073)
This script can be used to migrate a tenant across breaking storage versions, or (in the future) upgrading postgres versions. See the comment at the top for an overview.
Co-authored-by: Anastasia Lubennikova <anastasia@neon.tech>
* Fix etcd typos
* Fix links to safekeeper protocol docs. (#2188)
safekeeper/README_PROTO.md was moved to docs/safekeeper-protocol.md in
commit 0b14fdb078, as part of reorganizing the docs into 'mdbook' format.
Fixes issue #1475. Thanks to @banks for spotting the outdated references.
In addition to fixing the above issue, this patch also fixes other broken links as a result of 0b14fdb078. See https://github.com/neondatabase/neon/pull/2188#pullrequestreview-1055918480.
Co-authored-by: Heikki Linnakangas <heikki@neon.tech>
Co-authored-by: Thang Pham <thang@neon.tech>
* Update CONTRIBUTING.md
* Update CONTRIBUTING.md
* support node id and remote storage params in docker_entrypoint.sh
* Safe truncate (#2218)
* Move relation sie cache to layered timeline
* Fix obtaining current LSN for relation size cache
* Resolve merge conflicts
* Resolve merge conflicts
* Reestore 'lsn' field in DatadirModification
* adjust DatadirModification lsn in ingest_record
* Fix formatting
* Pass lsn to get_relsize
* Fix merge conflict
* Update pageserver/src/pgdatadir_mapping.rs
Co-authored-by: Heikki Linnakangas <heikki@zenith.tech>
* Update pageserver/src/pgdatadir_mapping.rs
Co-authored-by: Heikki Linnakangas <heikki@zenith.tech>
* Check if relation exists before trying to truncat it
refer #1932
* Add test reporducing FSM truncate problem
Co-authored-by: Heikki Linnakangas <heikki@zenith.tech>
* Fix exponential backoff values
* Update back `vendor/postgres` back; it was changed accidentally. (#2251)
Commit 4227cfc96e accidentally reverted vendor/postgres to an older
version. Update it back.
* Add pageserver checkpoint_timeout option.
To flush inmemory layer eventually when no new data arrives, which helps
safekeepers to suspend activity (stop pushing to the broker). Default 10m should
be ok.
* Share exponential backoff code and fix logic for delete task failure (#2252)
* Fix bug when import large (>1GB) relations (#2172)
Resolves#2097
- use timeline modification's `lsn` and timeline's `last_record_lsn` to determine the corresponding LSN to query data in `DatadirModification::get`
- update `test_import_from_pageserver`. Split the test into 2 variants: `small` and `multisegment`.
+ `small` is the old test
+ `multisegment` is to simulate #2097 by using a larger number of inserted rows to create multiple segment files of a relation. `multisegment` is configured to only run with a `release` build
* Fix timeline physical size flaky tests (#2244)
Resolves#2212.
- use `wait_for_last_flush_lsn` in `test_timeline_physical_size_*` tests
## Context
Need to wait for the pageserver to catch up with the compute's last flush LSN because during the timeline physical size API call, it's possible that there are running `LayerFlushThread` threads. These threads flush new layers into disk and hence update the physical size. This results in a mismatch between the physical size reported by the API and the actual physical size on disk.
### Note
The `LayerFlushThread` threads are processed **concurrently**, so it's possible that the above error still persists even with this patch. However, making the tests wait to finish processing all the WALs (not flushing) before calculating the physical size should help reduce the "flakiness" significantly
* postgres_ffi/waldecoder: validate more header fields
* postgres_ffi/waldecoder: remove unused startlsn
* postgres_ffi/waldecoder: introduce explicit `enum State`
Previously it was emulated with a combination of nullable fields.
This change should make the logic more readable.
* disable `test_import_from_pageserver_multisegment` (#2258)
This test failed consistently on `main` now. It's better to temporarily disable it to avoid blocking others' PRs while investigating the root cause for the test failure.
See: #2255, #2256
* get_binaries uses DOCKER_TAG taken from docker image build step (#2260)
* [proxy] Rework wire format of the password hack and some errors (#2236)
The new format has a few benefits: it's shorter, simpler and
human-readable as well. We don't use base64 anymore, since
url encoding got us covered.
We also show a better error in case we couldn't parse the
payload; the users should know it's all about passing the
correct project name.
* test_runner/pg_clients: collect docker logs (#2259)
* get_binaries script fix (#2263)
* get_binaries uses DOCKER_TAG taken from docker image build step
* remove docker tag discovery at all and fix get_binaries for version variable
* Better storage sync logs (#2268)
* Find end of WAL on safekeepers using WalStreamDecoder.
We could make it inside wal_storage.rs, but taking into account that
- wal_storage.rs reading is async
- we don't need s3 here
- error handling is different; error during decoding is normal
I decided to put it separately.
Test
cargo test test_find_end_of_wal_last_crossing_segment
prepared earlier by @yeputons passes now.
Fixes https://github.com/neondatabase/neon/issues/544https://github.com/neondatabase/cloud/issues/2004
Supersedes https://github.com/neondatabase/neon/pull/2066
* Improve walreceiver logic (#2253)
This patch makes walreceiver logic more complicated, but it should work better in most cases. Added `test_wal_lagging` to test scenarios where alive safekeepers can lag behind other alive safekeepers.
- There was a bug which looks like `etcd_info.timeline.commit_lsn > Some(self.local_timeline.get_last_record_lsn())` filtered all safekeepers in some strange cases. I removed this filter, it should probably help with #2237
- Now walreceiver_connection reports status, including commit_lsn. This allows keeping safekeeper connection even when etcd is down.
- Safekeeper connection now fails if pageserver doesn't receive safekeeper messages for some time. Usually safekeeper sends messages at least once per second.
- `LaggingWal` check now uses `commit_lsn` directly from safekeeper. This fixes the issue with often reconnects, when compute generates WAL really fast.
- `NoWalTimeout` is rewritten to trigger only when we know about the new WAL and the connected safekeeper doesn't stream any WAL. This allows setting a small `lagging_wal_timeout` because it will trigger only when we observe that the connected safekeeper has stuck.
* increase timeout in wait_for_upload to avoid spurious failures when testing with real s3
* Bump vendor/postgres to include XLP_FIRST_IS_CONTRECORD fix. (#2274)
* Set up a workflow to run pgbench against captest (#2077)
Signed-off-by: Ankur Srivastava <best.ankur@gmail.com>
Co-authored-by: Alexander Bayandin <alexander@neon.tech>
Co-authored-by: Konstantin Knizhnik <knizhnik@garret.ru>
Co-authored-by: Heikki Linnakangas <heikki@zenith.tech>
Co-authored-by: Ankur Srivastava <ansrivas@users.noreply.github.com>
Co-authored-by: bojanserafimov <bojan.serafimov7@gmail.com>
Co-authored-by: Dmitry Rodionov <dmitry@neon.tech>
Co-authored-by: Anastasia Lubennikova <anastasia@neon.tech>
Co-authored-by: Kirill Bulatov <kirill@neon.tech>
Co-authored-by: Heikki Linnakangas <heikki@neon.tech>
Co-authored-by: Thang Pham <thang@neon.tech>
Co-authored-by: Stas Kelvich <stas.kelvich@gmail.com>
Co-authored-by: Arseny Sher <sher-ars@yandex.ru>
Co-authored-by: Egor Suvorov <egor@neon.tech>
Co-authored-by: Andrey Taranik <andrey@cicd.team>
Co-authored-by: Dmitry Ivanov <ivadmi5@gmail.com>
[HOTFIX] Release deploy fix
This PR uses this branch neondatabase/postgres#171 and several required commits from the main to use only locally built compute-tools. This should allow us to rollout safekeepers sync issue fix on prod
gh workflow --repo neondatabase/aws run deploy-dev.yml --ref main -f branch=main -f dockerTag=${{needs.tag.outputs.build-tag}}
gh workflow --repo neondatabase/aws run deploy-dev.yml --ref main -f branch=main -f dockerTag=${{needs.tag.outputs.build-tag}} -f deployPreprodRegion=false
# TODO: move deployPreprodRegion to release (`"$GITHUB_REF_NAME" == "release"` block), once Staging support different compute tag prefixes for different regions
gh workflow --repo neondatabase/aws run deploy-dev.yml --ref main -f branch=main -f dockerTag=${{needs.tag.outputs.build-tag}} -f deployPreprodRegion=true
elif [[ "$GITHUB_REF_NAME" == "release" ]]; then
gh workflow --repo neondatabase/aws run deploy-prod.yml --ref main -f branch=main -f dockerTag=${{needs.tag.outputs.build-tag}} -f disclamerAcknowledged=true
else
@@ -1033,20 +1109,35 @@ jobs:
# Retry script for 5XX server errors: https://github.com/actions/github-script#retries
@@ -27,3 +27,28 @@ your patch's fault. Help to fix the root cause if something else has
broken the CI, before pushing.
*Happy Hacking!*
# How to run a CI pipeline on Pull Requests from external contributors
_An instruction for maintainers_
## TL;DR:
- Review the PR
- If and only if it looks **safe** (i.e. it doesn't contain any malicious code which could expose secrets or harm the CI), then:
- Press the "Approve and run" button in GitHub UI
- Add the `approved-for-ci-run` label to the PR
Repeat all steps after any change to the PR.
- When the changes are ready to get merged — merge the original PR (not the internal one)
## Longer version:
GitHub Actions triggered by the `pull_request` event don't share repository secrets with the forks (for security reasons).
So, passing the CI pipeline on Pull Requests from external contributors is impossible.
We're using the following approach to make it work:
- After the review, assign the `approved-for-ci-run` label to the PR if changes look safe
- A GitHub Action will create an internal branch and a new PR with the same changes (for example, for a PR `#1234`, it'll be a branch `ci-run/pr-1234`)
- Because the PR is created from the internal branch, it is able to access repository secrets (that's why it's crucial to make sure that the PR doesn't contain any malicious code that could expose our secrets or intentionally harm the CI)
- The label gets removed automatically, so to run CI again with new changes, the label should be added again (after the review)
For details see [`approved-for-ci-run.yml`](.github/workflows/approved-for-ci-run.yml)
Building Neon requires 3.15+ version of `protoc` (protobuf-compiler). If your distribution provides an older version, you can install a newer version from [here](https://github.com/protocolbuffers/protobuf/releases).
### How to add new extension to the Extension Storage?
Simply upload build artifacts to the S3 bucket.
Implement a CI step for that. Splitting it from compute-node-image build.
### How do we deal with extension versions and updates?
Currently, we rebuild extensions on every compute-node-image build and store them in the <build-version> prefix.
This is needed to ensure that `/share` and `/lib` files are in sync.
For extension updates, we rely on the PostgreSQL extension versioning mechanism (sql update scripts) and extension authors to not break backwards compatibility within one major version of PostgreSQL.
### Alternatives
For extensions written on trusted languages we can also adopt
`dbdev` PostgreSQL Package Manager based on `pg_tle` by Supabase.
This will increase the amount supported extensions and decrease the amount of work required to support them.
(This supersedes the previous proposal that looked too complicated and desynchronization-prone)
We've accumulated a bunch of problems with our approach to role and database management, namely:
1. we don't allow role and database creation from Postgres, and users are complaining about that
2. fine-grained role management is not possible both from Postgres and console
Right now, we do store users and databases both in console and Postgres, and there are two main reasons for
that:
* we want to be able to authenticate users in proxy against the console without Postgres' involvement. Otherwise,
malicious brute force attempts will wake up Postgres (expensive) and may exhaust the Postgres connections limit (deny of service).
* it is handy when we can render console UI without waking up compute (e.g., show database list)
This RFC doesn't talk about giving root access to the database, which is blocked by a secure runtime setup.
## Overview
* Add Postgres extension that sends an HTTP request each time transaction that modifies users/databases is about to commit.
* Add user management API to internal console API. Also, the console should put a JWT token into the compute so that it can access management API.
## Postgres behavior
The default user role (@username) should have `CREATE ROLE`, `CREATE DB`, and `BYPASSRLS` privileges. We expose the Postgres port
to the open internet, so we need to check password strength. Now console generates strong passwords, so there is no risk of having dumb passwords. With user-provided passwords, such risks exist.
