We have one pretty serious MVCC visibility bug with hot standby
replicas. We incorrectly treat any transactions that are in progress
in the primary, when the standby is started, as aborted. That can
break MVCC for queries running concurrently in the standby. It can
also lead to hint bits being set incorrectly, and that damage can last
until the replica is restarted.
The fundamental bug was that we treated any replica start as starting
from a shut down server. The fix for that is straightforward: we need
to set 'wasShutdown = false' in InitWalRecovery() (see changes in the
postgres repo).
However, that introduces a new problem: with wasShutdown = false, the
standby will not open up for queries until it receives a running-xacts
WAL record from the primary. That's correct, and that's how Postgres
hot standby always works. But it's a problem for Neon, because:
* It changes the historical behavior for existing users. Currently,
the standby immediately opens up for queries, so if they now need to
wait, we can breka existing use cases that were working fine
(assuming you don't hit the MVCC issues).
* The problem is much worse for Neon than it is for standalone
PostgreSQL, because in Neon, we can start a replica from an
arbitrary LSN. In standalone PostgreSQL, the replica always starts
WAL replay from a checkpoint record, and the primary arranges things
so that there is always a running-xacts record soon after each
checkpoint record. You can still hit this issue with PostgreSQL if
you have a transaction with lots of subtransactions running in the
primary, but it's pretty rare in practice.
To mitigate that, we introduce another way to collect the
running-xacts information at startup, without waiting for the
running-xacts WAL record: We can the CLOG for XIDs that haven't been
marked as committed or aborted. It has limitations with
subtransactions too, but should mitigate the problem for most users.
See https://github.com/neondatabase/neon/issues/7236.
Co-authored-by: Konstantin Knizhnik <knizhnik@neon.tech>
We did not recover the subtransaction IDs of prepared transactions when
starting a hot standby from a shutdown checkpoint. As a result, such
subtransactions were considered as aborted, rather than in-progress.
That would lead to hint bits being set incorrectly, and the
subtransactions suddenly becoming visible to old snapshots when the
prepared transaction was committed.
To fix, update pg_subtrans with prepared transactions's subxids when
starting hot standby from a shutdown checkpoint. The snapshots taken
from that state need to be marked as "suboverflowed", so that we also
check the pg_subtrans.
Discussion:
https://www.postgresql.org/message-id/6b852e98-2d49-4ca1-9e95-db419a2696e0%40iki.fi
NEON: cherry-picked from the upstream thread ahead of time, to unblock
https://github.com/neondatabase/neon/pull/7288. I expect this to be
committed to upstream in the next few days, superseding this. NOTE: I
did not include the new regression test on v15 and v14 branches, because
the test would need some adapting, and we don't run the perl tests on
Neon anyway.
## Problem
See https://github.com/neondatabase/cloud/issues/10845
## Summary of changes
Do not report error if GIN page is not restored
## 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>
Using InvalidateBuffer is wrong, because if the page is concurrently
dirtied, it will throw away the dirty page without calling
smgwrite(). In Neon, that means that the last-written LSN update for
the page is missed.
In v16, use the new InvalidateVictimBuffer() function that does what
we need. In v15 and v14, backport the InvalidateVictimBuffer()
function.
Fixes issue https://github.com/neondatabase/neon/issues/7802
## Problem
Ref https://neondb.slack.com/archives/C036U0GRMRB/p1688122168477729
## Summary of changes
- Add sha from postgres repo into postgres version string (via
`--with-extra-version`)
- Add a test that Postgres version matches the expected one
- Remove build-time hard check and allow only related tests to fail
## Problem
See https://neondb.slack.com/archives/C03QLRH7PPD/p1712529369520409
In case of statements CREATE TABLE AS SELECT... or INSERT FROM SELECT...
we are fetching data from source table and storing it in destination
table. It cause problems with prefetch last-written-lsn is known for the
pages of source table
(which for example happens after compute restart). In this case we get
get global value of last-written-lsn which is changed frequently as far
as we are writing pages of destination table. As a result request-isn
for the prefetch and request-let when this page is actually needed are
different and we got exported prefetch request. So it actually disarms
prefetch.
## Summary of changes
Proposed simple patch stores last-written LSN for the page when it is
not found. So next time we will request last-written LSN for this page,
we will get the same value (certainly if the page was not changed).
## 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>
The walproposer pretends to be a walsender in many ways. It has a
WalSnd slot, it claims to be a walsender by calling
MarkPostmasterChildWalSender() etc. But one different to real
walsenders was that the postmaster still treated it as a bgworker
rather than a walsender. The difference is that at shutdown,
walsenders are not killed until the very end, after the checkpointer
process has written the shutdown checkpoint and exited.
