## Problem
LKB-197, #9516
To make sure the migration path is smooth.
The previous plan is to store new relations in new keyspace and old ones
in old keyspace until it gets dropped. This makes the migration path
hard as we can't validate v2 writes and can't rollback. This patch gives
us a more smooth migration path:
- The first time we enable reldirv2 for a tenant, we copy over
everything in the old keyspace to the new one. This might create a short
spike of latency for the create relation operation, but it's oneoff.
- After that, we have identical v1/v2 keyspace and read/write both of
them. We validate reads every time we list the reldirs.
- If we are in `migrating` mode, use v1 as source of truth and log a
warning for failed v2 operations. If we are in `migrated` mode, use v2
as source of truth and error when writes fail.
- One compatibility test uses dataset from the time where we enabled
reldirv2 (of the original rollout plan), which only has relations
written to the v2 keyspace instead of the v1 keyspace. We had to adjust
it accordingly.
- Add `migrated_at` in index_part to indicate the LSN where we did the
initialize.
TODOs:
- Test if relv1 can be read below the migrated_at LSN.
- Move the initialization process to L0 compaction instead of doing it
on the write path.
- Disable relcache in the relv2 test case so that all code path gets
fully tested.
## Summary of changes
- New behavior of reldirv2 migration flags as described above.
---------
Signed-off-by: Alex Chi Z <chi@neon.tech>
Introduce a separate `postgres_ffi_types` crate which contains a few
types and functions that were used in the API. `postgres_ffi_types` is a
much small crate than `postgres_ffi`, and it doesn't depend on bindgen
or the Postgres C headers.
Move NeonWalRecord and Value types to wal_decoder crate. They are only
used in the pageserver-safekeeper "ingest" API. The rest of the ingest
API types are defined in wal_decoder, so move these there as well.
Introduces a `WalIngestError` struct together with a
`WalIngestErrorKind` enum, to be used for walingest related failures and
errors.
* the enum captures backtraces, so we don't regress in comparison to
`anyhow::Error`s (backtraces might be a bit shorter if we use one of the
`anyhow::Error` wrappers)
* it explicitly lists most/all of the potential cases that can occur.
I've originally been inspired to do this in #11496, but it's a
longer-term TODO.
Updates storage components to edition 2024. We like to stay on the
latest edition if possible. There is no functional changes, however some
code changes had to be done to accommodate the edition's breaking
changes.
The PR has two commits:
* the first commit updates storage crates to edition 2024 and appeases
`cargo clippy` by changing code. i have accidentially ran the formatter
on some files that had other edits.
* the second commit performs a `cargo fmt`
I would recommend a closer review of the first commit and a less close
review of the second one (as it just runs `cargo fmt`).
part of https://github.com/neondatabase/neon/issues/10918
## Problem
Currently, we call `InterpretedWalRecord::from_bytes_filtered`
from each shard. To serve multiple shards at the same time,
the API needs to allow for enquiring about multiple shards.
## Summary of changes
This commit tweaks it a pretty brute force way. Naively, we could
just generate the shard for a key, but pre and post split shards
may be subscribed at the same time, so doing it efficiently is more
complex.
## Problem
Decoding and ingestion are still coupled in `pageserver::WalIngest`.
## Summary of changes
A new type is added to `wal_decoder::models`, InterpretedWalRecord. This
type contains everything that the pageserver requires in order to ingest
a WAL record. The highlights are the `metadata_record` which is an
optional special record type to be handled and `blocks` which stores
key, value pairs to be persisted to storage.
This type is produced by
`wal_decoder::models::InterpretedWalRecord::from_bytes` from a raw PG
wal record.
The rest of this commit separates decoding and interpretation of the PG
WAL record from its application in `WalIngest::ingest_record`.
Related: https://github.com/neondatabase/neon/issues/9335
Epic: https://github.com/neondatabase/neon/issues/9329
## Problem
We wish to have high level WAL decoding logic in `wal_decoder::decoder`
module.
## Summary of Changes
For this we need the `Value` and `NeonWalRecord` types accessible there, so:
1. Move `Value` and `NeonWalRecord` to `pageserver::value` and
`pageserver::record` respectively.