Since we store passwords in the console we should also send unencrypted password when role is created/changed. Hence communication with the console must be encrypted. Postgres also supports creating roles using hashes, in that case, we will not be able to get a raw password. So I can see the following options here:
* roles created via SQL will *not* have raw passwords in the console
* roles created via SQL will have raw passwords in the console, except ones that were created using hashes
I'm leaning towards the second option here as it is a bit more consistent one -- if raw password storage is enabled then we store passwords in all cases where we can store them.
To send data about roles and databases from Postgres to the console we can create the following Postgres extension:
* Intercept role/database changes in `ProcessUtility_hook`. Here we have access to the query statement with the raw password. The hook handler itself should not dial the console immediately and rather stash info in some hashmap for later use.
* When the transaction is about to commit we execute collected role modifications (all as one -- console should either accept all or reject all, and hence API shouldn't be REST-like). If the console request fails we can roll back the transaction. This way if the transaction is committed we know for sure that console has this information. We can use `XACT_EVENT_PRE_COMMIT` and `XACT_EVENT_PARALLEL_PRE_COMMIT` for that.
* Extension should be mindful of the fact that it is possible to create and delete roles within the transaction.
* We also need to track who is database owner, some coding around may be needed to get the current user when the database is created.
## Console user management API
The current public API has REST API for role management. We need to have some analog for the internal API (called mgmt API in the console code). But unlike public API here we want to have an atomic way to create several roles/databases (in cases when several roles were created in the same transaction). So something like that may work:
Makes sense not to error out on duplicated create/delete operations (see failure modes)
## Managing users from the console
Now console puts a spec file with the list of databases/roles and delta operations in all the compute pods. `compute_ctl` then picks up that file and stubbornly executes deltas and checks data in the spec file is the same as in the Postgres. This way if the user creates a role in the UI we restart compute with a new spec file and during the start databases/roles are created. So if Postgres send an HTTP call each time role is created we need to break recursion in that case. We can do that based on application_name or some GUC or user (local == no HTTP hook).
Generally, we have several options when we are creating users via console:
1. restart compute with a new spec file, execute local SQL command; cut recursion in the extension
2. "push" spec files into running compute, execute local SQL command; cut recursion in the extension
3. "push" spec files into running compute, execute local SQL command; let extension create those roles in the console
4. avoid managing roles via spec files, send SQL commands to compute; let extension create those roles in the console
The last option is the most straightforward one, but with the raw password storage opt-out, we will not have the password to establish an SQL connection. Also, we need a spec for provisioning purposes and to address potential desync (but that is quite unlikely). So I think the easiest approach would be:
1. keep role management like it is now and cut the recursion in the extension when SQL is executed by compute_ctl
2. add "push" endpoint to the compute_ctl to avoid compute restart during the `apply_config` operation -- that can be done as a follow up to avoid increasing scope too much
## Failure modes
* during role creation via SQL role was created in the console but the connection was dropped before Postgres got acknowledgment or some error happened after acknowledgment (out of disk space, deadlock, etc):
in that case, Postgres won't have a role that exists in the console. Compute restart will heal it (due to the spec file). Also if the console allows repeated creation/deletion user can repeat the transaction.
# Scalability
On my laptop, I can create 4200 roles per second. That corresponds to 363 million roles per day. Since each role creation ends up in the console database we can add some limit to the number of roles (could be reasonably big to not run into it often -- like 1k or 10k).
This RFC has broad similarities to the proposal to implement a MVCC scheme in
S3 object names, but this RFC avoids a general purpose transaction scheme in
favour of more specialized "generations" that work like a transaction ID that
always has the same lifetime as a pageserver process or tenant attachment, whichever
is shorter.
## Requirements
- Accommodate storage backends with no atomic or fencing capability (i.e. work within
S3's limitation that there are no atomics and clients can't be fenced)
- Don't depend on any STONITH or node fencing in the compute layer (i.e. we will not
assume that we can reliably kill and EC2 instance and have it die)
- Scoped per-tenant, not per-pageserver; for _seamless tenant migration_, we need
per-tenant granularity, and for _failover_, we likely want to spread the workload
of the failed pageserver instance to a number of peers, rather than monolithically
moving the entire workload to another machine.
We do not rule out the latter case, but should not constrain ourselves to it.
## Design Tenets
These are not requirements, but are ideas that guide the following design:
- Avoid implementing another consensus system: we already have a strongly consistent
database in the control plane that can do atomic operations where needed, and we also
have a Paxos implementation in the safekeeper.
- Avoiding locking in to specific models of how failover will work (e.g. do not assume that
all the tenants on a pageserver will fail over as a unit).
- Be strictly correct when it comes to data integrity. Occasional failures of availability
are tolerable, occasional data loss is not.
## Non Goals
The changes in this RFC intentionally isolate the design decision of how to define
logical generations numbers and object storage format in a way that is somewhat flexible with
respect to how actual orchestration of failover works.
This RFC intentionally does not cover:
- Failure detection
- Orchestration of failover
- Standby modes to keep data ready for fast migration
- Intentional multi-writer operation on tenants (multi-writer scenarios are assumed to be transient split-brain situations).
- Sharding.
The interaction between this RFC and those features is discussed in [Appendix B](#appendix-b-interoperability-with-other-features)
## Impacted Components
pageserver, control plane, safekeeper (optional)
## Implementation Part 1: Correctness
### Summary
- A per-tenant **generation number** is introduced to uniquely identifying tenant attachments to pageserver processes.
- This generation number increments each time the control plane modifies a tenant (`Project`)'s assigned pageserver, or when the assigned pageserver restarts.
- the control plane is the authority for generation numbers: only it may
increment a generation number.
- **Object keys are suffixed** with the generation number
- **Safety for multiply-attached tenants** is provided by the
generation number in the object key: the competing pageservers will not
try to write to the same keys.
- **Safety in split brain for multiple nodes running with
the same node ID** is provided by the pageserver calling out to the control plane
on startup, to re-attach and thereby increment the generations of any attached tenants
- **Safety for deletions** is achieved by deferring the DELETE from S3 to a point in time where the deleting node has validated with control plane that no attachment with a higher generation has a reference to the to-be-DELETEd key.
- **The control plane is used to issue generation numbers** to avoid the need for
a built-in consensus system in the pageserver, although this could in principle
be changed without changing the storage format.
### Generation numbers
A generation number is associated with each tenant in the control plane,
and each time the attachment status of the tenant changes, this is incremented.
Changes in attachment status include:
- Attaching the tenant to a different pageserver
- A pageserver restarting, and "re-attaching" its tenants on startup
These increments of attachment generation provide invariants we need to avoid
split-brain issues in storage:
- If two pageservers have the same tenant attached, the attachments are guaranteed to have different generation numbers, because the generation would increment
while attaching the second one.
- If there are multiple pageservers running with the same node ID, all the attachments on all pageservers are guaranteed to have different generation numbers, because the generation would increment
when the second node started and re-attached its tenants.
As long as the infrastructure does not transparently replace an underlying
physical machine, we are totally safe. See the later [unsafe case](#unsafe-case-on-badly-behaved-infrastructure) section for details.
### Object Key Changes
#### Generation suffix
All object keys (layer objects and index objects) will contain the attachment
generation as a [suffix](#why-a-generation-suffix-rather-than-prefix).
This suffix is the primary mechanism for protecting against split-brain situations, and
enabling safe multi-attachment of tenants:
- Two pageservers running with the same node ID (e.g. after a failure, where there is
some rogue pageserver still running) will not try to write to the same objects, because at startup they will have re-attached tenants and thereby incremented
generation numbers.
- Multiple attachments (to different pageservers) of the same tenant will not try to write to the same objects, as each attachment would have a distinct generation.
The generation is appended in hex format (8 byte string representing
u32), to all our existing key names. A u32's range limit would permit
27 restarts _per second_ over a 5 year system lifetime: orders of magnitude more than
is realistic.
The exact meaning of the generation suffix can evolve over time if necessary, for
example if we chose to implement a failover mechanism internally to the pageservers
rather than going via the control plane. The storage format just sees it as a number,
with the only semantic property being that the highest numbered index is the latest.
#### Index changes
Since object keys now include a generation suffix, the index of these keys must also be updated. IndexPart currently stores keys and LSNs sufficient to reconstruct key names: this would be extended to store the generation as well.
This will increase the size of the file, but only modestly: layers are already encoded as
their string-ized form, so the overhead is about 10 bytes per layer. This will be less if/when
the index storage format is migrated to a binary format from JSON.
#### Visibility
_This section doesn't describe code changes, but extends on the consequences of the
object key changes given above_
##### Visibility of objects to pageservers
Pageservers can of course list objects in S3 at any time, but in practice their
visible set is based on the contents of their LayerMap, which is initialized
from the `index_part.json.???` that they load.
Starting with the `index_part` from the most recent previous generation
(see [loading index_part](#finding-the-remote-indices-for-timelines)), a pageserver
initially has visibility of all the objects that were referenced in the loaded index.
These objects are guaranteed to remain visible until the current generation is
superseded, via pageservers in older generations avoiding deletions (see [deletion](#deletion)).
The "most recent previous generation" is _not_ necessarily the most recent
in terms of walltime, it is the one that is readable at the time a new generation
starts. Consider the following sequence of a tenant being re-attached to different
pageserver nodes:
- Create + attach on PS1 in generation 1
- PS1 Do some work, write out index_part.json-0001
- Attach to PS2 in generation 2
- Read index_part.json-0001
- PS2 starts doing some work...
- Attach to PS3 in generation 3
- Read index_part.json-0001
- **...PS2 finishes its work: now it writes index_part.json-0002**
- PS3 writes out index_part.json-0003
In the above sequence, the ancestry of indices is:
```
0001 -> 0002
|
-> 0003
```
This is not an issue for safety: if the 0002 references some object that is
not in 0001, then 0003 simply does not see it, and will re-do whatever
work was required (e.g. ingesting WAL or doing compaction). Objects referenced
by only the 0002 index will never be read by future attachment generations, and
will eventually be cleaned up by a scrub (see [scrubbing](#cleaning-up-orphan-objects-scrubbing)).
##### Visibility of LSNs to clients
Because index_part.json is now written with a generation suffix, which data
is visible depends on which generation the reader is operating in:
- If one was passively reading from S3 from outside of a pageserver, the
visibility of data would depend on which index_part.json-<generation> file
one had chosen to read from.
- If two pageservers have the same tenant attached, they may have different
data visible as they're independently replaying the WAL, and maintaining
independent LayerMaps that are written to independent index_part.json files.
Data does not have to be remotely committed to be visible.
- For a pageserver writing with a stale generation, historic LSNs
remain readable until another pageserver (with a higher generation suffix)
decides to execute GC deletions. At this point, we may think of the stale
attachment's generation as having logically ended: during its existence
the generation had a consistent view of the world.
- For a newly attached pageserver, its highest visible LSN may appears to
go backwards with respect to an earlier attachment, if that earlier
attachment had not uploaded all data to S3 before the new attachment.
### Deletion
#### Generation number validation
While writes are de-conflicted by writers always using their own generation number in the key,
deletions are slightly more challenging: if a pageserver A is isolated, and the true active node is
pageserver B, then it is dangerous for A to do any object deletions, even of objects that it wrote
itself, because pageserver's B metadata might reference those objects.
We solve this by inserting a "generation validation" step between the write of a remote index
that un-links a particular object from the index, and the actual deletion of the object, such
that deletions strictly obey the following ordering:
1. Write out index_part.json: this guarantees that any subsequent reader of the metadata will
not try and read the object we unlinked.
2. Call out to control plane to validate that the generation which we use for our attachment is still the latest.
3. If step 2 passes, it is safe to delete the object. Why? The check-in with control plane
together with our visibility rules guarantees that any later generation
will use either the exact `index_part.json` that we uploaded in step 1, or a successor
of it; not an earlier one. In both cases, the `index_part.json` doesn't reference the
key we are deleting anymore, so, the key is invisible to any later attachment generation.
Hence it's safe to delete it.
Note that at step 2 we are only confirming that deletions of objects _no longer referenced
by the specific `index_part.json` written in step 1_ are safe. If we were attempting other deletions concurrently,
these would need their own generation validation step.
If step 2 fails, we may leak the object. This is safe, but has a cost: see [scrubbing](#cleaning-up-orphan-objects-scrubbing). We may avoid this entirely outside of node
failures, if we do proper flushing of deletions on clean shutdown and clean migration.
