From: Tom Lane <tgl@sss.pgh.pa.us>
To: Noah Misch <noah@leadboat.com>
Cc: Michael Paquier <michael@paquier.xyz>
Cc: pgsql-hackers@postgresql.org
Subject: Re: XLogReadRecord() error in XlogReadTwoPhaseData()
Date: Wed, 17 Nov 2021 17:47:10 -0500
Message-ID: <2782601.1637189230@sss.pgh.pa.us> (raw)
In-Reply-To: <20211112012234.GA1020314@rfd.leadboat.com>
References: <20211107013157.GB790288@rfd.leadboat.com>
<YYiqxtEqhgb5gIWL@paquier.xyz>
<20211112012234.GA1020314@rfd.leadboat.com>
Noah Misch <noah@leadboat.com> writes:
> Tom Lane reported another instance today:
> https://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=tadarida&dt=2021-11-11%2013%3A29%3A58> Each of the three failures happened on a sparc64 Debian+gcc machine. I had
> tried ~8000 iterations on thorntail, another sparc64 Debian+gcc animal,
> without reproducing this.
>>> As a first step, let's report the actual XLogReadRecord() error message.
>>> Attached.
>> Good catch! This looks good.
> Pushed.
Well, we didn't have to wait too long [1]:
# at t/003_cic_2pc.pl line 143.
# 'pgbench: error: client 0 script 1 aborted in command 4 query 0: ERROR: could not read two-phase state from WAL at 0/159EF88: unexpected pageaddr 0/0 in log segment 000000010000000000000001, offset 5890048
# pgbench: error: client 2 script 3 aborted in command 2 query 0: ERROR: canceling statement due to lock timeout
# pgbench: fatal: Run was aborted; the above results are incomplete.
I suppose "unexpected pageaddr 0/0" is most easily explained by supposing
that XlogReadTwoPhaseData tried to read a WAL page that hadn't been
written out yet. Have we got any synchronization around that?
regards, tom lane
[1] https://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=tadarida&dt=2021-11-17%2013%3A01%3A24
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To: pgsql-hackers@postgresql.org
Cc: tgl@sss.pgh.pa.us, noah@leadboat.com, michael@paquier.xyz
Subject: Re: XLogReadRecord() error in XlogReadTwoPhaseData()
In-Reply-To: <2782601.1637189230@sss.pgh.pa.us>
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