public inbox for [email protected]
help / color / mirror / Atom feedFrom: PG Bug reporting form <[email protected]>
To: [email protected]
Cc: [email protected]
Subject: BUG #19430: Autovacuums stopped working possible due to problem with vacuuming shared catalog pg_authid
Date: Thu, 12 Mar 2026 09:24:21 +0000
Message-ID: <[email protected]> (raw)
The following bug has been logged on the website:
Bug reference: 19430
Logged by: Alexey Ermakov
Email address: [email protected]
PostgreSQL version: 14.15
Operating system: Ubuntu 22.04
Description:
On a PostgreSQL 14.15 server with about 100 databases running on Ubuntu
22.04 I observed following problem:
1) According to the DB logs (log_autovacuum_min_duration = 1s) and
monitoring graphs autovacuums almost completely stopped working across all
DBs at once
2) This is also confirmed by checking pg_stat_user_tables.last_autovacuum in
all databases, there were no autovacuums anywhere for several days
3) Counters in pg_stat_user_tables updated normally, no anomalies there
4) pg_stat_all_tables.last_autovacuum shows one anomaly with pg_authid
catalog: only that catalog was autovacuumed recently (there are not many
dead rows there, looks normal). There might be other anomalies in other
databases as I only checked one but I doubt it.
5) I found nothing interesting in the logs around the time when problem
started (I checked for ERROR/WARNING/FATAL messages and possible DDL queries
but sadly log_statement = none there, log_min_duration_statement = 1s)
6) Autovacuum launcher process appears to be running normally, periodically
wakes up and consume 1-3% CPU of single core, pg_stat_activity shows the
wait event as AutoVacuumMain
7) Just in case, I checked dmesg entries and the time offset graph in
monitoring (to verify that time wasn't moving backwards for some reason) -
no anomalies there
8) Running vacuum on one of the bloated tables (which cause performance
problems) worked without issues
9) There is no long running transactions or lagging standbys with
hot_standby_feedback on
10) pg_authid catalog has `age(relfrozenxid)` around 290M but
autovacuum_freeze_max_age is 200M and anti-wraparound autovacuum should've
been triggered
11) After running `vacuum verbose pg_authid;` nothing changed (it wasn't an
aggressive vacuum) but running `vacuum (freeze, verbose) pg_authid;` fixed
problem and autovacuums started working properly. Output of these commands
are at the end of the report.
I assume that problem might have started when age(relfrozenxid) for
pg_authid approached autovacuum_freeze_max_age. A rough estimate based on
the current rate of age(relfrozenxid) confirms that we might indeed did 90M
transactions during the autovacuum malfunction.
An interesting observation: the query `ALTER ROLE xxx WITH ;` from some
permission-granting business logic triggered several autovacuums on ~half of
databases at same second for some time but didn't fix the problem
completely. Perhaps some cache invalidation did that?
Unfortunately, 14.15 is more than 1 year old. An update to 14.22 was
discussed recently but haven't been made yet. There were several fixes
related to vacuum/autovacuum but they didn't seem directly related to the
issue but I might be wrong.
Output of vacuum commands:
vacuum verbose pg_authid;
INFO: vacuuming "pg_catalog.pg_authid"
INFO: table "pg_authid": found 0 removable, 7 nonremovable row versions in
1 out of 57 pages
DETAIL: 0 dead row versions cannot be removed yet, oldest xmin: 3828262030
Skipped 0 pages due to buffer pins, 55 frozen pages.
CPU: user: 0.00 s, system: 0.00 s, elapsed: 0.00 s.
INFO: vacuuming "pg_toast.pg_toast_1260"
INFO: table "pg_toast_1260": found 0 removable, 0 nonremovable row versions
in 0 out of 0 pages
DETAIL: 0 dead row versions cannot be removed yet, oldest xmin: 3828262030
Skipped 0 pages due to buffer pins, 0 frozen pages.
CPU: user: 0.00 s, system: 0.00 s, elapsed: 0.00 s.
VACUUM
vacuum (freeze, verbose) pg_authid;
INFO: aggressively vacuuming "pg_catalog.pg_authid"
INFO: table "pg_authid": found 0 removable, 196 nonremovable row versions
in 4 out of 57 pages
DETAIL: 0 dead row versions cannot be removed yet, oldest xmin: 3828278683
Skipped 0 pages due to buffer pins, 53 frozen pages.
CPU: user: 0.00 s, system: 0.00 s, elapsed: 0.00 s.
INFO: aggressively vacuuming "pg_toast.pg_toast_1260"
INFO: table "pg_toast_1260": found 0 removable, 0 nonremovable row versions
in 0 out of 0 pages
DETAIL: 0 dead row versions cannot be removed yet, oldest xmin: 3828278683
Skipped 0 pages due to buffer pins, 0 frozen pages.
CPU: user: 0.00 s, system: 0.00 s, elapsed: 0.00 s.
VACUUM
Thanks,
Alexey Ermakov
view thread (2+ messages) latest in thread
reply
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Reply to all the recipients using the --to and --cc options:
reply via email
To: [email protected]
Cc: [email protected], [email protected], [email protected]
Subject: Re: BUG #19430: Autovacuums stopped working possible due to problem with vacuuming shared catalog pg_authid
In-Reply-To: <[email protected]>
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
This inbox is served by agora; see mirroring instructions
for how to clone and mirror all data and code used for this inbox