To avoid doing a huge number of control plane requests to perform generation validation,
validation of many tenants will be done in a single request, and deletions will be queued up
prior to validation: see [Persistent deletion queue](#persistent-deletion-queue) for more.
#### `remote_consistent_lsn` updates
Remote objects are not the only kind of deletion the pageserver does: it also indirectly deletes
WAL data, by feeding back remote_consistent_lsn to safekeepers, as a signal to the safekeepers that
they may drop data below this LSN.
For the same reasons that deletion of objects must be guarded by an attachment generation number
validation step, updates to `remote_consistent_lsn` are subject to the same rules, using
an ordering as follows:
1. upload the index_part that covers data up to LSN `L0` to S3
2. Call out to control plane to validate that the generation which we use for our attachment is still the latest.
3. advance the `remote_consistent_lsn` that we advertise to the safekeepers to `L0`
If step 2 fails, then the `remote_consistent_lsn` advertised
to safekeepers will not advance again until a pageserver
with the latest generation is ready to do so.
**Note:** at step 3 we are not advertising the _latest_ remote_consistent_lsn, we are
advertising the value in the index_part that we uploaded in step 1. This provides
a strong ordering guarantee.
Internally to the pageserver, each timeline will have two remote_consistent_lsn values: the one that
reflects its latest write to remote storage, and the one that reflects the most
recent validation of generation number. It is only the latter value that may
be advertised to the outside world (i.e. to the safekeeper).
The control plane remains unaware of `remote_consistent_lsn`: it only has to validate
the freshness of generation numbers, thereby granting the pageserver permission to
share the information with the safekeeper.
For convenience, in subsequent sections and RFCs we will use "deletion" to mean both deletion
of objects in S3, and updates to the `remote_consistent_lsn`, as updates to the remote consistent
LSN are de-facto deletions done via the safekeeper, and both kinds of deletion are subject to
the same generation validation requirement.
### Pageserver attach/startup changes
#### Attachment
Calls to `/v1/tenant/{tenant_id}/attach` are augmented with an additional
`generation` field in the body.
The pageserver does not persist this: a generation is only good for the lifetime
of a process.
#### Finding the remote indices for timelines
Because index files are now suffixed with generation numbers, the pageserver
cannot always GET the remote index in one request, because it can't always
know a-priori what the latest remote index is.
Typically, the most recent generation to write an index would be our own
generation minus 1. However, this might not be the case: the previous
node might have started and acquired a generation number, and then crashed
before writing out a remote index.
In the general case and as a fallback, the pageserver may list all the `index_part.json`
files for a timeline, sort them by generation, and pick the highest that is `<=`
its current generation for this attachment. The tenant should never load an index
with an attachment generation _newer_ than its own.
These two rules combined ensure that objects written by later generations are never visible to earlier generations.
Note that if a given attachment picks an index part from an earlier generation (say n-2), but crashes & restarts before it writes its own generation's index part, next time it tries to pick an index part there may be an index part from generation n-1.
It would pick the n-1 index part in that case, because it's sorted higher than the previous one from generation n-2.
So, above rules guarantee no determinism in selecting the index part.
are allowed to be attached with stale attachment generations during a multiply-attached
phase in a migration, and in this instance if the old location's pageserver restarts,
it should not try and load the newer generation's index.
To summarize, on starting a timeline, the pageserver will:
1. Issue a GET for index_part.json-<mygeneration-1>
2. If 1 failed, issue a ListObjectsv2 request for index_part.json\* and
pick the newest.
One could optimize this further by using the control plane to record specifically
which generation most recently wrote an index_part.json, if necessary, to increase
the probability of finding the index_part.json in one GET. One could also improve
the chances by having pageservers proactively write out index_part.json after they
get a new generation ID.
#### Re-attachment on startup
On startup, the pageserver will call out to an new control plane `/re-attach`
API (see [Generation API](#generation-api)). This returns a list of
tenants that should be attached to the pageserver, and their generation numbers, which
the control plane will increment before returning.
The pageserver should still scan its local disk on startup, but should _delete_
any local content for tenants not indicated in the `/re-attach` response: their
absence is an implicit detach operation.
**Note** if a tenant is omitted from the re-attach response, its local disk content
will be deleted. This will change in subsequent work, when the control plane gains
the concept of a secondary/standby location: a node with local content may revert
to this status and retain some local content.
#### Cleaning up previous generations' remote indices
Deletion of old indices is not necessary for correctness, although it is necessary
to avoid the ListObjects fallback in the previous section becoming ever more expensive.
Once the new attachment has written out its index_part.json, it may asynchronously clean up historic index_part.json
objects that were found.
We may choose to implement this deletion either as an explicit step after we
write out index_part for the first time in a pageserver's lifetime, or for
simplicity just do it periodically as part of the background scrub (see [scrubbing](#cleaning-up-orphan-objects-scrubbing));
### Control Plane Changes
#### Store generations for attaching tenants
- The `Project` table must store the generation number for use when
attaching the tenant to a new pageserver.
- The `/v1/tenant/:tenant_id/attach` pageserver API will require the generation number,
which the control plane can supply by simply incrementing the `Project`'s
generation number each time the tenant is attached to a different server: the same database
transaction that changes the assigned pageserver should also change the generation number.
#### Generation API
This section describes an API that could be provided directly by the control plane,
or built as a separate microservice. In earlier parts of the RFC, when we
discuss the control plane providing generation numbers, we are referring to this API.
The API endpoints used by the pageserver to acquire and validate generation
numbers are quite simple, and only require access to some persistent and
linerizable storage (such as a database).
Building this into the control plane is proposed as a least-effort option to exploit existing infrastructure and implement generation number issuance in the same transaction that mandates it (i.e., the transaction that updates the `Project` assignment to another pageserver).
However, this is not mandatory: this "Generation Number Issuer" could
be built as a microservice. In practice, we will write such a miniature service
anyway, to enable E2E pageserver/compute testing without control plane.
The endpoints required by pageservers are:
##### `/re-attach`
- Request: `{node_id: <u32>}`
- Response:
- 200 `{tenants: [{id: <TenantId>, gen: <u32>}]}`
- 404: unknown node_id
- (Future: 429: flapping detected, perhaps nodes are fighting for the same node ID,
or perhaps this node was in a retry loop)
- (On unknown tenants, omit tenant from `tenants` array)
- Server behavior: query database for which tenants should be attached to this pageserver.
- for each tenant that should be attached, increment the attachment generation and
include the new generation in the response
- Client behavior:
- for all tenants in the response, activate with the new generation number
- for any local disk content _not_ referenced in the response, act as if we
had been asked to detach it (i.e. delete local files)
**Note** the `node_id` in this request will change in future if we move to ephemeral
node IDs, to be replaced with some correlation ID that helps the control plane realize
if a process is running with the same storage as a previous pageserver process (e.g.
we might use EC instance ID, or we might just write some UUID to the disk the first
- Control plane will see HTTP request timeout, keep re-issuing
request to whoever is the latest attachment point for the tenant
until it succeeds.
- Stale nodes may be trying to execute timeline creation: they will
write out index_part.json files with
stale attachment generation: these will be eventually cleaned up
by the same mechanism as other old indices.
### Unsafe case on badly behaved infrastructure
This section is only relevant if running on a different environment
than EC2 machines with ephemeral disks.
If we ever run pageservers on infrastructure that might transparently restart
a pageserver while leaving an old process running (e.g. a VM gets rescheduled
without the old one being fenced), then there is a risk of corruption, when
the control plane attaches the tenant, as follows:
- If the control plane sends an `/attach` request to node A, then node A dies
and is replaced, and the control plane's retries the request without
incrementing that attachment ID, then it could end up with two physical nodes
both using the same generation number.
- This is not an issue when using EC2 instances with ephemeral storage, as long
as the control plane never re-uses a node ID, but it would need re-examining
if running on different infrastructure.
- To robustly protect against this class of issue, we would either:
- add a "node generation" to distinguish between different processes holding the
same node_id.
- or, dispense with static node_id entirely and issue an ephemeral ID to each
pageserver process when it starts.
## Implementation Part 2: Optimizations
### Persistent deletion queue
Between writing our a new index_part.json that doesn't reference an object,
and executing the deletion, an object passes through a window where it is
only referenced in memory, and could be leaked if the pageserver is stopped
uncleanly. That introduces conflicting incentives: on the one hand, we would
like to delay and batch deletions to
1. minimize the cost of the mandatory validations calls to control plane, and
2. minimize cost for DeleteObjects requests.
On the other hand we would also like to minimize leakage by executing
deletions promptly.
To resolve this, we may make the deletion queue persistent
and then executing these in the background at a later time.
_Note: The deletion queue's reason for existence is optimization rather than correctness,
so there is a lot of flexibility in exactly how the it should work,
as long as it obeys the rule to validate generations before executing deletions,
so the following details are not essential to the overall RFC._
#### Scope
The deletion queue will be global per pageserver, not per-tenant. There
are several reasons for this choice:
- Use the queue as a central point to coalesce validation requests to the
control plane: this avoids individual `Timeline` objects ever touching
the control plane API, and avoids them having to know the rules about
validating deletions. This separation of concerns will avoid burdening
the already many-LoC `Timeline` type with even more responsibility.
- Decouple the deletion queue from Tenant attachment lifetime: we may
"hibernate" an inactive tenant by tearing down its `Tenant`/`Timeline`
objects in the pageserver, without having to wait for deletions to be done.
- Amortize the cost of I/O for the persistent queue, instead of having many
tiny queues.
- Coalesce deletions into a smaller number of larger DeleteObjects calls
Because of the cost of doing I/O for persistence, and the desire to coalesce
generation validation requests across tenants, and coalesce deletions into
larger DeleteObjects requests, there will be one deletion queue per pageserver
rather than one per tenant. This has the added benefit that when deactivating
a tenant, we do not have to drain their deletion queue: deletions can proceed
for a tenant whose main `Tenant` object has been torn down.
#### Flow of deletion
The flow of a deletion is becomes:
1. Need for deletion of an object (=> layer file) is identified.
2. Unlink the object from all the places that reference it (=> `index_part.json`).
3. Enqueue the deletion to a persistent queue.
Each entry is `tenant_id, attachment_generation, S3 key`.
4. Validate & execute in batches:
4.1 For a batch of entries, call into control plane.
4.2 For the subset of entries that passed validation, execute a `DeleteObjects` S3 DELETE request for their S3 keys.
As outlined in the Part 1 on correctness, it is critical that deletions are only
executed once the key is not referenced anywhere in S3.
This property is obviously upheld by the scheme above.
#### We Accept Object Leakage In Acceptable Circumcstances
If we crash in the flow above between (2) and (3), we lose track of unreferenced object.
Further, enqueuing a single to the persistent queue may not be durable immediately to amortize cost of flush to disk.
This is acceptable for now, it can be caught by [the scrubber](#cleaning-up-orphan-objects-scrubbing).
There are various measures we can take to improve this in the future.
1. Cap amount of time until enqueued entry becomes durable (timeout for flush-to-tisk)
2. Proactively flush:
- On graceful shutdown, as we anticipate that some or
all of our attachments may be re-assigned while we are offline.
- On tenant detach.
3. For each entry, keep track of whether it has passed (2).
Only admit entries to (4) one they have passed (2).
This requires re-writing / two queue entries (intent, commit) per deletion.
The important take-away with any of the above is that it's not
disastrous to leak objects in exceptional circumstances.
#### Operations that may skip the queue
Deletions of an entire timeline are [exempt](#Timeline-Deletion) from generation number validation. Once the
control plane sends the deletion request, there is no requirement to retain the readability
of any data within the timeline, and all objects within the timeline path may be deleted
at any time from the control plane's deletion request onwards.
Since deletions of smaller timelines won't have enough objects to compose a full sized
DeleteObjects request, it is still useful to send these through the last part of the
deletion pipeline to coalesce with other executing deletions: to enable this, the
deletion queue should expose two input channels: one for deletions that must be
processed in a generation-aware way, and a fast path for timeline deletions, where
that fast path may skip validation and the persistent queue.
### Cleaning up orphan objects (scrubbing)
An orphan object is any object which is no longer referenced by a running node or by metadata.
Examples of how orphan objects arise:
- A node PUTs a layer object, then crashes before it writes the
index_part.json that references that layer.
