This PR adds a component-level benchmarking utility for pageserver.
Its name is `pagebench`.
The problem solved by `pagebench` is that we want to put Pageserver
under high load.
This isn't easily achieved with `pgbench` because it needs to go through
a compute, which has signficant performance overhead compared to
accessing Pageserver directly.
Further, compute has its own performance optimizations (most
importantly: caches). Instead of designing a compute-facing workload
that defeats those internal optimizations, `pagebench` simply bypasses
them by accessing pageserver directly.
Supported benchmarks:
* getpage@latest_lsn
* basebackup
* triggering logical size calculation
This code has no automated users yet.
A performance regression test for getpage@latest_lsn will be added in a
later PR.
part of https://github.com/neondatabase/neon/issues/5771
Adds a new disk usage based eviction option, EvictionOrder, which
selects whether to use the current `AbsoluteAccessed` or this new
proposed but not yet tested `RelativeAccessed`. Additionally a fudge
factor was noticed while implementing this, which might help sparing
smaller tenants at the expense of targeting larger tenants.
Cc: #5304
Co-authored-by: Arpad Müller <arpad@neon.tech>
This is a precursor to:
- https://github.com/neondatabase/neon/pull/6185
While that PR contains big changes to neon_local and attachment_service,
this PR contains a few unrelated standalone changes generated while
working on that branch:
- Fix restarting a pageserver when it contains multiple shards for the
same tenant
- When using location_config api to attach a tenant, create its
timelines dir
- Update test paths where generations were previously optional to make
them always-on: this avoids tests having to spuriously assert that
attachment_service is not None in order to make the linter happy.
- Add a TenantShardId python implementation for subsequent use in test
helpers that will be made shard-aware
- Teach scrubber to read across shards when checking for layer
existence: this is a refactor to track the list of existent layers at
tenant-level rather than locally to each timeline. This is a precursor
to testing shard splitting.
It wasn't being incremented.
Fixup of
commit 1c88824ed0
Author: Christian Schwarz <christian@neon.tech>
Date: Fri Dec 1 12:52:59 2023 +0100
initial logical size calculation: add a bunch of metrics (#5995)
This squashes a particularly noisy warn-level log that occurs when
safekeepers are restarted.
Unfortunately the error type from `tonic` doesn't provide a neat way of
matching this, so we use a string comparison
Part of getpage@lsn benchmark epic:
https://github.com/neondatabase/neon/issues/5771
This allows getting the list of tenants and timelines without triggering
initial logical size calculation by requesting the timeline details API
response, which would skew our results.
## Problem
#6112 added some logs and metrics: clean these up a bit:
- Avoid counting startup completions for tenants launched after startup
- exclude no-op cases from timing histograms
- remove a rogue log messages
## Problem
During startup, a client request might have to wait a long time while
the system is busy initializing all the attached tenants, even though
most of the attached tenants probably don't have any client requests to
service, and could wait a bit.
## Summary of changes
- Add a semaphore to limit how many Tenant::spawn()s may concurrently do
I/O to attach their tenant (i.e. read indices from remote storage, scan
local layer files, etc).
- Add Tenant::activate_now, a hook for kicking a tenant in its spawn()
method to skip waiting for the warmup semaphore
- For tenants that attached via warmup semaphore units, wait for logical
size calculation to complete before dropping the warmup units
- Set Tenant::activate_now in `get_active_tenant_with_timeout` (the page
service's path for getting a reference to a tenant).
- Wait for tenant activation in HTTP handlers for timeline creation and
deletion: like page service requests, these require an active tenant and
should prioritize activation if called.
## Problem
Various places in remote storage were not subject to a timeout (thereby
stuck TCP connections could hold things up), and did not respect a
cancellation token (so things like timeline deletion or tenant detach
would have to wait arbitrarily long).
## Summary of changes
- Add download_cancellable and upload_cancellable helpers, and use them
in all the places we wait for remote storage operations (with the
exception of initdb downloads, where it would not have been safe).
- Add a cancellation token arg to `download_retry`.
- Use cancellation token args in various places that were missing one
per #5066Closes: #5066
Why is this only "basic" handling?
- Doesn't express difference between shutdown and errors in return
types, to avoid refactoring all the places that use an anyhow::Error
(these should all eventually return a more structured error type)
- Implements timeouts on top of remote storage, rather than within it:
this means that operations hitting their timeout will lose their
semaphore permit and thereby go to the back of the queue for their
retry.