2. Get rid of `pageserver::repository` (follow up from (1))
3. Move PG specific WAL record types to `postgres_ffi::walrecord`. In
theory they could live in `wal_decoder`, but it would create a circular
dependency between `wal_decoder` and `postgres_ffi`. Long term it makes
sense for those types to be PG version specific, so that will work out nicely.
4. Move higher level WAL record types (to be ingested by pageserver)
into `wal_decoder::models`
Related: https://github.com/neondatabase/neon/issues/9335
Epic: https://github.com/neondatabase/neon/issues/9329
This adds preliminary PG17 support to Neon, based on RC1 / 2024-09-04
07b828e9d4
NOTICE: The data produced by the included version of the PostgreSQL fork
may not be compatible with the future full release of PostgreSQL 17 due to
expected or unexpected future changes in magic numbers and internals.
DO NOT EXPECT DATA IN V17-TENANTS TO BE COMPATIBLE WITH THE 17.0
RELEASE!
Co-authored-by: Anastasia Lubennikova <anastasia@neon.tech>
Co-authored-by: Alexander Bayandin <alexander@neon.tech>
Co-authored-by: Konstantin Knizhnik <knizhnik@neon.tech>
Co-authored-by: Heikki Linnakangas <heikki@neon.tech>
## Problem
Currently, DatadirModification keeps a key-indexed map of all pending
writes, even though we (almost) never need to read back dirty pages for
anything other than metadata pages (e.g. relation sizes).
Related: https://github.com/neondatabase/neon/issues/6345
## Summary of changes
- commit() modifications before ingesting database creation wal records,
so that they are guaranteed to be able to get() everything they need
directly from the underlying Timeline.
- Split dirty pages in DatadirModification into pending_metadata_pages
and pending_data_pages. The data ones don't need to be in a
key-addressable format, so they just go in a Vec instead.
- Special case handling of zero-page writes in DatadirModification,
putting them in a map which is flushed on the end of a WAL record. This
handles the case where during ingest, we might first write a zero page,
and then ingest a postgres write to that page. We used to do this via
the key-indexed map of writes, but in this PR we change the data page
write path to not bother indexing these by key.
My least favorite thing about this PR is that I needed to change the
DatadirModification interface to add the on_record_end call. This is not
very invasive because there's really only one place we use it, but it
changes the object's behaviour from being clearly an aggregation of many
records to having some per-record state. I could avoid this by
implicitly doing the work when someone calls set_lsn or commit -- I'm
open to opinions on whether that's cleaner or dirtier.
## Performance
There may be some efficiency improvement here, but the primary
motivation is to enable an earlier stage of ingest to operate without
access to a Timeline. The `pending_data_pages` part is the "fast path"
bulk write data that can in principle be generated without a Timeline,
in parallel with other ingest batches, and ultimately on the safekeeper.
`test_bulk_insert` on AX102 shows approximately the same results as in
the previous PR #8591:
```
------------------------------ Benchmark results -------------------------------
test_bulk_insert[neon-release-pg16].insert: 23.577 s
test_bulk_insert[neon-release-pg16].pageserver_writes: 5,428 MB
test_bulk_insert[neon-release-pg16].peak_mem: 637 MB
test_bulk_insert[neon-release-pg16].size: 0 MB
test_bulk_insert[neon-release-pg16].data_uploaded: 1,922 MB
test_bulk_insert[neon-release-pg16].num_files_uploaded: 8
test_bulk_insert[neon-release-pg16].wal_written: 1,382 MB
test_bulk_insert[neon-release-pg16].wal_recovery: 18.264 s
test_bulk_insert[neon-release-pg16].compaction: 0.052 s
```
## Problem
Ingest filtering wasn't being applied to timeline creations, so a
timeline created on a sharded tenant would use 20MB+ on each shard (each
shard got a full copy). This didn't break anything, but is inefficient
and leaves the system in a harder-to-validate state where shards
initially have some data that they will eventually drop during
compaction.