- A stale node carries on running for some time, and writes out an unbounded number of
objects while it believes itself to be the rightful writer for a tenant.
- A pageserver crashes between un-linking an object from the index, and persisting
the object to its deletion queue.
Orphan objects are functionally harmless, but have a small cost due to S3 capacity consumed. We
may clean them up at some time in the future, but doing a ListObjectsv2 operation and cross
referencing with the latest metadata to identify objects which are not referenced.
Scrubbing will be done only by an attached pageserver (not some third party process), and deletions requested during scrub will go through the same
validation as all other deletions: the attachment generation must be
fresh. This avoids the possibility of a stale pageserver incorrectly
thinking than an object written by a newer generation is stale, and deleting
it.
It is not strictly necessary that scrubbing be done by an attached
pageserver: it could also be done externally. However, an external
scrubber would still require the same validation procedure that
a pageserver's deletion queue performs, before actually erasing
objects.
## Operational impact
### Availability
Coordination of generation numbers via the control plane introduce a dependency for certain
operations:
1. Starting new pageservers (or activating pageservers after a restart)
2. Executing enqueued deletions
3. Advertising updated `remote_consistent_lsn` to enable WAL trimming
Item 1. would mean that some in-place restarts that previously would have resumed service even if the control plane were
unavailable, will now not resume service to users until the control plane is available. We could
avoid this by having a timeout on communication with the control plane, and after some timeout,
resume service with the previous generation numbers (assuming this was persisted to disk). However,
this is unlikely to be needed as the control plane is already an essential & highly available component. Also, having a node re-use an old generation number would complicate
reasoning about the system, as it would break the invariant that a generation number uniquely identifies
a tenant's attachment to a given pageserver _process_: it would merely identify the tenant's attachment
to the pageserver _machine_ or its _on-disk-state_.
Item 2. is a non-issue operationally: it's harmless to delay deletions, the only impact of objects pending deletion is
the S3 capacity cost.
Item 3. could be an issue if safekeepers are low on disk space and the control plane is unavailable for a long time. If this became an issue,
we could adjust the safekeeper to delete segments from local disk sooner, as soon as they're uploaded to S3, rather than waiting for
remote_consistent_lsn to advance.
For a managed service, the general approach should be to make sure we are monitoring & respond fast enough
that control plane outages are bounded in time.
There is also the fact that control plane runs in a single region.
The latency for distant regions is not a big concern for us because all request types added by this RFC are either infrequent or not in the way of the data path.
However, we lose region isolation for the operations listed above.
The ongoing work to split console and control will give us per-region control plane, and all operations in this RFC can be handled by these per-region control planes.
With that in mind, we accept the trade-offs outlined in this paragraph.
We will also implement an "escape hatch" config generation numbers, where in a major disaster outage,
we may manually run pageservers with a hand-selected generation number, so that we can bring them online
independently of a control plane.
### Rollout
Although there is coupling between components, we may deploy most of the new data plane components
independently of the control plane: initially they can just use a static generation number.
#### Phase 1
The pageserver is deployed with some special config to:
- Always act like everything is generation 1 and do not wait for a control plane issued generation on attach
- Skip the places in deletion and remote_consistent_lsn updates where we would call into control plane
#### Phase 2
The control plane changes are deployed: control plane will now track and increment generation numbers.
#### Phase 3
The pageserver is deployed with its control-plane-dependent changes enabled: it will now require
the control plane to service re-attach requests on startup, and handle generation
validation requests.
### On-disk backward compatibility
Backward compatibility with existing data is straightforward:
- When reading the index, we may assume that any layer whose metadata doesn't include
generations will have a path without generation suffix.
- When locating the index file on attachment, we may use the "fallback" listing path
and if there is only an index without generation suffix, that is the one we load.
It is not necessary to re-write existing layers: even new index files will be able
to represent generation-less layers.
### On-disk forward compatibility
We will do a two phase rollout, probably over multiple releases because we will naturally
have some of the read-side code ready before the overall functionality is ready:
1. Deploy pageservers which understand the new index format and generation suffixes
in keys, but do not write objects with generation numbers in the keys.
2. Deploy pageservers that write objects with generation numbers in the keys.
Old pageservers will be oblivious to generation numbers. That means that they can't
read objects with generation numbers in the name. This is why we must
first step must deploy the ability to read, before the second step
starts writing them.
# Frequently Asked Questions
## Why a generation _suffix_ rather than _prefix_?
The choice is motivated by object listing, since one can list by prefix but not
suffix.
In [finding remote indices](#finding-the-remote-indices-for-timelines), we rely
on being able to do a prefix listing for `<tenant>/<timeline>/index_part.json*`.
That relies on the prefix listing.
The converse case of using a generation prefix and listing by generation is
not needed: one could imagine listing by generation while scrubbing (so that
a particular generation's layers could be scrubbed), but this is not part
of normal operations, and the [scrubber](#cleaning-up-orphan-objects-scrubbing) probably won't work that way anyway.
## Wouldn't it be simpler to have a separate deletion queue per timeline?
Functionally speaking, we could. That's how RemoteTimelineClient currently works,
but this approach does not map well to a long-lived persistent queue with
generation validation.
Anything we do per-timeline generates tiny random I/O, on a pageserver with
tens of thousands of timelines operating: to be ready for high scale, we should:
- A) Amortize costs where we can (e.g. a shared deletion queue)
- B) Expect to put tenants into a quiescent state while they're not
busy: i.e. we shouldn't keep a tenant alive to service its deletion queue.
This was discussed in the [scope](#scope) part of the deletion queue section.
# Appendix A: Examples of use in high availability/failover
The generation numbers proposed in this RFC are adaptable to a variety of different
failover scenarios and models. The sections below sketch how they would work in practice.
### In-place restart of a pageserver
"In-place" here means that the restart is done before any other element in the system
has taken action in response to the node being down.
- After restart, the node issues a re-attach request to the control plane, and
receives new generation numbers for all its attached tenants.
- Tenants may be activated with the generation number in the re-attach response.
- If any of its attachments were in fact stale (i.e. had be reassigned to another
node while this node was offline), then
- the re-attach response will inform the tenant about this by not including
the tenant of this by _not_ incrementing the generation for that attachment.
- This will implicitly block deletions in the tenant, but as an optimization
the pageserver should also proactively stop doing S3 uploads when it notices this stale-generation state.
- The control plane is expected to eventually detach this tenant from the
pageserver.
If the control plane does not include a tenant in the re-attach response,
but there is still local state for the tenant in the filesystem, the pageserver
deletes the local state in response and does not load/active the tenant.
See the [earlier section on pageserver startup](#pageserver-attachstartup-changes) for details.
Control plane can use this mechanism to clean up a pageserver that has been
down for so long that all its tenants were migrated away before it came back
up again and asked for re-attach.
### Failure of a pageserver
In this context, read "failure" as the most ambiguous possible case, where
a pageserver is unavailable to clients and control plane, but may still be executing and talking
to S3.
#### Case A: re-attachment to other nodes
1. Let's say node 0 becomes unresponsive in a cluster of three nodes 0, 1, 2.
2. Some external mechanism notices that the node is unavailable and initiates
movement of all tenants attached to that node to a different node according
to some distribution rule.
In this example, it would mean incrementing the generation
of all tenants that were attached to node 0, as each tenant's assigned pageserver changes.
3. A tenant which is now attached to node 1 will _also_ still be attached to node
0, from the perspective of node 0. Node 0 will still be using its old generation,
node 1 will be using a newer generation.
4. S3 writes will continue from nodes 0 and 1: there will be an index_part.json-00000001
\_and\* an index_part.json-00000002. Objects written under the old suffix
after the new attachment was created do not matter from the rest of the system's
perspective: the endpoints are reading from the new attachment location. Objects
written by node 0 are just garbage that can be cleaned up at leisure. Node 0 will
not do any deletions because it can't synchronize with control plane, or if it could,
its deletion queue processing would get errors for the validation requests.
#### Case B: direct node replacement with same node_id and drive
This is the scenario we would experience if running pageservers in some dynamic
VM/container environment that would auto-replace a given node_id when it became
unresponsive, with the node's storage supplied by some network block device
that is attached to the replacement VM/container.
1. Let's say node 0 fails, and there may be some other peers but they aren't relevant.
2. Some external mechanism notices that the node is unavailable, and creates
a "new node 0" (Node 0b) which is a physically separate server. The original node 0
(Node 0a) may still be running, because we do not assume the environment fences nodes.
3. On startup, node 0b re-attaches and gets higher generation numbers for
all tenants.
4. S3 writes continue from nodes 0a and 0b, but the writes do not collide due to different
generation in the suffix, and the writes from node 0a are not visible to the rest
of the system because endpoints are reading only from node 0b.
# Appendix B: interoperability with other features
## Sharded Keyspace
The design in this RFC maps neatly to a sharded keyspace design where subsets of the key space
for a tenant are assigned to different pageservers:
- the "unit of work" for attachments becomes something like a TenantShard rather than a Tenant
- TenantShards get generation numbers just as Tenants do.
- Write workload (ingest, compaction) for a tenant is spread out across pageservers via
TenantShards, but each TenantShard still has exactly one valid writer at a time.
## Read replicas
_This section is about a passive reader of S3 pageserver state, not a postgres
read replica_
For historical reads to LSNs below the remote persistent LSN, any node may act as a reader at any
time: remote data is logically immutable data, and the use of deferred deletion in this RFC helps
mitigate the fact that remote data is not _physically_ immutable (i.e. the actual data for a given
page moves around as compaction happens).
A read replica needs to be aware of generations in remote data in order to read the latest
metadata (find the index_part.json with the latest suffix). It may either query this
from the control plane, or find it with ListObjectsv2 request
## Seamless migration
To make tenant migration totally seamless, we will probably want to intentionally double-attach
a tenant briefly, serving reads from the old node while waiting for the new node to be ready.
This RFC enables that double-attachment: two nodes may be attached at the same time, with the migration destination
having a higher generation number. The old node will be able to ingest and serve reads, but not
do any deletes. The new node's attachment must also avoid deleting layers that the old node may
still use. A new piece of state
will be needed for this in the control plane's definition of an attachment.
## Warm secondary locations
To enable faster tenant movement after a pageserver is lost, we will probably want to spend some
disk capacity on keeping standby locations populated with local disk data.
There's no conflict between this RFC and that: implementing warm secondary locations on a per-tenant basis
would be a separate change to the control plane to store standby location(s) for a tenant. Because
the standbys do not write to S3, they do not need to be assigned generation numbers. When a tenant is
re-attached to a standby location, that would increment the tenant attachment generation and this
would work the same as any other attachment change, but with a warm cache.
## Ephemeral node IDs
This RFC intentionally avoids changing anything fundamental about how pageservers are identified
and registered with the control plane, to avoid coupling the implementation of pageserver split
brain protection with more fundamental changes in the management of the pageservers.
Moving to ephemeral node IDs would provide an extra layer of
resilience in the system, as it would prevent the control plane
accidentally attaching to two physical nodes with the same
generation, if somehow there were two physical nodes with
the same node IDs (currently we rely on EC2 guarantees to
eliminate this scenario). With ephemeral node IDs, there would be
no possibility of that happening, no matter the behavior of
underlying infrastructure.
Nothing fundamental in the pageserver's handling of generations needs to change to handle ephemeral node IDs, since we hardly use the
`node_id` anywhere. The `/re-attach` API would be extended
to enable the pageserver to obtain its ephemeral ID, and provide
some correlation identifier (e.g. EC instance ID), to help the
control plane re-attach tenants to the same physical server that
This is a copy from the [original Notion page](https://www.notion.so/neondatabase/Proposal-Pageserver-MVCC-S3-Storage-8a424c0c7ec5459e89d3e3f00e87657c?pvs=4), taken on 2023-08-16.
This is for archival mostly.
The RFC that we're likely to go with is https://github.com/neondatabase/neon/pull/4919.
---
# Proposal: Pageserver MVCC S3 Storage
tl;dr: this proposal enables Control Plane to attach a tenant to a new pageserver without being 100% certain that it has been detached from the old pageserver. This enables us to automate failover if a pageserver dies (no human in the loop).
# Problem Statement
The current Neon architecture requires the Control Plane to guarantee that a tenant is only attached to one pageserver at a time. If a tenant is attached to multiple pageservers simultaneously, the pageservers will overwrite each other’s changes in S3 for that tenant, resulting in data loss for that tenant.
