Date: Mon, 08 Nov 2021 14:59:46 +0900 (JST)
Message-Id: <20211108.145946.1513355777186578917.horikyota.ntt@gmail.com>
To: bossartn@amazon.com
Cc: david@pgmasters.net, peter.eisentraut@2ndquadrant.com,
 andres@anarazel.de, michael@paquier.xyz,
 pgsql-hackers@lists.postgresql.org, jtc331@gmail.com, robertmhaas@gmail.com
Subject: Re: Make mesage at end-of-recovery less scary.
From: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
In-Reply-To: <DD96F20D-1118-4C8E-8B04-D1F50320B0C7@amazon.com>
References: <b432bad3-e379-8a3a-6a35-1d47c116f2de@pgmasters.net>
	<20210304.155039.2020434514871976864.horikyota.ntt@gmail.com>
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At Fri, 22 Oct 2021 17:54:40 +0000, "Bossart, Nathan" <bossartn@amazon.com> wrote in 
> On 3/4/21, 10:50 PM, "Kyotaro Horiguchi" <horikyota.ntt@gmail.com> wrote:
> > As the result, the following messages are emitted with the attached.
> 
> I'd like to voice my support for this effort, and I intend to help
> review the patch.  It looks like the latest patch no longer applies,
> so I've marked the commitfest entry [0] as waiting-on-author.
> 
> Nathan
> 
> [0] https://commitfest.postgresql.org/35/2490/

Sorry for being late to reply.  I rebased this to the current master.

- rebased

- use LSN_FORMAT_ARGS instead of bare shift and mask.

- v4 immediately exited walreceiver on disconnection. Maybe I wanted
  not to see a FATAL message on standby after primary dies. However
  that would be another issue and that change was plain wrong..  v5
  just removes the "end-of-WAL" part from the message, which duplicate
  to what startup emits.

- add a new error message "missing contrecord at %X/%X".  Maybe this
  should be regarded as a leftover of the contrecord patch. In the
  attached patch the "%X/%X" is the LSN of the current record. The log
  messages look like this (026_overwrite_contrecord).

LOG:  redo starts at 0/1486CB8
WARNING:  missing contrecord at 0/1FFC2E0
LOG:  consistent recovery state reached at 0/1FFC2E0
LOG:  started streaming WAL from primary at 0/2000000 on timeline 1
LOG:  successfully skipped missing contrecord at 0/1FFC2E0, overwritten at 2021-11-08 14:50:11.969952+09
CONTEXT:  WAL redo at 0/2000028 for XLOG/OVERWRITE_CONTRECORD: lsn 0/1FFC2E0; time 2021-11-08 14:50:11.969952+09

While checking the behavior for the case of missing-contrecord, I
noticed that emode_for_corrupt_record() doesn't work as expected since
readSource is reset to XLOG_FROM_ANY after a read failure. We could
remember the last failed source but pg_wal should have been visited if
page read error happened so I changed the function so that it treats
XLOG_FROM_ANY the same way with XLOG_FROM_PG_WAL.

(Otherwise we see "LOG: reached end-of-WAL at .." message after
 "WARNING: missing contrecord at.." message.)

regards.

-- 
Kyotaro Horiguchi
NTT Open Source Software Center

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