Closes: https://github.com/neondatabase/neon/issues/6649
## Summary of changes
- in `import_rel`, filter block-by-block with is_key_local
- During test_sharding_smoke, check that per-shard physical sizes are as
expected
- Also extend the test to check deletion works as expected (this was an
outstanding tech debt task)
## Problem
For context, this problem was observed in a research project where we
try to make neon run in multiple regions and I was asked by @hlinnaka to
make this PR.
In our project, we use the pageserver in a non-conventional way such
that we would send a larger number of requests to the pageserver than
normal (imagine postgres without the buffer pool). I measured the time
from the moment a WAL record left the safekeeper to when it reached the
pageserver
([code](e593db1f5a/pageserver/src/tenant/timeline/walreceiver/walreceiver_connection.rs (L282-L287)))
and observed that when the number of get_page_at_lsn requests was high,
the wal receiving time increased significantly (see the left side of the
graphs below).
Upon further investigation, I found that the delay was caused by this
line
d2ca410919/pageserver/src/tenant/timeline.rs (L2348)
The `get_layer_for_write` method is called for every value during WAL
ingestion and it tries to acquire layers write lock every time, thus
this results in high contention when read lock is acquired more
frequently.
## Summary of changes
It is unnecessary to call `get_layer_for_write` repeatedly for all
values in a WAL message since they would end up in the same memory layer
anyway, so I created the batched versions of `InMemoryLayer::put_value`,
`InMemoryLayer ::put_tombstone`, `Timeline::put_value`, and
`Timeline::put_tombstone`, that acquire the locks once for a batch of
values.
Additionally, `DatadirModification` is changed to store multiple
versions of uncommitted values, and `WalIngest::ingest_record()` can now
ingest records without immediately committing them.
With these new APIs, the new ingestion loop can be changed to commit for
every `ingest_batch_size` records. The `ingest_batch_size` variable is
exposed as a config. If it is set to 1 then we get the same behavior
before this change. I found that setting this value to 100 seems to work
the best, and you can see its effect on the right side of the above
graphs.
---------
Co-authored-by: John Spray <john@neon.tech>
This PR adds an `existing_initdb_timeline_id` option to timeline
creation APIs, taking an optional timeline ID.
Follow-up of #5390.
If the `existing_initdb_timeline_id` option is specified via the HTTP
API, the pageserver downloads the existing initdb archive from the given
timeline ID and extracts it, instead of running initdb itself.
---------
Co-authored-by: Christian Schwarz <christian@neon.tech>
## Problem
See #2592
## Summary of changes
Compresses the results of initdb into a .tar.zst file and uploads them
to S3, to enable usage in recovery from lsn.
Generations should not be involved I think because we do this only once
at the very beginning of a timeline.
---------
Co-authored-by: Joonas Koivunen <joonas@neon.tech>
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>
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.
This is preliminary work for/from #4220 (async
`Layer::get_value_reconstruct_data`).
There, we want to switch `Timeline::layers` to be a
`tokio::sync::RwLock`.
That will require the `TimelineWriter` to become async, because at times
its functions need to lock `Timeline::layers` in order to freeze the
open layer.
While doing that, rustc complains that we're now holding
`Timeline::write_lock` across await points (lock order is that
`write_lock` must be acquired before `Timelines::layers`).
So, we need to switch it over to an async primitive.
Refactoring part of #4093.
Numerious `Send + Sync` bounds were a distraction, that were not needed
at all. The proper `Bytes` usage and one `"error_message".to_string()`
are just drive-by fixes.
Not using the `PostgresBackendTCP` allows us to start setting read
timeouts (and more). `PostgresBackendTCP` is still used from proxy, so
it cannot be removed.
Motivation
==========
Layer Eviction Needs Context
----------------------------
Before we start implementing layer eviction, we need to collect some
access statistics per layer file or maybe even page.
Part of these statistics should be the initiator of a page read request
to answer the question of whether it was page_service vs. one of the
background loops, and if the latter, which of them?
Further, it would be nice to learn more about what activity in the pageserver
initiated an on-demand download of a layer file.
We will use this information to test out layer eviction policies.