The above imposes limitations on tenant relocation and future designs for high availability. For instance, Control Plane cannot relocate a tenant to another pageserver before it is 100% certain that the tenant is detached from the source pageserver. If the source pageserver is unresponsive, the tenant detach procedure cannot proceed, and Control Plane has no choice but to wait for either the source to become responsive again, or rely on a node failure detection mechanism to detect that the source pageserver is dead, and give permission to skip the detachment step. Either way, the tenant is unavailable for an extended period, and we have no means to improve it in the current architecture.
Note that there is no 100% correct node failure detection mechanism, and even techniques to accelerate failure detection, such as ********************************shoot-the-other-node-in-the-head,******************************** have their limits. So, we currently rely on humans as node failure detectors: they get alerted via PagerDuty, assess the situation under high stress, and make the decision. If they make the wrong call, or the apparent dead pageserver somehow resurrects later, we’ll have data loss.
Also, by relying on humans, we’re [incurring needless unscalable toil](https://sre.google/sre-book/eliminating-toil/): as Neon grows, pageserver failures will become more and more frequent because our fleet grows. Each instance will need quick response time to minimize downtime for the affected tenants, which implies higher toil, higher resulting attrition, and/or higher personnel cost.
Lastly, there are foreseeable needs by operation and product such as zero-downtime relocation and automatic failover/HA. For such features, the ability to have a tenant purposefully or accidentally attached to more than one pageserver will greatly reduce risk of data loss, and improve availability.
# High-Level Idea
The core idea is to evolve the per-Tenant S3 state to an MVCC-like scheme, allowing multiple pageservers to operate on the same tenant S3 state without interference. To make changes to S3, pageservers acquire long-running transactions from Control Plane. After opening a transaction, Pageservers make PUTs directly against S3, but they keys include the transaction ID, so overwrites never happen. Periodically, pageservers talk back to Control Plane to commit their transaction. This is where Control Plane enforces strict linearizability, favoring availability over work-conservation: commit is only granted if no transaction started after the one that’s requesting commit. Garbage collection is done through deadlists, and it’s simplified tremendously by above commit grant/reject policy.
Minimal changes are required for safekeepers to allow WAL for a single timeline be consumed by more than one pageserver without premature truncation.
**Above scheme makes it safe to attach tenants without a 100% correct node failure detection mechanism. Further, it makes it safe to interleave tenant-attachment to pageservers, unlocking new capabilities for (internal) product features:**
- **Fast, Zero-Toil Failover on Network Partitions or Instance Failure**: if a pageserver is not reachable (network partition, hardware failure, overload) we want to spread its attached tenants to new pageservers to restore availability, within the range of *seconds*. We cannot afford gracious timeouts to maximize the probability that the unreachable pageserver has ceased writing to S3. This proposal enables us to attach the tenants to the replacement pageservers, and redirect their computes, without having to wait for confirmation that the unreachable pageserver has ceased writing to S3.
- **************************************Zero-Downtime Relocation:************************************** we want to be able to relocate tenants to different pageservers with minimized availability or a latency impact. This proposal enables us to attach the relocating Tenant to the destination Pageserver before detaching it from the source Pageserver. This can help minimize downtime because we can wait for the destination to catch up on WAL processing before redirecting Computes.
# Design
The core idea is to evolve the per-Tenant S3 state to a per-tenant MVCC-like scheme.
To make S3 changes for a given tenant, Pageserver requests a transaction ID from control plane for that tenant. Without a transaction ID, Pageserver does not write to S3.
Once Pageserver received a transaction ID it is allowed to produce new objects and overwrite objects created in this transaction. Pageserver is not allowed to delete any objects; instead, it marks the object as deleted by appending the key to the transaction’s deadlist for later deletion. Commits of transactions are serialized through Control Plane: when Pageserver wants to commit a transaction, it sends an RPC to Control Plane. Control Plane responds with a commit grant or commit reject message. Commit grant means that the transaction’s changes are now visible to subsequent transactions. Commit reject means that the transaction’s changes are not and never will be visible to another Pageserver instance, and the rejected Pageserver is to cease further activity on that tenant.
For the purposes of Pageserver, we want **linearizability** of a tenant’s S3 state. Since our transactions are scoped per tenant, it is sufficient for linearizability to grant commit if and only if no other transaction has been started since the commit-requesting transaction started.
For example, consider the case of a single tenant, attached to Pageserver A. Pageserver A has an open transaction but becomes unresponsive. Control Plane decides to relocate the tenant to another Pageserver B. It need *not* wait for A to be 100%-certainly down before B can start uploading to S3 for that tenant. Instead, B can start a new transaction right away, make progress, and get commit grants; What about A? The transaction is RejectPending in Control Plane until A eventually becomes responsive again, tries to commit, gets a rejection, acknowledges it, and thus its transaction becomes RejectAcknowledge. If A is definitively dead, operator can also force-transition from state RejectPending to RejectAcknowledged. But critically, Control Plane doesn’t have for A’s transaction to become RejectAcknowledge before attaching the tenant to B.
```mermaid
sequenceDiagram
participant CP
participant A
participant S3
participant B
CP -->> A: attach tenant
activate A
A -->> CP: start txn
CP -->> A: txn=23, last_committed_txn=22
Note over CP,A: network partition
CP --x A: heartbeat
CP --x A: heartbeat
Note over CP: relocate tenant to avoid downtime
CP -->> B: attach tenant
activate B
B -->> CP: start txn
Note over CP: mark A's txn 23 as RejectPending
CP -->> B: txn=24, last-committed txn is 22
B -->> S3: PUT X.layer.24<br>PUT index_part.json.24 referencing X.layer.24
B -->> CP: request commit
CP -->> B: granted
B -->> CP: start txn
CP -->> B: txn=25, last_committed_txn=22
A -->> S3: PUT Y.layer.23 <br> PUT index_part.json.23 referencing Y.layer.23
A --x CP: request commit
A --x CP: request commit
Note over CP,A: partition is over
A -->> CP: request commit
Note over CP: most recently started txn is 25, not 23, reject
CP -->> A: reject
A -->> CP: acknowledge reject
Note over CP: mark A's txn 23 as RejectAcknowledged
deactivate A
B -->> S3: PUT 000-FFF_X-Y.layer.**************25**************<br>...
deactivate B
```
If a Pageserver gets a rejection to a commit request, it acknowledges rejection and cedes further S3 uploads for the tenant, until it receives a `/detach` request for the tenant (control plane has most likely attached the tenant to another pageserver in the meantime).
In practice, Control Plane will probably extend the commit grant/reject schema above, taking into account the pageserver to which it last attached the tenant. In the above example, Control Plane could remember that the pageserver that is supposed to host the tenant is pageserver B, and reject start-txn and commit requests from pageserver A. It would also use such requests from A as a signal that A is reachable again, and retry the `/detach` .
<aside>
💡 A commit failure causes the tenant to become effectively `Broken`. Pageserver should persist this locally so it doesn’t bother ControlPlane for a new txn when Pageserver is restarted.
We mentioned earlier that once a transaction commits, its changes are visible to subsequent transactions. But how does a given transaction know where to look for the data? There is no longer a single `index_part.json` per timeline, or a single `timelines/:timeline_id` prefix to look for; they’re all multi-versioned, suffixed by the txn number.
The solution is: at transaction start, Pageserver receives the last-committed transaction ID from Control Plane (`last_committed_txn` in the diagram). last_commited_txn is the upper bound for what is visible for the current transaction. Control Plane keeps track of each open transaction’s last_committed_txn for purposes of garbage collection (see later paragraph).
Equipped with last_committed_txn, Pageserver then discovers
- the current index part of a timeline at `tenants/:tenant_id/timelines/:timeline_id/index_part.json.$last_committed_txn`. The `index_part.json.$last_committed_txn` has the exact same contents as the current architecture’s index_part.json, i.e. full list of layers.
- the list of existent timelines as part of the `attach` RPC from CP;
There is no other S3 state per tenant, so, that’s all the visibility required.
An alternative to receiving the list of existent timelines from CP is to introduce a proper **********SetOfTimelines********** object in S3, and multi-version it just like above. For example, we could have a `tenants/:tenant_id/timelines.json.$txn` file that references `index_part.json.$last_committed_txn` . It can be added later if more separation between CP and PS is desired.
So, the only MVCC’ed object types in this proposal are LayerFile and IndexPart (=individual timeline), but not the SetOfTimelines in a given tenant. Is this a problem? For example, the Pageserver’s garbage collection code needs to know the full set of timelines of a tenant. Otherwise it’ll make incorrect decisions. What if Pageserver A knows about timelines {R,S}, but another Pageserver B created an additional branch T, so, its set of timelines is {R,S,T}. Both pageservers will run GC code, and so, PS A may decide to delete a layer that’s still needed for branch T. Not a problem with this propsoal, because the effect of GC (i.e., layer deletion) is properly MVCC’ed.
## Longevity Of Transactions & Availability
Pageserver depends on Control Plane to start a new transaction. If ControlPlane is down, no new transactions can be started.
Pageservers commit transactions based on a maximum amount of uncommitted changes that have accumulated in S3. A lower maximum increases dependence and load on ControlPlane which decreases availability. A higher maximum risks losing more work in the event of failover; the work will have to be re-done in a new transaction on the new node.
Pageservers are persist the open txn id in local storage, so that they can resume the transaction after restart, without dependence on Control Plane.
## **Operations**
********PUTs:********
- **layer files**
- current architecture: layer files are supposed to be write-once, but actually, there are edge-cases where we PUT the same layer file name twice; namely if we PUT the file to S3 but crash before uploading the index part that references it; then detach + attach, and re-run compaction, which is non-deterministic.
- this proposal: with transactions, we can now upload layers and index_part.json concurrently, just need to make sure layer file upload is done before we request txn commit.
- **index part** upload: `index_part.json.$txn` may be created and subsequently overwritten multiple times in a transaction; it is an availability/work-loss trade-off how often to request a commit from CP.
**************DELETEs**************: for deletion, we maintain a deadlist per transaction. It is located at `tenants/:tenant_id/deadlist/deadlist.json.$txn`. It is PUT once before the pageserver requests requests commit, and not changed after sending request to commit. An object created in the current txn need not (but can) be on the deadlist — it can be DELETEd immediately because it’s not visible to other transactions. An example use case would be an L0 layer that gets compacted within one transaction; or, if we ever start MVCC’ing the set of timelines of a tenant, a short-lived branch that is created & destroyed within one transaction.
<aside>
☝ **Deadlist Invariant:** if a an object is on a deadlist of transaction T, it is not referenced from anywhere else in the full state visible to T or any later started transaction > T.
</aside>
### Rationale For Deadlist.json
Given that this proposal only MVCC’s layers and indexparts, one may ask why the deadlist isn’t part of indexpart. The reason is to not lose generality: the deadlist is just a list of keys; it is not necessary to understand the data format of the versioned object to process the deadlist. This is important for garbage collection / vacuuming, which we’ll come to in the next section.
## Garbage Collection / Vacuuming
After a transaction has reached reject-acknowledged state, Control Plane initiates a garbage collection procedure for the aborted transaction.
Control Plane is in the unique position about transaction states. Here is a sketch of the exact transaction states and what Control Plane keeps track of.
```
struct Tenant {
...
txns: HashMap<TxnId, Transaction>,
// the most recently started txn's id; only most recently sarted can win
next_winner_txn: Option<TxnId>,
}
struct Transaction {
id: TxnId, // immutable
last_committed_txn: TxnId, // immutable; the most recent txn in state `Committed`
// when self was started
pageserver_id: PageserverId,
state: enum {
Open,
Committed,
RejectPending,
RejectAcknowledged, // invariant: we know all S3 activity has ceded
GarbageCollected,
}
}
```
Object creations & deletions by a rejected transaction have never been visible to other transactions. That is true for both RejectPending and RejectAcknowledged states. The difference is that, in RejectPending, the pageserver may still be uploading to S3, whereas in RejectAcknowledged, Control Plane can be certain that all S3 activity in the name of that transaction has ceded. So, once a transaction reaches state RejectAcknowledged state, it is safe to DELETE all objects created by that transaction, and discard the transaction’s deadlists.
A transaction T in state Committed has subsequent transactions that may or may not reference the objects it created. None of the subsequent transaction can reference the objects on T’s deadlist, though, as per the Deadlist Invariant (see previous section).