- Doing a nicer job is tracked in
https://github.com/neondatabase/neon/issues/6096
Part of getpage@lsn benchmark epic:
https://github.com/neondatabase/neon/issues/5771
This PR moves the control plane's spread-all-over-the-place client for
the pageserver management API into a separate module within the
pageserver crate.
I need that client to be async in my benchmarking work, so, this PR
switches to the async version of `reqwest`.
That is also the right direction generally IMO.
The switch to async in turn mandated converting most of the
`control_plane/` code to async.
Note that some of the client methods should be taking `TenantShardId`
instead of `TenantId`, but, none of the callers seem to be
sharding-aware.
Leaving that for another time:
https://github.com/neondatabase/neon/issues/6154
* initdb uploads had no cancellation token, which means that when we
were stuck in upload retries, we wouldn't be able to delete the
timeline. in general, the combination of retrying forever and not having
cancellation tokens is quite dangerous.
* initdb uploads wouldn't rewind the file. this wasn't discovered in the
purposefully unreliable test-s3 in pytest because those fail on the
first byte always, not somewhere during the connection. we'd be getting
errors from the AWS sdk that the file was at an unexpected end.
slack thread: https://neondb.slack.com/archives/C033RQ5SPDH/p1702632247784079
Compaction was holding back timeline deletion because the compaction
lock had been acquired, but the semaphore was waited on. Timeline
deletion was waiting on the same lock for 1500s.
This replaces the
`pageserver::tenant::tasks::concurrent_background_tasks_rate_limit`
(which looks correct) with a simpler `..._permit` which is just an
infallible acquire, which is easier to spot "aah this needs to be raced
with cancellation tokens".
Ref: https://neondb.slack.com/archives/C03F5SM1N02/p1702496912904719
Ref: https://neondb.slack.com/archives/C03F5SM1N02/p1702578093497779
Before any json parsing from the http api only returned errors were per
field errors. Now they are done using `serde_path_to_error`, which at
least helped greatly with the `disk_usage_eviction_run` used for
testing. I don't think this can conflict with anything added in #5310.
## Problem
Historically, the pageserver used an "uninit mark" file on disk for two
purposes:
- Track which timeline dirs are incomplete for handling on restart
- Avoid trying to create the same timeline twice at the same time.
The original purpose of handling restarts is now defunct, as we use
remote storage as the source of truth and clean up any trash timeline
dirs on startup. Using the file to mutually exclude creation operations
is error prone compared with just doing it in memory, and the existing
checks happened some way into the creation operation, and could expose
errors as 500s (anyhow::Errors) rather than something clean.
## Summary of changes
- Creations are now mutually excluded in memory (using
`Tenant::timelines_creating`), rather than relying on a file on disk for
coordination.
- Acquiring unique access to the timeline ID now happens earlier in the
request.
- Creating the same timeline which already exists is now a 201: this
simplifies retry handling for clients.
- 409 is still returned if a timeline with the same ID is still being
created: if this happens it is probably because the client timed out an
earlier request and has retried.
- Colliding timeline creation requests should no longer return 500
errors
This paves the way to entirely removing uninit markers in a subsequent
change.
---------
Co-authored-by: Joonas Koivunen <joonas@neon.tech>
## Problem
The websockets gauge for active db connections seems to be growing more
than the gauge for client connections over websockets, which does not
make sense.
## Summary of changes
refactor how our counter-pair gauges are represented. not sure if this
will improve the problem, but it should be harder to mess-up the
counters. The API is much nicer though now and doesn't require
scopeguard::defer hacks
Dependency (commits inline):
https://github.com/neondatabase/neon/pull/5842
## Problem
Secondary mode tenants need a manifest of what to download. Ultimately
this will be some kind of heat-scored set of layers, but as a robust
first step we will simply use the set of resident layers: secondary
tenant locations will aim to match the on-disk content of the attached
location.
## Summary of changes
- Add heatmap types representing the remote structure
- Add hooks to Tenant/Timeline for generating these heatmaps
- Create a new `HeatmapUploader` type that is external to `Tenant`, and
responsible for walking the list of attached tenants and scheduling
heatmap uploads.
Notes to reviewers:
- Putting the logic for uploads (and later, secondary mode downloads)
outside of `Tenant` is an opinionated choice, motivated by:
- Enable future smarter scheduling of operations, e.g. uploading the
stalest tenant first, rather than having all tenants compete for a fair
semaphore on a first-come-first-served basis. Similarly for downloads,
we may wish to schedule the tenants with the hottest un-downloaded
layers first.