Read more about the current plan for layer eviction here:
https://github.com/neondatabase/neon/issues/2476#issuecomment-1370822104
task_mgr problems + cancellation + tenant/timeline lifecycle
------------------------------------------------------------
Apart from layer eviction, we have long-standing problems with task_mgr,
task cancellation, and various races around tenant / timeline lifecycle
transitions.
One approach to solve these is to abandon task_mgr in favor of a
mechanism similar to Golang's context.Context, albeit extended to
support waiting for completion, and specialized to the needs in the
pageserver.
Heikki solves all of the above at once in PR
https://github.com/neondatabase/neon/pull/3228 , which is not yet
merged at the time of writing.
What Is This Patch About
========================
This patch addresses the immediate needs of layer eviction by
introducing a `RequestContext` structure that is plumbed through the
pageserver - all the way from the various entrypoints (page_service,
management API, tenant background loops) down to
Timeline::{get,get_reconstruct_data}.
The struct carries a description of the kind of activity that initiated
the call. We re-use task_mgr::TaskKind for this.
Also, it carries the desired on-demand download behavior of the entrypoint.
Timeline::get_reconstruct_data can then log the TaskKind that initiated
the on-demand download.
I developed this patch by git-checking-out Heikki's big RequestContext
PR https://github.com/neondatabase/neon/pull/3228 , then deleting all
the functionality that we do not need to address the needs for layer
eviction.
After that, I added a few things on top:
1. The concept of attached_child and detached_child in preparation for
cancellation signalling through RequestContext, which will be added in
a future patch.
2. A kill switch to turn DownloadBehavior::Error into a warning.
3. Renamed WalReceiverConnection to WalReceiverConnectionPoller and
added an additional TaskKind WalReceiverConnectionHandler.These were
necessary to create proper detached_child-type RequestContexts for the
various tasks that walreceiver starts.
How To Review This Patch
========================
Start your review with the module-level comment in context.rs.
It explains the idea of RequestContext, what parts of it are implemented
in this patch, and the future plans for RequestContext.
Then review the various `task_mgr::spawn` call sites. At each of them,
we should be creating a new detached_child RequestContext.
Then review the (few) RequestContext::attached_child call sites and
ensure that the spawned tasks do not outlive the task that spawns them.
If they do, these call sites should use detached_child() instead.
Then review the todo_child() call sites and judge whether it's worth the
trouble of plumbing through a parent context from the caller(s).
Lastly, go through the bulk of mechanical changes that simply forwards
the &ctx.
This makes Timeline::get() async, and all functions that call it
directly or indirectly with it. The with_ondemand_download() mechanism
is gone, Timeline::get() now always downloads files, whether you want
it or not. That is what all the current callers want, so even though
this loses the capability to get a page only if it's already in the
pageserver, without downloading, we were not using that capability.
There were some places that used 'no_ondemand_download' in the WAL
ingestion code that would error out if a layer file was not found
locally, but those were dubious. We do actually want to on-demand
download in all of those places.
Per discussion at
https://github.com/neondatabase/neon/pull/3233#issuecomment-1368032358
Makes the top-level functions in WalIngest async, and replaces
no_ondemand_download calls with with_ondemand_download.
This hopefully fixes the problem reported in issue #3230, although I
don't have a self-contained test case for it.
The synchronous 'tar' crate has required us to use block_in_place and
SyncIoBridge to work together with the async I/O in the client
connection. Switch to 'tokio-tar' crate that uses async I/O natively.
As part of this, move the CopyDataWriter implementation to
postgres_backend_async.rs. Even though it's only used in one place
currently, it's in principle generally applicable whenever you want to
use COPY out.
Unfortunately we cannot use the 'tokio-tar' as it is: the Builder
implementation requires the writer to have 'static lifetime. So we
have to use a modified version without that requirement. The 'static
lifetime was required just for the Drop implementation that writes
the end-of-archive sections if the Builder is dropped without calling
`finish`. But we don't actually want that behavior anyway; in fact
we had to jump through some hoops with the AbortableWrite hack to skip
those. With the modified version of 'tokio-tar' without that Drop
implementation, we don't need AbortableWrite either.