So, for garbage collection, we need to assess transactions in state Committed and RejectAcknowledged:
- Commited: delete objects on the deadlist.
- We don’t need a LIST request here, the deadlist is sufficient. So, it’s really cheap.
- This is **not true MVCC garbage collection**; by deleting the objects on Committed transaction T ’s deadlist, we might delete data referenced by other transactions that were concurrent with T, i.e., they started while T was still open. However, the fact that T is committed means that the other transactions are RejectPending or RejectAcknowledged, so, they don’t matter. Pageservers executing these doomed RejectPending transactions must handle 404 for GETs gracefully, e.g., by trying to commit txn so they observe the rejection they’re destined to get anyways. 404’s for RejectAcknowledged is handled below.
- RejectAcknowledged: delete all objects created in that txn, and discard deadlists.
- 404s / object-already-deleted type messages must be expected because of Committed garbage collection (see above)
- How to get this list of objects created in a txn? Open but solvable design question; Ideas:
- **Brute force**: within tenant prefix, search for all keys ending in `.$txn` and delete them.
- **WAL for PUTs**: before a txn PUTs an object, it logs to S3, or some other equivalently durable storage, that it’s going to do it. If we log to S3, this means we have to do an additional WAL PUT per “readl” PUT.
- ******************************LIST with reorg’ed S3 layout (preferred one right now):****************************** layout S3 key space such that `$txn` comes first, i.e., `tenants/:tenant_id/$txn/timelines/:timeline_id/*.json.$txn` . That way, when we need to GC a RejectAcknowledged txn, we just LIST the entire `tenants/:tenant_id/$txn` prefix and delete it. The cost of GC for RejectAcknowledged transactions is thus proportional to the number of objects created in that transaction.
## Branches
This proposal only MVCC’s layer files and and index_part.json, but leaves the tenant object not-MVCCed. We argued earlier that it’s fine to ignore this for now, because
1. Control Plane can act as source-of-truth for the set of timelines, and
2. The only operation that makes decision based on “set of timelines” is GC, which in turn only does layer deletions, and layer deletions ***are*** properly MVCC’ed.
Now that we’ve introduced garbage collection, let’s elaborate a little more on (2). Recall our example from earlier: Pageserver A knows about timelines {R,S}, but another Pageserver B created an additional branch T, so, its set of timelines is {R,S,T}. Both pageservers will run GC code, and so, PS A may decide to delete a layer that’s still needed for branch T.
How does the MVCC’ing of layer files protect us here? If A decides to delete that layer, it’s just on A’s transaction’s deadlist, but still present in S3 and usable by B. If A commits first, B won’t be able to commit and the layers in timeline T will be vacuumed. If B commits first, A’s deadlist is discarded and the layer continues to exist.
## Safekeeper Changes
We need to teach the safekeepers that there can be multiple pageservers requesting WAL for the same timeline, in order to prevent premature WAL truncation.
In the current architecture, the Safekeeper service currently assumes only one Pageserver and is allowed to prune WAL older than that Pageserver’s `remote_consistent_lsn`. Safekeeper currently learns the `remote_consistent_lsn` through the walreceiver protocol.
So, if we have a tenant attached to two pageservers at the same time, they will both try to stream WAL and the Safekeeper will get confused about which connection’s `remote_consistent_lsn` to use as a basis for WAL pruning.
What do we need to change to make it work? We need to make sure that the Safekeepers only prune WAL up to the `remote_consistent_lsn` of the last-committed transaction.
The straight-forward way to get it is to re-design WAL pruning as follows:
1. Pageserver reports remote_consistent_lsn as part of transaction commit to Control Plane.
2. Control Plane makes sure transaction state update is persisted.
3. Control Plane (asynchronous to transaction commit) reconciles with Safekeepers to ensure WAL pruning happens.
The above requires non-trivial changes, but, in the light of other planned projects such as restore-tenant-from-safekeeper-wal-backups, I think Control Plane will need to get involved in WAL pruning anyways.
# How This Proposal Unlocks Future Features
Let us revisit the example from the introduction where we were thinking about handling network partitions. Network partitions need to be solved first, because they’re unavoidable in distributed systems. We did that. Now let’s see how we can solve actual product problems:
## **Fast, Zero-Toil Failover on Network Partitions or Instance Failure**
The “Problem Statement” section outlined the current architecture’s problems with regards to network partitions or instance failure: it requires a 100% correct node-dead detector to make decisions, which doesn’t exist in reality. We rely instead on human toil: an oncall engineer has to inspect the situation and make a decision, which may be incorrect and in any case take time in the order of minutes, which means equivalent downtime for users.
With this proposal, automatic failover for pageservers is trivial:
If a pageserver is unresponsive from Control Plane’s / Compute’s perspective, Control Plane does the following:
- attach all tenants of the unresponsive pageserver to new pageservers
- switch over these tenants’ computes immediately;
At this point, availability is restored and user pain relieved.
What’s left is to somehow close the doomed transaction of the unresponsive pageserver, so that it beomes RejectAcknowledged, and GC can make progress. Since S3 is cheap, we can afford to wait a really long time here, especially if we put a soft bound on the amount of data a transaction may produce before it must commit. Procedure:
1. Ensure the unresponsive pageserver is taken out of rotation for new attachments. That probably should happen as part of the routine above.
2. Make a human operator investigate decide what to do (next morning, NO ONCALL ALERT):
1. Inspect the instance, investigate logs, understand root cause.
2. Try to re-establish connectivity between pageserver and Control Plane so that pageserver can retry commits, get rejected, ack rejection ⇒ enable GC.
3. Use below procedure to decomission pageserver.
### Decomissioning A Pageserver (Dead or Alive-but-Unrespsonive)
The solution, enabled by this proposal:
1. Ensure that pageserver’s S3 credentials are revoked so that it cannot make new uploads, which wouldn’t be tracked anywhere.
2. Let enough time pass for the S3 credential revocation to propagate. Amazon doesn’t give a guarantee here. As stated earlier, we can easily afford to wait here.
3. Mark all Open and RejectPending transactions of that pageserver as RejectAcknowledge.
Revocation of the S3 credentials is required so that, once we transition all the transactions of that pageserver to RejectAcknowledge, once garbage-collection pass is guaranteed to delete all objects that will ever exist for that pageserver. That way, we need not check *****GarbageCollected***** transactions every again.
## Workflow: Zero-Downtime Relocation
With zero-downtime relocation, the goal is to have the target pageserver warmed up, i.e., at the same `last_record_lsn` as the source pageserver, before switching over Computes from source to target pageserver.
With this proposal, it works like so:
1. Grant source pageserver its last open transaction. This one is doomed to be rejected later, unless the relocation fails.
2. Grant target pageserver its first open transaction.
3. Have target pageserver catch up on WAL, streaming from last-committed-txn’s remote_consistent_lsn onwards.
4. Once target pageserver reports `last_record_lsn` close enough to source pageserver, target pageserver requests commit.
5. Drain compute traffic from source to target pageserver. (Source can still answer requests until it tries to commit and gets reject, so, this will be quite smooth).
Note that as soon as we complete step (4), the source pageserver’s transaction is doomed to be rejected later. Conversely, if the target can’t catch up fast enough, the source will make a transaction commit earlier. This will generally happen if there is a lot of write traffic coming in. The design space to make thing smooth here is large, but well explored in other areas of computing, e.g., VM live migration. We have all the important policy levers at hand, e.g.,
- delaying source commits if we see target making progress
- slowing down source consumption (need some signalling mechanism for it)
- slowing down compute wal generation
- …
It doesn’t really matter, what’s important is that two pageservers can overlap.
# Additional Trade-Offs / Remarks Brought Up During Peer Review
This proposal was read by and discussed @Stas and @Dmitry Rodionov prior to publishing it with the broader team. (This does not mean they endorse this proposal!).
Issues that we discussed:
1.**Frequency of transactions:** If even idle tenants commit every 10min or so, that’s quite a lot of load on Control Plane. Can we minimize it by Equating Transaction Commit Period to Attachment Period? I.e. start txn on attach, commit on detach?
1. Would be nice, but, if a tenant is attached for 1 month, then PS dies, we lose 1 month of work.
2. ⇒ my solution to this problem: Adjusted this proposal to make transaction commit frequency proportional to amount of uncommitted data.
1. It’s ok to spend resources on active users, they pay us money to do it!
2. The amount of work per transaction is minimal.
1. In current Control Plane, it’s a small database transaction that is super unlikely to conflict with other transactions.
2. I have very little concerns about scalability of the commit workload on CP side because it's trivially horizontally scalable by sharding by tenant.
3. There's no super stringent availability requirement on control plane; if a txn can't commit because it can't reach the CP, PS can continue & retry in the background, speculating that it's CP downtime and not PS-partitioned-off scenario.
4. Without stringent availability requirement, there's flexibility for future changes to CP-side-implementation.
2.************************************************Does this proposal address mirroring / no-performance-degradation failover ?************************************************
1. No it doesn’t. It only provides the building block for attaching a tenant to a new pageserver without having to worry that the tenant is detached on the old pageserver.
2. A simple scheme to build no-performance-degradation failover on top of this proposal is to have an asynchronous read-only replica of a tenant on another pageserver in the same region.
3. Another more ambitious scheme to get no-performance-degradation would be [One-Pager: Layer File Spreading (Christian)](https://www.notion.so/One-Pager-Layer-File-Spreading-Christian-eb6b64182a214e11b3fceceee688d843?pvs=21); this proposal would be used in layer file spreading for risk-free automation of TenantLeader failover, which hasn’t been addressed Ithere.
4. In any way, failover would restart from an older S3 state, and need to re-ingest WAL before being able to server recently written pages.
1. Is that a show-stopper? I think not.
2. Is it suboptimal? Absolutely: if a pageserver instance fails, all its tenants will be distributed among the remaining pageservers (OK), and all these tenants will ask the safekeepers for WAL at the same time (BAD). So, pageserver instance failure will cause a load spike in safekeepers.
1. Personally I think that’s an OK trade-off to make.
2. There are countless options to avoid / mitigate the load spike. E.g., pro-actively streaming WAL to the standby read-only replica.
3.********************************************Does this proposal allow multiple writers for a tenant?********************************************
1. In abstract terms, this proposal provides a linearized history for a given S3 prefix.
2. In concrete terms, this proposal provides a linearized history per tenant.
3. There can be multiple writers at a given time, but only one of them will win to become part of the linearized history.
4.************************************************************************************Alternative ideas mentioned during meetings that should be turned into a written prospoal like this one:************************************************************************************
1.@Dmitry Rodionov : having linearized storage of index_part.json in some database that allows serializable transactions / atomic compare-and-swap PUT
2.@Dmitry Rodionov :
3.@Stas : something like this scheme, but somehow find a way to equate attachment duration with transaction duration, without losing work if pageserver dies months after attachment.
# Crash-Consistent Layer Map Updates By Leveraging `index_part.json`
* Created on: Aug 23, 2023
* Author: Christian Schwarz
## Summary
This RFC describes a simple scheme to make layer map updates crash consistent by leveraging the `index_part.json` in remote storage.
Without such a mechanism, crashes can induce certain edge cases in which broadly held assumptions about system invariants don't hold.
## Motivation
### Background
We can currently easily make complex, atomic updates to the layer map by means of an RwLock.
If we crash or restart pageserver, we reconstruct the layer map from:
1. local timeline directory contents
2. remote `index_part.json` contents.
The function that is responsible for this is called `Timeline::load_layer_map()`.
The reconciliation process's behavior is the following:
* local-only files will become part of the layer map as local-only layers and rescheduled for upload
* For a file name that, by its name, is present locally and in the remote `index_part.json`, but where the local file has a different size (future: checksum) than the remote file, we will delete the local file and leave the remote file as a `RemoteLayer` in the layer map.
### The Problem
There are are cases where we need to make an atomic update to the layer map that involves **more than one layer**.
The best example is compaction, where we need to insert the L1 layers generated from the L0 layers, and remove the L0 layers.
As stated above, making the update to the layer map in atomic way is trivial.
But, there is no system call API to make an atomic update to a directory that involves more than one file rename and deletion.
Currently, we issue the system calls one by one and hope we don't crash.
What happens if we crash and restart in the middle of that system call sequence?