As a result, the walproposer always got killed before the shutdown
checkpoint was written, so the shutdown checkpoint never made it to
safekeepers. That's fine in principle, we don't require a clean
shutdown after all. But it also feels a bit silly not to stream the
shutdown checkpoint. It could be useful for initializing hot standby
mode in a read replica, for example.
Change postmaster to treat background workers that have called
MarkPostmasterChildWalSender() as walsenders. That unfortunately
requires another small change in postgres core.
After doing that, walproposers stay alive longer. However, it also
means that the checkpointer will wait for the walproposer to switch to
WALSNDSTATE_STOPPING state, when the checkpointer sends the
PROCSIG_WALSND_INIT_STOPPING signal. We don't have the machinery in
walproposer to receive and handle that signal reliably. Instead, we
mark walproposer as being in WALSNDSTATE_STOPPING always.
In commit 568f91420a, I assumed that shutdown will wait for all the
remaining WAL to be streamed to safekeepers, but before this commit
that was not true, and the test became flaky. This should make it
stable again.
Some tests wrongly assumed that no WAL could have been written between
pg_current_wal_flush_lsn and quick pg stop after it. Fix them by introducing
flush_ep_to_pageserver which first stops the endpoint and then waits till all
committed WAL reaches the pageserver.
In passing extract safekeeper http client to its own module.
## Problem
LFC has high impact on Neon application performance but there is no way
for user to check efficiency of its usage
## Summary of changes
Show LFC statistic in EXPLAIN ANALYZE
## Description
**Local file cache (LFC)**
A layer of caching that stores frequently accessed data from the storage
layer in the local memory of the Neon compute instance. This cache helps
to reduce latency and improve query performance by minimizing the need
to fetch data from the storage layer repeatedly.
**Externalization of LFC in explain output**
Then EXPLAIN ANALYZE output is extended to display important counts for
local file cache (LFC) hits and misses.
This works both, for EXPLAIN text and json output.
**File cache: hits**
Whenever the Postgres backend retrieves a page/block from SGMR, it is
not found in shared buffer but the page is already found in the LFC this
counter is incremented.
**File cache: misses**
Whenever the Postgres backend retrieves a page/block from SGMR, it is
not found in shared buffer and also not in then LFC but the page is
retrieved from Neon storage (page server) this counter is incremented.
Example (for explain text output)
```sql
explain (analyze,buffers,prefetch,filecache) select count(*) from pgbench_accounts;
QUERY PLAN
--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Finalize Aggregate (cost=214486.94..214486.95 rows=1 width=8) (actual time=5195.378..5196.034 rows=1 loops=1)
Buffers: shared hit=178875 read=143691 dirtied=128597 written=127346
Prefetch: hits=0 misses=1865 expired=0 duplicates=0
File cache: hits=141826 misses=1865
-> Gather (cost=214486.73..214486.94 rows=2 width=8) (actual time=5195.366..5196.025 rows=3 loops=1)
Workers Planned: 2
Workers Launched: 2
Buffers: shared hit=178875 read=143691 dirtied=128597 written=127346
Prefetch: hits=0 misses=1865 expired=0 duplicates=0
File cache: hits=141826 misses=1865
-> Partial Aggregate (cost=213486.73..213486.74 rows=1 width=8) (actual time=5187.670..5187.670 rows=1 loops=3)
Buffers: shared hit=178875 read=143691 dirtied=128597 written=127346
Prefetch: hits=0 misses=1865 expired=0 duplicates=0
File cache: hits=141826 misses=1865
-> Parallel Index Only Scan using pgbench_accounts_pkey on pgbench_accounts (cost=0.43..203003.02 rows=4193481 width=0) (actual time=0.574..4928.995 rows=3333333 loops=3)
Heap Fetches: 3675286
Buffers: shared hit=178875 read=143691 dirtied=128597 written=127346
Prefetch: hits=0 misses=1865 expired=0 duplicates=0
File cache: hits=141826 misses=1865
```
The json output uses the following keys and provides integer values for
those keys:
```
...
"File Cache Hits": 141826,
"File Cache Misses": 1865
...
```
## 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 set it for neon replica, if primary is running.
Postgres uses this GUC at the start,
to determine if replica should wait for
RUNNING_XACTS from primary or not.
Corresponding cloud PR is
https://github.com/neondatabase/cloud/pull/10183
* Add test hot-standby replica startup.
* Extract oldest_running_xid from XlRunningXits WAL records.
---------
Co-authored-by: Konstantin Knizhnik <knizhnik@neon.tech>
Co-authored-by: Konstantin Knizhnik <knizhnik@garret.ru>
Co-authored-by: Heikki Linnakangas <heikki@neon.tech>
## Problem
See https://neondb.slack.com/archives/C04DGM6SMTM/p1708363190710839
## Summary of changes
Flush logical message with snapshot and origin state
## 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>
This reverts commit 9ad940086c.
