Horton

Re: Race condition in recovery?

Kyotaro Horiguchi <horikyota.ntt@gmail.com>

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From: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
To: tatsuro.yamada.tf@nttcom.co.jp
Cc: robertmhaas@gmail.com, dilipbalaut@gmail.com, pgsql-hackers@lists.postgresql.org, hlinnaka@iki.fi
Date: 2021-05-28T07:40:49Z
Lists: pgsql-hackers 
(Sorry for being a bit off-topic)

At Fri, 28 May 2021 12:18:35 +0900, Tatsuro Yamada <tatsuro.yamada.tf@nttcom.co.jp> wrote in 
> Hi Horiguchi-san,

(Why me?)

> In a project I helped with, I encountered an issue where
> the archive command kept failing. I thought this issue was
> related to the problem in this thread, so I'm sharing it here.
> If I should create a new thread, please let me know.
> 
> * Problem
>   - The archive_command is failed always.

Although I think the configuration is a kind of broken, it can be seen
as it is mimicing the case of shared-archive, where primary and
standby share the same archive directory.

Basically we need to use an archive command like the following for
that case to avoid this kind of failure. The script returns "success"
when the target file is found but identical with the source file. I
don't find such a description in the documentation, and haven't
bothered digging into the mailing-list archive.

==
#! /bin/bash

if [ -f $2 ]; then
	cmp -s $1 $2
	if [ $? != 0 ]; then
		exit 1
	fi
	exit 0
fi

cp $1 $2
==

A maybe-non-optimal behavior is both 00000002.history.done and .ready
files are found at once in archive_status directory but that doesn't
practically matter. (Or I faintly remember that it is designed to work
even in that case.)

regards.

-- 
Kyotaro Horiguchi
NTT Open Source Software Center

Commits

  1. Further refinement of stuck_on_old_timeline recovery test

  2. Adjust new test case to set wal_keep_segments.

  3. Adjust new test case to set wal_keep_size.

  4. Fix corner case failure of new standby to follow new primary.

  5. Back-port a few PostgresNode.pm methods.

  6. Allow PostgresNode.pm's backup method to accept backup_options.

  7. Add end-to-end testing of pg_basebackup's tar-format output.

  8. Allow PostgresNode.pm tests to wait for catchup

  9. Delay reading timeline history file until it's fetched from master.