We will reconstruct the layer map according to the reconciliation process, taking as input whatever transitory state the timeline directory ended up in.
We cannot roll back or complete the timeline directory update during which we crashed, because we keep no record of the changes we plan to make.
### Problem's Implications For Compaction
The implications of the above are primarily problematic for compaction.
Specifically, the part of it that compacts L0 layers into L1 layers.
Remember that compaction takes a set of L0 layers and reshuffles the delta records in them into L1 layer files.
Once the L1 layer files are written to disk, it atomically removes the L0 layers from the layer map and adds the L1 layers to the layer map.
It then deletes the L0 layers locally, and schedules an upload of the L1 layers and and updated index part.
If we crash before deleting L0s, but after writing out L1s, the next compaction after restart will re-digest the L0s and produce new L1s.
This means the compaction after restart will **overwrite** the previously written L1s.
Currently we also schedule an S3 upload of the overwritten L1.
If the compaction algorithm doesn't change between the two compaction runs, is deterministic, and uses the same set of L0s as input, then the second run will produce identical L1s and the overwrites will go unnoticed.
*However*:
1. the file size of the overwritten L1s may not be identical, and
2. the bit pattern of the overwritten L1s may not be identical, and,
3. in the future, we may want to make the compaction code non-determinstic, influenced by past access patterns, or otherwise change it, resulting in L1 overwrites with a different set of delta records than before the overwrite
The items above are a problem for the [split-brain protection RFC](https://github.com/neondatabase/neon/pull/4919) because it assumes that layer files in S3 are only ever deleted, but never replaced (overPUTted).
For example, if an unresponsive node A becomes active again after control plane has relocated the tenant to a new node B, the node A may overwrite some L1s.
But node B based its world view on the version of node A's `index_part.json` from _before_ the overwrite.
That earlier `index_part.json`` contained the file size of the pre-overwrite L1.
If the overwritten L1 has a different file size, node B will refuse to read data from the overwritten L1.
Effectively, the data in the L1 has become inaccessible to node B.
If node B already uploaded an index part itself, all subsequent attachments will use node B's index part, and run into the same probem.
If we ever introduce checksums instead of checking just the file size, then a mismatching bit pattern (2) will cause similar problems.
In case of (1) and (2), where we know that the logical content of the layers is still the same, we can recover by manually patching the `index_part.json` of the new node to the overwritten L1's file size / checksum.
But if (3) ever happens, the logical content may be different, and, we could have truly lost data.
Given the above considerations, we should avoid making correctness of split-brain protection dependent on overwrites preserving _logical_ layer file contents.
**It is a much cleaner separation of concerns to require that layer files are truly immutable in S3, i.e., PUT once and then only DELETEd, never overwritten (overPUTted).**
## Design
Instead of reconciling a layer map from local timeline directory contents and remote index part, this RFC proposes to view the remote index part as authoritative during timeline load.
Local layer files will be recognized if they match what's listed in remote index part, and removed otherwise.
During **timeline load**, the only thing that matters is the remote index part content.
Essentially, timeline load becomes much like attach, except we don't need to prefix-list the remote timelines.
The local timeline dir's `metadata` file does not matter.
The layer files in the local timeline dir are seen as a nice-to-have cache of layer files that are in the remote index part.
Any layer files in the local timeline dir that aren't in the remote index part are removed during startup.
The `Timeline::load_layer_map()` no longer "merges" local timeline dir contents with the remote index part.
Instead, it treats the remote index part as the authoritative layer map.
If the local timeline dir contains a layer that is in the remote index part, that's nice, and we'll re-use it if file size (and in the future, check sum) match what's stated in the index part.
If it doesn't match, we remove the file from the local timeline dir.
After load, **at runtime**, nothing changes compared to what we did before this RFC.
The procedure for single- and multi-object changes is reproduced here for reference:
* For any new layers that the change adds:
* Write them to a temporary location.
* While holding layer map lock:
* Move them to the final location.
* Insert into layer map.
* Make the S3 changes.
We won't reproduce the remote timeline client method calls here because these are subject to change.
Instead we reproduce the sequence of s3 changes that must result for a given single-/multi-object change:
* PUT layer files inserted by the change.
* PUT an index part that has insertions and deletions of the change.
* DELETE the layer files that are deleted by the change.
Note that it is safe for the DELETE to be deferred arbitrarily.
* If it never happens, we leak the object, but, that's not a correctness concern.
* As of #4938, we don't schedule the remote timeline client operation for deletion immediately, but, only when we drop the `LayerInner`.
* With the [split-brain protection RFC](https://github.com/neondatabase/neon/pull/4919), the deletions will be written to deletion queue for processing when it's safe to do so (see the RFC for details).
## How This Solves The Problem
If we crash before we've finished the S3 changes, then timeline load will reset layer map to the state that's in the S3 index part.
The S3 change sequence above is obviously crash-consistent.
If we crash before the index part PUT, then we leak the inserted layer files to S3.
If we crash after the index part PUT, we leak the to-be-DELETEd layer files to S3.
Leaking is fine, it's a pre-existing condition and not addressed in this RFC.
Multi-object changes that previously created and removed files in timeline dir are now atomic because the layer map updates are atomic and crash consistent:
* atomic layer map update at runtime, currently by using an RwLock in write mode
* atomic `index_part.json` update in S3, as per guarantee that S3 PUT is atomic
* local timeline dir state:
* irrelevant for layer map content => irrelevant for atomic updates / crash consistency
* if we crash after index part PUT, local layer files will be used, so, no on-demand downloads neede for them
* if we crash before index part PUT, local layer files will be deleted
## Trade-Offs
### Fundamental
If we crash before finishing the index part PUT, we lose all the work that hasn't reached the S3 `index_part.json`:
* wal ingest: we lose not-yet-uploaded L0s; load on the **safekeepers** + work for pageserver
* compaction: we lose the entire compaction iteration work; need to re-do it again
* gc: no change to what we have today
If the work is still deemed necessary after restart, the restarted restarted pageserver will re-do this work.
The amount of work to be re-do is capped to the lag of S3 changes to the local changes.
Assuming upload queue allows for unlimited queue depth (that's what it does today), this means:
* on-demand downloads that were needed to do the work: are likely still present, not lost
* wal ingest: currently unbounded
* L0 => L1 compaction: CPU time proportional to `O(sum(L0 size))` and upload work proportional to `O()`
* Compaction threshold is 10 L0s and each L0 can be up to 256M in size. Target size for L1 is 128M.
* In practive, most L0s are tiny due to 10minute `DEFAULT_CHECKPOINT_TIMEOUT`.
* image layer generation: CPU time `O(sum(input data))` + upload work `O(sum(new image layer size))`
* I have no intuition how expensive / long-running it is in reality.
* gc: `update_gc_info`` work (not substantial, AFAIK)
To limit the amount of lost upload work, and ingest work, we can limit the upload queue depth (see suggestions in the next sub-section).
However, to limit the amount of lost CPU work, we would need a way to make make the compaction/image-layer-generation algorithms interruptible & resumable.
We aren't there yet, the need for it is tracked by ([#4580](https://github.com/neondatabase/neon/issues/4580)).
However, this RFC is not constraining the design space either.
### Practical
#### Pageserver Restarts
Pageserver crashes are very rare ; it would likely be acceptable to re-do the lost work in that case.
However, regular pageserver restart happen frequently, e.g., during weekly deploys.
In general, pageserver restart faces the problem of tenants that "take too long" to shut down.
They are a problem because other tenants that shut down quickly are unavailble while we wait for the slow tenants to shut down.
We currently allot 10 seconds for graceful shutdown until we SIGKILL the pageserver process (as per `pageserver.service` unit file).
A longer budget would expose tenants that are done early to a longer downtime.
A short budget would risk throwing away more work that'd have to be re-done after restart.
In the context of this RFC, killing the process would mean losing the work that hasn't made it to S3.
We can mitigate this problem as follows:
0. initially, by accepting that we need to do the work again
1. short-term, introducing measures to cap the amount of in-flight work:
- cap upload queue length, use backpressure to slow down compaction
- disabling compaction/image-layer-generation X minutes before `systemctl restart pageserver`
- introducing a read-only shutdown state for tenants that are fast to shut down;
that state would be equivalent to the state of a tenant in hot standby / readonly mode.
2. mid term, by not restarting pageserver in place, but using [*seamless tenant migration*](https://github.com/neondatabase/neon/pull/5029) to drain a pageserver's tenants before we restart it.
#### `disk_consistent_lsn` can go backwards
`disk_consistent_lsn` can go backwards across restarts if we crash before we've finished the index part PUT.
Nobody should care about it, because the only thing that matters is `remote_consistent_lsn`.
Compute certainly doesn't care about `disk_consistent_lsn`.
## Side-Effects Of This Design
* local `metadata` is basically reduced to a cache of which timelines exist for this tenant; i.e., we can avoid a `ListObjects` requests for a tenant's timelines during tenant load.
## Limitations
Multi-object changes that span multiple timelines aren't covered by this RFC.
That's fine because we currently don't need them, as evidenced by the absence
of a Pageserver operation that holds multiple timelines' layer map lock at a time.
## Impacted components
Primarily pageservers.
Safekeepers will experience more load when we need to re-ingest WAL because we've thrown away work.
No changes to safekeepers are needed.
## Alternatives considered
### Alternative 1: WAL
We could have a local WAL for timeline dir changes, as proposed here https://github.com/neondatabase/neon/issues/4418 and partially implemented here https://github.com/neondatabase/neon/pull/4422 .
The WAL would be used to
1. make multi-object changes atomic
2. replace `reconcile_with_remote()` reconciliation: scheduling of layer upload would be part of WAL replay.
The WAL is appealing in a local-first world, but, it's much more complex than the design described above:
* New on-disk state to get right.
* Forward- and backward-compatibility development costs in the future.
### Alternative 2: Flow Everything Through `index_part.json`
We could have gone to the other extreme and **only** update the layer map whenever we've PUT `index_part.json`.
I.e., layer map would always be the last-persisted S3 state.
That's axiomatically beautiful, not least because it fully separates the layer file production and consumption path (=> [layer file spreading proposal](https://www.notion.so/neondatabase/One-Pager-Layer-File-Spreading-Christian-eb6b64182a214e11b3fceceee688d843?pvs=4)).
And it might make hot standbys / read-only pageservers less of a special case in the future.
But, I have some uncertainties with regard to WAL ingestion, because it needs to be able to do some reads for the logical size feedback to safekeepers.
And it's silly that we wouldn't be able to use the results of compaction or image layer generation before we're done with the upload.
Lastly, a temporarily clogged-up upload queue (e.g. S3 is down) shouldn't immediately render ingestion unavailable.
### Alternative 3: Sequence Numbers For Layers
Instead of what's proposed in this RFC, we could use unique numbers to identify layer files:
To guarantee uniqueness, the unqiue number is a sequence number, stored in `index_part.json`.
This alternative does not solve atomic layer map updates.
In our crash-during-compaction scenario above, the compaction run after the crash will not overwrite the L1s, but write/PUT new files with new sequence numbers.
In fact, this alternative makes it worse because the data is now duplicated in the not-overwritten and overwritten L1 layer files.
We'd need to write a deduplication pass that checks if perfectly overlapping layers have identical contents.
However, this alternative is appealing because it systematically prevents overwrites at a lower level than this RFC.
So, this alternative is sufficient for the needs of the split-brain safety RFC (immutable layer files locally and in S3).
But it doesn't solve the problems with crash-during-compaction outlined earlier in this RFC, and in fact, makes it much more accute.
The proposed design in this RFC addresses both.
So, if this alternative sounds appealing, we should implement the proposal in this RFC first, then implement this alternative on top.
That way, we avoid a phase where the crash-during-compaction problem is accute.
Note that the test case introduced in https://github.com/neondatabase/neon/pull/4696/files#diff-13114949d1deb49ae394405d4c49558adad91150ba8a34004133653a8a5aeb76 will produce L1s with the same logical content, but, as outlined in the last paragraph of the _Problem Statement_ section above, we don't want to make that assumption in order to fix the problem.
## Implementation Plan
1. Remove support for `remote_storage=None`, because we now rely on the existence of an index part.
- The nasty part here is to fix all the tests that fiddle with the local timeline directory.
Possibly they are just irrelevant with this change, but, each case will require inspection.