Co-authored-by: Kirill Bulatov <kirill@neon.tech>
The PR aims to fix two missing redownloads in a flacky
test_remote_storage_upload_queue_retries[local_fs]
([example](https://neon-github-public-dev.s3.amazonaws.com/reports/pr-3190/release/3759194738/index.html#categories/80f1dcdd7c08252126be7e9f44fe84e6/8a70800f7ab13620/))
1. missing redownload during walreceiver work
```
2022-12-22T16:09:51.509891Z ERROR wal_connection_manager{tenant=fb62b97553e40f949de8bdeab7f93563 timeline=4f153bf6a58fd63832f6ee175638d049}: wal receiver task finished with an error: walreceiver connection handling failure
Caused by:
Layer needs downloading
Stack backtrace:
0: pageserver::tenant::timeline::PageReconstructResult<T>::no_ondemand_download
at /__w/neon/neon/pageserver/src/tenant/timeline.rs:467:59
1: pageserver::walingest::WalIngest::new
at /__w/neon/neon/pageserver/src/walingest.rs:61:32
2: pageserver::walreceiver::walreceiver_connection::handle_walreceiver_connection::{{closure}}
at /__w/neon/neon/pageserver/src/walreceiver/walreceiver_connection.rs:178:25
....
```
That looks sad, but inevitable during the current approach: seems that
we need to wait for old layers to arrive in order to accept new data.
For that, `WalIngest::new` now started to return the
`PageReconstructResult`.
Sync methods from `import_datadir.rs` use `WalIngest::new` too, but both
of them import WAL during timeline creation, so no layers to download
are needed there, ergo the `PageReconstructResult` is converted to
`anyhow::Result` with `no_ondemand_download`.
2. missing redownload during compaction work
```
2022-12-22T16:09:51.090296Z ERROR compaction_loop{tenant_id=fb62b97553e40f949de8bdeab7f93563}:compact_timeline{timeline=4f153bf6a58fd63832f6ee175638d049}: could not compact, repartitioning keyspace failed: Layer needs downloading
Stack backtrace:
0: pageserver::tenant::timeline::PageReconstructResult<T>::no_ondemand_download
at /__w/neon/neon/pageserver/src/tenant/timeline.rs:467:59
1: pageserver::pgdatadir_mapping::<impl pageserver::tenant::timeline::Timeline>::collect_keyspace::{{closure}}
at /__w/neon/neon/pageserver/src/pgdatadir_mapping.rs:506:41
<core::future::from_generator::GenFuture<T> as core::future::future::Future>::poll
at /rustc/e092d0b6b43f2de967af0887873151bb1c0b18d3/library/core/src/future/mod.rs:91:19
pageserver::tenant::timeline::Timeline::repartition::{{closure}}
at /__w/neon/neon/pageserver/src/tenant/timeline.rs:2161:50
<core::future::from_generator::GenFuture<T> as core::future::future::Future>::poll
at /rustc/e092d0b6b43f2de967af0887873151bb1c0b18d3/library/core/src/future/mod.rs:91:19
2: pageserver::tenant::timeline::Timeline::compact::{{closure}}
at /__w/neon/neon/pageserver/src/tenant/timeline.rs:700:14
<core::future::from_generator::GenFuture<T> as core::future::future::Future>::poll
at /rustc/e092d0b6b43f2de967af0887873151bb1c0b18d3/library/core/src/future/mod.rs:91:19
3: <tracing::instrument::Instrumented<T> as core::future::future::Future>::poll
at /github/home/.cargo/registry/src/github.com-1ecc6299db9ec823/tracing-0.1.37/src/instrument.rs:272:9
4: pageserver::tenant::Tenant::compaction_iteration::{{closure}}
at /__w/neon/neon/pageserver/src/tenant.rs:1232:85
<core::future::from_generator::GenFuture<T> as core::future::future::Future>::poll
at /rustc/e092d0b6b43f2de967af0887873151bb1c0b18d3/library/core/src/future/mod.rs:91:19
pageserver::tenant_tasks::compaction_loop::{{closure}}::{{closure}}
at /__w/neon/neon/pageserver/src/tenant_tasks.rs:76:62
<core::future::from_generator::GenFuture<T> as core::future::future::Future>::poll
at /rustc/e092d0b6b43f2de967af0887873151bb1c0b18d3/library/core/src/future/mod.rs:91:19
pageserver::tenant_tasks::compaction_loop::{{closure}}
at /__w/neon/neon/pageserver/src/tenant_tasks.rs:91:6
```
1.66 release speeds up compile times for over 10% according to tests.