This pull request reverts #6733 to avoid incompatibility with pgvector
and I will push further fixes later. Note that after reverting this pull
request, the postgres submodule will point to some detached branches.
close https://github.com/neondatabase/neon/issues/6236
This pull request bumps neon postgres dependencies. The corresponding
postgres commits fix the checks for superuser permission when creating
an extension. Also, for creating native functinos, it now allows
neon_superuser only in the extension creation process.
---------
Signed-off-by: Alex Chi Z <chi@neon.tech>
Co-authored-by: Heikki Linnakangas <heikki@neon.tech>
Cherry-pick Upstream commit fbf9a7ac4d to neon stable branches. We'll
get it in the next PostgreSQL minor release anyway, but we need it
now, if we want to start using the 'mmap' implementation.
See https://github.com/neondatabase/autoscaling/issues/800 for the
plans on doing that.
## Problem
See https://github.com/neondatabase/cloud/issues/8673
## Summary of changes
Download missed SLRU segments from 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
---------
Co-authored-by: Konstantin Knizhnik <knizhnik@neon.tech>
Co-authored-by: Heikki Linnakangas <heikki@neon.tech>
## Problem
We currently can't create subscriptions in PG14 and PG15 because only
superusers can, and PG16 requires adding roles to
pg_create_subscription.
## Summary of changes
I added changes to PG14 and PG15 that allow neon_superuser to bypass the
superuser requirement. For PG16, I didn't do that but added a migration
that adds neon_superuser to pg_create_subscription. Also added a test to
make sure it works.
## Problem
PG16 (https://github.com/neondatabase/postgres/pull/327) adds new
function to SMGR: zeroextend
It's implementation in Neon actually wal-log zero pages of extended
relation.
This zero page is wal-logged using XLOG_FPI.
As far as page is zero, the hole optimization (excluding from the image
everything between pg_upper and pd_lower) doesn't work.
## Summary of changes
In case of zero page (`PageIsNull()` returns true) assume
`hole_size=BLCKSZ`
## 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
See https://neondb.slack.com/archives/C04DGM6SMTM/p1698226491736459
## Summary of changes
Update WAL affected buffers when restoring WAL from safekeeper
## 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
Fix elog format error in wallog_mapping_file
## Summary of changes
Use proper case to avoid compilation warning=error in C at MacOS.
## 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
See https://github.com/neondatabase/company_projects/issues/111
## Summary of changes
Save logical replication files in WAL at compute and include them in
basebackup at pate 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
---------
Co-authored-by: Konstantin Knizhnik <knizhnik@neon.tech>
Co-authored-by: Arseny Sher <sher-ars@yandex.ru>
## 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>
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>
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>
## 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>
## 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
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>
This is prep for https://github.com/neondatabase/neon/pull/4255
[1/X] OpenAPI: share a single definition of TenantConfig
DRYs up the pageserver OpenAPI YAML's representation of
tenant config.
All the fields of tenant config are now located in a model schema
called TenantConfig.
The tenant create & config-change endpoints have separate schemas,
TenantCreateInfo and TenantConfigureArg, respectively.
These schemas inherit from TenantConfig, using allOf 1.
The tenant config-GET handler's response was previously named
TenantConfig.
It's now named TenantConfigResponse.
None of these changes affect how the request looks on the wire.
The generated Go code will change for Console because the OpenAPI code
generator maps `allOf` to a Go struct embedding.
Luckily, usage of tenant config in Console is still very lightweigt,
but that will change in the near future.
So, this is a good chance to set things straight.
The console changes are tracked in
https://github.com/neondatabase/cloud/pull/5046
[2/x]: extract the tenant config parts of create & config requests
[3/x]: code movement: move TenantConfigRequestConfig next to
TenantCreateRequestConfig
[4/x] type-alias TenantConfigRequestConfig = TenantCreateRequestConfig;
They are exactly the same.
[5/x] switch to qualified use for tenant create/config request api
models
[6/x] rename models::TenantConfig{RequestConfig,} and remove the alias
[7/x] OpenAPI: sync tenant create & configure body names from Rust code
[8/x]: dedupe the two TryFrom<...> for TenantConfOpt impls
The only difference is that the TenantConfigRequest impl does
```
tenant_conf.max_lsn_wal_lag = request_data.max_lsn_wal_lag;
tenant_conf.trace_read_requests = request_data.trace_read_requests;
```
and the TenantCreateRequest impl does
```
if let Some(max_lsn_wal_lag) = request_data.max_lsn_wal_lag {
tenant_conf.max_lsn_wal_lag = Some(max_lsn_wal_lag);
}
if let Some(trace_read_requests) = request_data.trace_read_requests {
tenant_conf.trace_read_requests = Some(trace_read_requests);
}
```
As far as I can tell, these are identical.