2. Implement the design above.
- Initially, ship without the mitigations for restart and accept we will do some work twice.
- Measure the impact and implement one of the mitigations.
The preceding [generation numbers RFC](025-generation-numbers.md) may be thought of as "making tenant
migration safe". Following that,
this RFC is about how those migrations are to be done:
1. Seamlessly (without interruption to client availability)
2. Quickly (enabling faster operations)
3. Efficiently (minimizing I/O and $ cost)
These points are in priority order: if we have to sacrifice
efficiency to make a migration seamless for clients, we will
do so, etc.
This is accomplished by introducing two high level changes:
- A dual-attached state for tenants, used in a control-plane-orchestrated
migration procedure that preserves availability during a migration.
- Warm secondary locations for tenants, where on-disk content is primed
for a fast migration of the tenant from its current attachment to this
secondary location.
## Motivation
Migrating tenants between pageservers is essential to operating a service
at scale, in several contexts:
1. Responding to a pageserver node failure by migrating tenants to other pageservers
2. Balancing load and capacity across pageservers, for example when a user expands their
database and they need to migrate to a pageserver with more capacity.
3. Restarting pageservers for upgrades and maintenance
The current situation steps for migration are:
- detach from old node; skip if old node is dead; (the [skip part is still WIP](https://github.com/neondatabase/cloud/issues/5426)).
- attach to new node
- re-configure endpoints to use the new node
Once [generation numbers](025-generation-numbers.md) are implemented,
the detach step is no longer critical for correctness. So, we can
- attach to a new node,
- re-configure endpoints to use the new node, and then
- detach from the old node.
However, this still does not meet our seamless/fast/efficient goals:
- Not fast: The new node will have to download potentially large amounts
of data from S3, which may take many minutes.
- Not seamless: If we attach to a new pageserver before detaching an old one,
the new one might delete some objects that interrupt availability of reads on the old one.
- Not efficient: the old pageserver will continue uploading
S3 content during the migration that will never be read.
The user expectations for availability are:
- For planned maintenance, there should be zero availability
gap. This expectation is fulfilled by this RFC.
- For unplanned changes (e.g. node failures), there should be
minimal availability gap. This RFC provides the _mechanism_
to fail over quickly, but does not provide the failure _detection_
nor failover _policy_.
## Non Goals
- Defining service tiers with different storage strategies: the same
level of HA & overhead will apply to all tenants. This doesn't rule out
adding such tiers in future.
- Enabling pageserver failover in the absence of a control plane: the control
plane will remain the source of truth for what should be attached where.
- Totally avoiding availability gaps on unplanned migrations during
a failure (we expect a small, bounded window of
read unavailability of very recent LSNs)
- Workload balancing: this RFC defines the mechanism for moving tenants
around, not the higher level logic for deciding who goes where.
- Defining all possible configuration flows for tenants: the migration process
defined in this RFC demonstrates the sufficiency of the pageserver API, but
is not the only kind of configuration change the control plane will ever do.
The APIs defined here should let the control plane move tenants around in
whatever way is needed while preserving data safety and read availability.
## Impacted components
Pageserver, control plane
## Terminology
- **Attachment**: a tenant is _attached_ to a pageserver if it has
been issued a generation number, and is running an instance of
the `Tenant` type, ingesting the WAL, and available to serve
page reads.
- **Location**: locations are a superset of attachments. A location
is a combination of a tenant and a pageserver. We may _attach_ at a _location_.
- **Secondary location**: a location which is not currently attached.
- **Warm secondary location**: a location which is not currently attached, but is endeavoring to maintain a warm local cache of layers. We avoid calling this a _warm standby_ to avoid confusion with similar postgres features.
## Implementation (high level)
### Warm secondary locations
To enable faster migrations, we will identify at least one _secondary location_
for each tenant. This secondary location will keep a warm cache of layers
for the tenant, so that if it is later attached, it can catch up with the
latest LSN quickly: rather than downloading everything, it only has to replay
the recent part of the WAL to advance from the remote_consistent_offset to the
most recent LSN in the WAL.
The control plane is responsible for selecting secondary locations, and
calling into pageservers to configure tenants into a secondary mode at this
new location, as well as attaching the tenant in its existing primary location.
The attached pageserver for a tenant will publish a [layer heatmap](#layer-heatmap)
to advise secondaries of which layers should be downloaded.
### Location modes
Currently, we consider a tenant to be in one of two states on a pageserver:
- Attached: active `Tenant` object, and layers on local disk
- Detached: no layers on local disk, no runtime state.
We will extend this with finer-grained modes, whose purpose will become
clear in later sections:
- **AttachedSingle**: equivalent the existing attached state.
- **AttachedMulti**: like AttachedSingle, holds an up to date generation, but
does not do deletions.
- **AttachedStale**: like AttachedSingle, holds a stale generation,
do not do any remote storage operations.
- **Secondary**: keep local state on disk, periodically update from S3.
- **Detached**: equivalent to existing detached state.
To control these finer grained states, a new pageserver API endpoint will be added.
### Cutover procedure
Define old location and new location as "Node A" and "Node B". Consider
the case where both nodes are available, and Node B was previously configured
as a secondary location for the tenant we are migrating.
The cutover procedure is orchestrated by the control plane, calling into
the pageservers' APIs:
1. Call to Node A requesting it to flush to S3 and enter AttachedStale state
2. Increment generation, and call to Node B requesting it to enter AttachedMulti
state with the new generation.
3. Call to Node B, requesting it to download the latest hot layers from remote storage,
according to the latest heatmap flushed by Node A.
4. Wait for Node B's WAL ingestion to catch up with node A's
5. Update endpoints to use node B instead of node A
6. Call to node B requesting it to enter state AttachedSingle.
7. Call to node A requesting it to enter state Secondary
The following table summarizes how the state of the system advances:
| Step | Node A | Node B | Node used by endpoints |
- It is legacy for a Project to have zero `ProjectLocation`s
- The `pageserver` column in `Project` now means "to which pageserver should
endpoints connect", rather than simply which pageserver is attached.
- The `generation` column in `Project` remains, and is incremented and used
to set the generation of `ProjectLocation` rows when they are set into
an attached state.
- The `Detached` state is implicitly represented as the absence of
a `ProjectLocation`.
### Executing migrations
Migrations will be implemented as Go functions, within the
existing `Operation` framework in the control plane. These
operations are persistent, such that they will always keep
trying until completion: this property is important to avoid
leaving garbage behind on pageservers, such as AttachedStale
locations.
### Recovery from failures during migration
During migration, the control plane may encounter failures of either
the original or new pageserver, or both:
- If the original fails, skip past waiting for the new pageserver
to catch up, and put it into AttachedSingle immediately.
- If the new node fails, put the old pageserver into Secondary
and then back into AttachedSingle (this has the effect of
retaining on-disk state and granting it a fresh generation number).
- If both nodes fail, keep trying until one of them is available
again.
### Control plane -> Pageserver reconciliation
A migration may be done while the old node is unavailable,
in which case the old node may still be running in an AttachedStale
state.
In this case, it is undesirable to have the migration `Operation`
stay alive until the old node eventually comes back online
and can be cleaned up. To handle this, the control plane
should run a background reconciliation process to compare
a pageserver's attachments with the database, and clean up
any that shouldn't be there any more.
Note that there will be no work to do if the old node was really
offline, as during startup it will call into `/re-attach` and
be updated that way. The reconciliation will only be needed
if the node was unavailable but still running.
## Alternatives considered
### Only enabling secondary locations for tenants on a higher service tier
This will make sense in future, especially for tiny databases that may be
downloaded from S3 in milliseconds when needed.
However, it is not wise to do it immediately, because pageservers contain
a mixture of higher and lower tier workloads. If we had 1 tenant with
a secondary location and 9 without, then those other 9 tenants will do
a lot of I/O as they try to recover from S3, which may degrade the
service of the tenant which had a secondary location.
Until we segregate tenant on different service tiers on different pageserver
nodes, or implement & test QoS to ensure that tenants with secondaries are
not harmed by tenants without, we should use the same failover approach
for all the tenants.
### Hot secondary locations (continuous WAL replay)
Instead of secondary locations populating their caches from S3, we could
have them consume the WAL from safekeepers. The downsides of this would be:
- Double load on safekeepers, which are a less scalable service than S3
- Secondary locations' on-disk state would end up subtly different to
the remote state, which would make synchronizing with S3 more complex/expensive
when going into attached state.
The downside of only updating secondary locations from S3 is that we will
have a delay during migration from replaying the LSN range between what's
in S3 and what's in the pageserver. This range will be very small on
planned migrations, as we have the old pageserver flush to S3 immediately
before attaching the new pageserver. On unplanned migrations (old pageserver
is unavailable), the range of LSNs to replay is bounded by the flush frequency
on the old pageserver. However, the migration doesn't have to wait for the
replay: it's just that not-yet-replayed LSNs will be unavailable for read
until the new pageserver catches up.
We expect that pageserver reads of the most recent LSNs will be relatively
rare, as for an active endpoint those pages will usually still be in the postgres
page cache: this leads us to prefer synchronizing from S3 on secondary
locations, rather than consuming the WAL from safekeepers.
### Cold secondary locations
It is not functionally necessary to keep warm caches on secondary locations at all. However, if we do not, then
we would experience a de-facto availability loss in unplanned migrations, as reads to the new node would take an extremely long time (many seconds, perhaps minutes).
Warm caches on secondary locations are necessary to meet
our availability goals.
### Pageserver-granularity failover
Instead of migrating tenants individually, we could have entire spare nodes,
and on a node death, move all its work to one of these spares.
This approach is avoided for several reasons:
- we would still need fine-grained tenant migration for other
purposes such as balancing load
- by sharing the spare capacity over many peers rather than one spare node,
these peers may use the capacity for other purposes, until it is needed
to handle migrated tenants. e.g. for keeping a deeper cache of their
attached tenants.
### Readonly during migration
We could simplify migrations by making both previous and new nodes go into a
readonly state, then flush remote content from the previous node, then activate
attachment on the secondary node.
The downside to this approach is a potentially large gap in readability of
recent LSNs while loading data onto the new node. To avoid this, it is worthwhile
to incur the extra cost of double-replaying the WAL onto old and new nodes' local
storage during a migration.
### Peer-to-peer pageserver communication
Rather than uploading the heatmap to S3, attached pageservers could make it
available to peers.
Currently, pageservers have no peer to peer communication, so adding this
for heatmaps would incur significant overhead in deployment and configuration
of the service, and ensuring that when a new pageserver is deployed, other
pageservers are updated to be aware of it.
As well as simplifying implementation, putting heatmaps in S3 will be useful
for future analytics purposes -- gathering aggregated statistics on activity
pattersn across many tenants may be done directly from data in S3.
This readme contains some hints on how to set up some optional development tools.
## ccls
[ccls](https://github.com/MaskRay/ccls) is a c/c++ language server. It requires some setup
to work well. There are different ways to do it but here's what works for me:
1. Make a common parent directory for all your common neon projects. (for example, `~/src/neondatabase/`)
2. Go to `vendor/postgres-v15`
3. Run `make clean && ./configure`
4. Install [bear](https://github.com/rizsotto/Bear), and run `bear -- make -j4`
5. Copy the generated `compile_commands.json` to `~/src/neondatabase` (or equivalent)
6. Run `touch ~/src/neondatabase/.ccls-root` this will make the `compile_commands.json` file discoverable in all subdirectories
With this setup you will get decent lsp mileage inside the postgres repo, and also any postgres extensions that you put in `~/src/neondatabase/`, like `pg_embedding`, or inside `~/src/neondatabase/neon/pgxn` as well.
Some additional tips for various IDEs:
### Emacs
To improve performance: `(setq lsp-lens-enable nil)`
"address_standardizer.control":"# address_standardizer extension\ncomment = ''Used to parse an address into constituent elements. Generally used to support geocoding address normalization step.''\ndefault_version = ''3.3.2''\nrelocatable = true\ntrusted = true\n",
# to use tokio channels as streams, this is faster to compile than async_stream
# why is it only here? no other crate should use it, streams are rarely needed.
tokio-stream={version="0.1.14"}
[dev-dependencies]
byteorder.workspace=true
bytes.workspace=true
criterion.workspace=true
hex-literal.workspace=true
tempfile.workspace=true
camino-tempfile.workspace=true
[[bench]]
name="benchmarks"
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