Horton

Re: prevent immature WAL streaming

Tom Lane <tgl@sss.pgh.pa.us>

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Alvaro Herrera <alvherre@alvh.no-ip.org>
Cc: Andres Freund <andres@anarazel.de>, Andrew Dunstan <andrew@dunslane.net>, "Bossart, Nathan" <bossartn@amazon.com>, Kyotaro Horiguchi <horikyota.ntt@gmail.com>, "masao.fujii@oss.nttdata.com" <masao.fujii@oss.nttdata.com>, "pgsql-hackers@lists.postgresql.org" <pgsql-hackers@lists.postgresql.org>, "mengjuan.cmj@alibaba-inc.com" <mengjuan.cmj@alibaba-inc.com>, "Jakub.Wartak@tomtom.com" <Jakub.Wartak@tomtom.com>, Ryo Matsumura <matsumura.ryo@fujitsu.com>
Date: 2021-11-09T23:08:07Z
Lists: pgsql-hackers 
I wrote:
> Seems like this hasn't fixed the problem: skink still fails on
> this test occasionally.
> #   Failed test '000000010000000000000002 differs from 000000010000000000000002'
> #   at t/026_overwrite_contrecord.pl line 61.

This is still happening off and on, which makes it look like a
timing-sensitive problem.  Confirming that, I can make it fail
every time by adding a long sleep just ahead of where
026_overwrite_contrecord.pl captures $initfile.  On reflection
I think the problem is obvious: if autovacuum does anything
concurrently with the test's startup portion, it will cause the
carefully-established WAL insertion point to move into the
next segment.  I propose to add "autovacuum = off" to the
test's postmaster configuration.

Also, I think we want

-ok($initfile != $endfile, "$initfile differs from $endfile");
+ok($initfile ne $endfile, "$initfile differs from $endfile");

The existing coding works as long as all characters of these
WAL segment names happen to be decimal digits, but ...

			regards, tom lane

Commits

  1. Fix determination of broken LSN in OVERWRITTEN_CONTRECORD

  2. Fix instability in 026_overwrite_contrecord.pl test.

  3. Fix typo

  4. Change recently added test code for stability

  5. Remove unstable, unnecessary test; fix typo

  6. Repair two portability oversights of new test

  7. Fix WAL replay in presence of an incomplete record

  8. Document XLOG_INCLUDE_XID a little better

  9. Revert "Avoid creating archive status ".ready" files too early"

  10. Avoid creating archive status ".ready" files too early

  11. Fix scenario where streaming standby gets stuck at a continuation record.

  12. Teach xlogreader to follow timeline switches

  13. Forbid using pg_xlogfile_name() and pg_xlogfile_name_offset() during