- Enable accessing upload-related state without synchronization (it
belongs to HeatmapUploader, rather than being some Mutex<>'d part of
Tenant)
- Avoid further expanding the scope of Tenant/Timeline types, which are
already among the largest in the codebase
- You might reasonably wonder how much of the uploader code could be a
generic job manager thing. Probably some of it: but let's defer pulling
that out until we have at least two users (perhaps secondary downloads
will be the second one) to highlight which bits are really generic.
Compromises:
- Later, instead of using digests of heatmaps to decide whether anything
changed, I would prefer to avoid walking the layers in tenants that
don't have changes: tracking that will be a bit invasive, as it needs
input from both remote_timeline_client and Layer.
Changes I wanted to make on #6106 but decided to leave out to keep that
commit clean for including in the #6090. Finally remove
`PageReconstructionError::NeedsDownload`.
## Problem
See
https://github.com/neondatabase/company_projects/issues/111https://neondb.slack.com/archives/C03H1K0PGKH/p1700166126954079
## Summary of changes
Do not search for AUX_FILES_KEY in parent timelines
## 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: Arseny Sher <sher-ars@yandex.ru>
## Problem
PG16 is writing null images during relation extension.
And page server implements optimisation which replace WAL record with
FPI with page image.
So instead of WAL record ~30 bytes we store 8kb null page image.
Ans this image is almost useless, because most likely it will be shortly
rewritten with actual page content.
## Summary of changes
Do not materialize wal records with null page FPI.
## 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
TenantId is changing to TenantShardId in many APIs. The swagger had
`format: hex` attributes on some of these IDs. That isn't formally
defined anywhere, but a reasonable person might think it means "hex
digits only", which will no longer be the case once we start using
shard-aware IDs (they're like `<tenant_id>-0001`).
## Summary of changes
- Remove these `format` attributes from all `tenant_id` fields in the
swagger definition
## Problem
- `shutdown_tasks` would log when a particular task was taking a long
time to shut down, but not when it eventually completed. That left one
uncertain as to whether the slow task was the source of a hang, or just
a precursor.
## Summary of changes
- Add a log line after a slow task shutdown
- Add an equivalent in Gate's `warn_if_stuck`, in case we ever need it.
This isn't related to the original issue but was noticed when checking
through these logging paths.
Error indicating request cancellation OR timeline shutdown was deemed as
a reason to exit the background worker that calculated synthetic size.
Fix it to only be considered for avoiding logging such of such errors.
## Problem
In https://github.com/neondatabase/neon/pull/5957, the most essential
types were updated to use TenantShardId rather than TenantId. That
unblocked other work, but didn't fully enable running multiple shards
from the same tenant on the same pageserver.
## Summary of changes
- Use TenantShardId in page cache key for materialized pages
- Update mgr.rs get_tenant() and list_tenants() functions to use a shard
id, and update all callers.
- Eliminate the exactly_one_or_none helper in mgr.rs and all code that
used it
- Convert timeline HTTP routes to use tenant_shard_id
Note on page cache:
```
struct MaterializedPageHashKey {
/// Why is this TenantShardId rather than TenantId?
///
/// Usually, the materialized value of a page@lsn is identical on any shard in the same tenant. However, this
/// this not the case for certain internally-generated pages (e.g. relation sizes). In future, we may make this
/// key smaller by omitting the shard, if we ensure that reads to such pages always skip the cache, or are
/// special-cased in some other way.
tenant_shard_id: TenantShardId,
timeline_id: TimelineId,
key: Key,
}
```
## Problem
The cancellation code was confusing and error prone (as seen before in
our memory leaks).
## Summary of changes
* Use the new `TaskTracker` primitve instead of JoinSet to gracefully
wait for tasks to shutdown.
* Updated libs/utils/completion to use `TaskTracker`
* Remove `tokio::select` in favour of `futures::future::select` in a
specialised `run_until_cancelled()` helper function
These changes help with identifying thrashing.
The existing `pageserver_page_cache_find_victim_iters_total` is already
useful, but, it doesn't tell us how many individual find_victim() calls
are happening, only how many clock-LRU steps happened in the entire
system,
without info about whether we needed to actually evict other data vs
just scan for a long time, e.g., because the cache is large.
The changes in this PR allows us to
1. count each possible outcome separately, esp evictions
2. compute mean iterations/outcome
I don't think anyone except me was paying close attention to
`pageserver_page_cache_find_victim_iters_total` before, so,
I think the slight behavior change of also counting iterations
for the 'iters exceeded' case is fine.
refs https://github.com/neondatabase/cloud/issues/8351
refs https://github.com/neondatabase/neon/issues/5479
## Problem
Currently, if one creates many shards they will all ingest all the data:
not much use! We want them to ingest a proportional share of the data
each.