Also its Clippy finds plenty of old nits in our code:
* useless conversion, `foo as u8` where `foo: u8` and similar, removed
`as u8` and similar
* useless references and dereferenced (that were automatically adjusted
by the compiler), removed various `&` and `*`
* bool -> u8 conversion via `if/else`, changed to `u8::from`
* Map `.iter()` calls where only values were used, changed to
`.values()` instead
Standing out lints:
* `Eq` is missing in our protoc generated structs. Silenced, does not
seem crucial for us.
* `fn default` looks like the one from `Default` trait, so I've
implemented that instead and replaced the `dummy_*` method in tests with
`::default()` invocation
* Clippy detected that
```
if retry_attempt < u32::MAX {
retry_attempt += 1;
}
```
is a saturating add and proposed to replace it.
The code in this change was extracted from #2595 (Heikki’s on-demand
download draft PR).
High-Level Changes
- New RemoteLayer Type
- On-Demand Download As An Effect Of Page Reconstruction
- Breaking Semantics For Physical Size Metrics
There are several follow-up work items planned.
Refer to the Epic issue on GitHub: https://github.com/neondatabase/neon/issues/2029
closes https://github.com/neondatabase/neon/pull/3013
Co-authored-by: Kirill Bulatov <kirill@neon.tech>
Co-authored-by: Christian Schwarz <christian@neon.tech>
New RemoteLayer Type
====================
Instead of downloading all layers during tenant attach, we create
RemoteLayer instances for each of them and add them to the layer map.
On-Demand Download As An Effect Of Page Reconstruction
======================================================
At the heart of pageserver is Timeline::get_reconstruct_data(). It
traverses the layer map until it has collected all the data it needs to
produce the page image. Most code in the code base uses it, though many
layers of indirection.
Before this patch, the function would use synchronous filesystem IO to
load data from disk-resident layer files if the data was not cached.
That is not possible with RemoteLayer, because the layer file has not
been downloaded yet. So, we do the download when get_reconstruct_data
gets there, i.e., “on demand”.
The mechanics of how the download is done are rather involved, because
of the infamous async-sync-async sandwich problem that plagues the async
Rust world. We use the new PageReconstructResult type to work around
this. Its introduction is the cause for a good amount of code churn in
this patch. Refer to the block comment on `with_ondemand_download()`
for details.
Breaking Semantics For Physical Size Metrics
============================================
We rename prometheus metric pageserver_{current,resident}_physical_size to
reflect what this metric actually represents with on-demand download.
This intentionally BREAKS existing grafana dashboard and the cost model data
pipeline. Breaking is desirable because the meaning of this metrics has changed
with on-demand download. See
https://docs.google.com/document/d/12AFpvKY-7FZdR5a4CaD6Ir_rI3QokdCLSPJ6upHxJBo/edit#
for how we will handle this breakage.
Likewise, we rename the new billing_metrics’s PhysicalSize => ResidentSize.
This is not yet used anywhere, so, this is not a breaking change.
There is still a field called TimelineInfo::current_physical_size. It
is now the sum of the layer sizes in layer map, regardless of whether
local or remote. To compute that sum, we added a new trait method
PersistentLayer::file_size().
When updating the Python tests, we got rid of
current_physical_size_non_incremental. An earlier commit removed it from
the OpenAPI spec already, so this is not a breaking change.
test_timeline_size.py has grown additional assertions on the
resident_physical_size metric.
Part of https://github.com/neondatabase/neon/pull/2239
Regular, from scratch, timeline creation involves initdb to be run in a separate directory, data from this directory to be imported into pageserver and, finally, timeline-related background tasks to start.
