From: PG Bug reporting form <noreply@postgresql.org>
To: pgsql-bugs@lists.postgresql.org
Cc: dkorzunov@symmetryinvestments.com
Subject: BUG #18417: Excessive log messages on warm standby server
Date: Fri, 29 Mar 2024 04:44:27 +0000
Message-ID: <18417-174d6d30bfbedda3@postgresql.org> (raw)
The following bug has been logged on the website:
Bug reference: 18417
Logged by: Denis Korzunov
Email address: dkorzunov@symmetryinvestments.com
PostgreSQL version: 16.2
Operating system: Debian Bullseye
Description:
I have log-shipping replication set up. The master server generates archive
files which are then sent to a remote location where replica server reads
them and applies changes.
The nature of the application is that writes occur in batches, large volumes
but infrequently, a few times per day.
The warm standby server generates the following messages every
wal_retrieve_retry_interval, which is 5 seconds by default:
2024-03-29 04:30:25.436 UTC [35160] LOG: waiting for WAL to become
available at 0/5000018
2024-03-29 04:30:30.441 UTC [35160] LOG: waiting for WAL to become
available at 0/5000018
2024-03-29 04:30:35.443 UTC [35160] LOG: waiting for WAL to become
available at 0/5000018
2024-03-29 04:30:40.448 UTC [35160] LOG: waiting for WAL to become
available at 0/5000018
2024-03-29 04:30:45.449 UTC [35160] LOG: waiting for WAL to become
available at 0/5000018
There were no such messages in PostgreSQL 14. From what I can tell, it
first appeared in PostgresQL 15 and continued in 16.
I did a bit of digging in the source code and in PostgreSQL 14 the
WaitForWALToBecomeAvailable (xlog.c) function[1] didn't have the code to log
such message, however starting from PostgresSQL 15 the function has been
moved to xlogrecovery.c[2] and contains the statement:
elog(LOG, "waiting for WAL to become available at %X/%X",
LSN_FORMAT_ARGS(RecPtr));
The problem is that the log level here is set to LOG and to turn the message
off I have to set log_min_messages to "fatal" which cuts off many useful
messages I'd prefer to keep in the log file.
The relevant configuration parameters are:
log_min_messages = info
archive_mode = on
archive_command = 'test ! -f /archive/%f && zstd --quiet %p -o
/archive/tmp/%f && mv /archive/tmp/%f /archive/%f'
archive_timeout = 30
restore_command = 'test -f /archive/%f && zstd --quiet --decompress
/archive/%f -o /archive/tmp/%f && mv /archive/tmp/%f %p'
Links to source code:
[1]
https://github.com/postgres/postgres/blob/REL_14_STABLE/src/backend/access/transam/xlog.c#L12761
[2]
https://github.com/postgres/postgres/blob/master/src/backend/access/transam/xlogrecovery.c#L3690
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To: pgsql-bugs@postgresql.org
Cc: noreply@postgresql.org, pgsql-bugs@lists.postgresql.org, dkorzunov@symmetryinvestments.com
Subject: Re: BUG #18417: Excessive log messages on warm standby server
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