Closes: #6025
## Summary of changes
- WalIngest object gets a copy of the ShardIdentity for the Tenant it
was created by.
- While iterating the `blocks` part of a decoded record, blocks that do
not match the current shard are ignored, apart from on shard zero where
they are used to update relation sizes in `observe_decoded_block` (but
not stored).
- Before committing a `DataDirModificiation` from a WAL record, we check
if it's empty, and drop the record if so. This check is necessary
(rather than just looking at the `blocks` part) because certain record
types may modify blocks in non-obvious ways (e.g.
`ingest_heapam_record`).
- Add WAL ingest metrics to record the total received, total committed,
and total filtered out
- Behaviour for unsharded tenants is unchanged: they will continue to
ingest all blocks, and will take the fast path through `is_key_local`
that doesn't bother calculating any hashes.
After this change, shards store a subset of the tenant's total data, and
accurate relation sizes are only maintained on shard zero.
---------
Co-authored-by: Arpad Müller <arpad-m@users.noreply.github.com>
Currently using 8kB buffers, raise that to 32kB to hopefully 1/4 of
`spawn_blocking` usage. Also a drive-by fixing of last `tokio::io::copy`
to `tokio::io::copy_buf`.
There is double buffering in remote_storage and in pageserver for 8KiB
in using `tokio::io::copy` to read `BufReader<ReaderStream<_>>`.
Switches downloads and uploads to use `Stream<Item =
std::io::Result<Bytes>>`. Caller and only caller now handles setting up
buffering. For reading, `Stream<Item = ...>` is also a `AsyncBufRead`,
so when writing to a file, we now have `tokio::io::copy_buf` reading
full buffers and writing them to `tokio::io::BufWriter` which handles
the buffering before dispatching over to `tokio::fs::File`.
Additionally implements streaming uploads for azure. With azure
downloads are a bit nicer than before, but not much; instead of one huge
vec they just hold on to N allocations we got over the wire.
This PR will also make it trivial to switch reading and writing to
io-uring based methods.
Cc: #5563.
## Problem
Some existing tests are written in a way that's incompatible with tenant
generations.
## Summary of changes
Update all the tests that need updating: this is things like calling
through the NeonPageserver.tenant_attach helper to get a generation
number, instead of calling directly into the pageserver API. There are
various more subtle cases.
Per [feedback], split the Layer metrics, also finally account for lost
and [re-submitted feedback] on `layer_gc` by renaming it to
`layer_delete`, `Layer::garbage_collect_on_drop` renamed to
`Layer::delete_on_drop`. References to "gc" dropped from metric names
and elsewhere.
Also fixes how the cancellations were tracked: there was one rare
counter. Now there is a top level metric for cancelled inits, and the
rare "download failed but failed to communicate" counter is kept.
Fixes: #6027
[feedback]: https://github.com/neondatabase/neon/pull/5809#pullrequestreview-1720043251
[re-submitted feedback]: https://github.com/neondatabase/neon/pull/5108#discussion_r1401867311
The gc_timeline() function is async, but it calls the synchronous wait()
function. In the worst case, that could lead to a deadlock by using up
all tokio executor threads.
In the passing, fix a few typos in comments.
Fixes issue #6045.
---------
Co-authored-by: Joonas Koivunen <joonas@neon.tech>
to_string forces allocating a less than pointer sized string (costing on
stack 4 usize), using a Display formattable slug saves that. the
difference seems small, but at the same time, we log these a lot.
- The `Attaching tenant` log message omitted some useful information
like the generation and mode
- info-level messages about writing configuration files were
unnecessarily verbose
- During process shutdown, we don't emit logs about the various phases:
this is very cheap to log since we do it once per process lifetime, and
is helpful when figuring out where something got stuck during a hang.
## Problem
Traditionally we would detach/attach directly with curl if we wanted to
"reboot" a single tenant. That's kind of inconvenient these days,
because one needs to know a generation number to issue an attach
request.
Closes: https://github.com/neondatabase/neon/issues/6011
## Summary of changes
- Introduce a new `/reset` API, which remembers the LocationConf from
the current attachment so that callers do not have to work out the
correct configuration/generation to use.
- As an additional support tool, allow an optional `drop_cache` query
parameter, for situations where we are concerned that some on-disk state
might be bad and want to clear that as well as the in-memory state.
One might wonder why I didn't call this "reattach" -- it's because
there's already a PS->CP API of that name and it could get confusing.