This PR ensures we don't leave behind any directories that are not marked as temporary and that pageserver removes such directories on restart, allowing timeline creation to be retried with the same IDs, if needed.
It would be good to later rewrite the logic to use a temporary directory, similar what tenant creation does.
Yet currently it's harder than this change, so not done.
- Split postgres_ffi into two version specific files.
- Preserve pg_version in timeline metadata.
- Use pg_version in safekeeper code. Check for postgres major version mismatch.
- Clean up the code to use DEFAULT_PG_VERSION constant everywhere, instead of hardcoding.
- Parameterize python tests: use DEFAULT_PG_VERSION env and pg_version fixture.
To run tests using a specific PostgreSQL version, pass the DEFAULT_PG_VERSION environment variable:
'DEFAULT_PG_VERSION='15' ./scripts/pytest test_runner/regress'
Currently don't all tests pass, because rust code relies on the default version of PostgreSQL in a few places.
Another preparatory commit for pg15 support:
* generate bindings for both pg14 and pg15;
* update Makefile and CI scripts: now neon build depends on both PostgreSQL versions;
* some code refactoring to decrease version-specific dependencies.
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.
Previously DatadirTimeline was a separate struct, and there was a 1:1
relationship between each DatadirTimeline and LayeredTimeline. That was
a bit awkward; whenever you created a timeline, you also needed to create
the DatadirTimeline wrapper around it, and if you only had a reference
to the LayeredTimeline, you would need to look up the corresponding
DatadirTimeline struct through tenant_mgr::get_local_timeline_with_load().
There were a couple of calls like that from LayeredTimeline itself.
Refactor DatadirTimeline, so that it's a trait, and mark LayeredTimeline
as implementing that trait. That way, there's only one object,
LayeredTimeline, and you can call both Timeline and DatadirTimeline
functions on that. You can now also call DatadirTimeline functions from
LayeredTimeline itself.
I considered just moving all the functions from DatadirTimeline directly
to Timeline/LayeredTimeline, but I still like to have some separation.
Timeline provides a simple key-value API, and handles durably storing
key/value pairs, and branching. Whereas DatadirTimeline is stateless, and
provides an abstraction over the key-value store, to present an interface
with relations, databases, etc. Postgres concepts.
This simplified the logical size calculation fast-path for branch
creation, introduced in commit 28243d68e6. LayerTimeline can now
access the ancestor's logical size directly, so it doesn't need the
caller to pass it to it. I moved the fast-path to init_logical_size()
function itself. It now checks if the ancestor's last LSN is the same
as the branch point, i.e. if there haven't been any changes on the
ancestor after the branch, and copies the size from there. An
additional bonus is that the optimization will now work any time you
have a branch of another branch, with no changes from the ancestor,
not only at a create-branch command.
## Overview
This patch reduces the number of memory allocations when running the page server under a heavy write workload. This mostly helps improve the speed of WAL record ingestion.
## Changes
- modified `DatadirModification` to allow reuse the struct's allocated memory after each modification
- modified `decode_wal_record` to allow passing a `DecodedWALRecord` reference. This helps reuse the struct in each `decode_wal_record` call
- added a reusable buffer for serializing object inside the `InMemoryLayer::put_value` function
- added a performance test simulating a heavy write workload for testing the changes in this patch
### Semi-related changes
- remove redundant serializations when calling `DeltaLayer::put_value` during `InMemoryLayer::write_to_disk` function call [1]
- removed the info span `info_span!("processing record", lsn = %lsn)` during each WAL ingestion [2]
## Notes
- [1]: in `InMemoryLayer::write_to_disk`, a deserialization is called
```
let val = Value::des(&buf)?;
delta_layer_writer.put_value(key, *lsn, val)?;
```
`DeltaLayer::put_value` then creates a serialization based on the previous deserialization
```
let off = self.blob_writer.write_blob(&Value::ser(&val)?)?;
```
- [2]: related: https://github.com/neondatabase/neon/issues/733
Before this patch, importing a physical backup followed the same path
as ingesting any WAL records:
1. All the data pages from the backup are first collected in the
DatadirModification object.
2. Then, they are "committed" to the Repository. They are written to
the in-memory layer
3. Finally, the in-memory layer is frozen, and flushed to disk as a
L0 delta layer file.
This was pretty inefficient. In step 1, the whole physical backup was
held in memory. If the backup is large, you simply run out of
memory. And in step 3, the resulting L0 delta layer file is large,
holding all the data again. That's a problem if the backup is larger
than 5 GB: Amazon S3 doesn't allow uploading files larger than 5 GB
(without using multi-part upload, see github issue #1910). So we want
to avoid that.
To alleviate those problems, optimize the codepath for importing a
physical backup. The basic flow is the same as before, but step 1
is optimized so that it doesn't accumulate all the data in memory,
and step 3 writes the data in image layers instead of one large delta
layer.
This is a backwards-incompatible change. The new pageserver cannot
read repositories created with an old pageserver binary, or vice
versa.
Simplify Repository to a value-store
------------------------------------
Move the responsibility of tracking relation metadata, like which
relations exist and what are their sizes, from Repository to a new
module, pgdatadir_mapping.rs. The interface to Repository is now a
simple key-value PUT/GET operations.
It's still not any old key-value store though. A Repository is still
responsible from handling branching, and every GET operation comes
with an LSN.
Mapping from Postgres data directory to keys/values
---------------------------------------------------
All the data is now stored in the key-value store. The
'pgdatadir_mapping.rs' module handles mapping from PostgreSQL objects
like relation pages and SLRUs, to key-value pairs.
The key to the Repository key-value store is a Key struct, which
consists of a few integer fields. It's wide enough to store a full
RelFileNode, fork and block number, and to distinguish those from
metadata keys.
'pgdatadir_mapping.rs' is also responsible for maintaining a
"partitioning" of the keyspace. Partitioning means splitting the
keyspace so that each partition holds a roughly equal number of keys.
The partitioning is used when new image layer files are created, so
that each image layer file is roughly the same size.
The partitioning is also responsible for reclaiming space used by
deleted keys. The Repository implementation doesn't have any explicit
support for deleting keys. Instead, the deleted keys are simply
omitted from the partitioning, and when a new image layer is created,
the omitted keys are not copied over to the new image layer. We might
want to implement tombstone keys in the future, to reclaim space
faster, but this will work for now.
Changes to low-level layer file code
------------------------------------
The concept of a "segment" is gone. Each layer file can now store an
arbitrary range of Keys.
Checkpointing, compaction
-------------------------
The background tasks are somewhat different now. Whenever
checkpoint_distance is reached, the WAL receiver thread "freezes" the
current in-memory layer, and creates a new one. This is a quick
operation and doesn't perform any I/O yet. It then launches a
background "layer flushing thread" to write the frozen layer to disk,
as a new L0 delta layer. This mechanism takes care of durability. It
replaces the checkpointing thread.
Compaction is a new background operation that takes a bunch of L0
delta layers, and reshuffles the data in them. It runs in a separate
compaction thread.
Deployment
----------
This also contains changes to the ansible scripts that enable having
multiple different pageservers running at the same time in the staging
environment. We will use that to keep an old version of the pageserver
running, for clusters created with the old version, at the same time
with a new pageserver with the new binary.
Author: Heikki Linnakangas
Author: Konstantin Knizhnik <knizhnik@zenith.tech>
Author: Andrey Taranik <andrey@zenith.tech>
Reviewed-by: Matthias Van De Meent <matthias@zenith.tech>
Reviewed-by: Bojan Serafimov <bojan@zenith.tech>
Reviewed-by: Konstantin Knizhnik <knizhnik@zenith.tech>
Reviewed-by: Anton Shyrabokau <antons@zenith.tech>
Reviewed-by: Dhammika Pathirana <dham@zenith.tech>
Reviewed-by: Kirill Bulatov <kirill@zenith.tech>
Reviewed-by: Anastasia Lubennikova <anastasia@zenith.tech>
Reviewed-by: Alexey Kondratov <alexey@zenith.tech>
