Subject: Re: pgsql: Add support for temporary replication slots
To: Tom Lane <tgl@sss.pgh.pa.us>, Peter Eisentraut <peter_e@gmx.net>
References: <E1cGRP8-0003EH-So@gemulon.postgresql.org>
 <27274.1481557380@sss.pgh.pa.us> <27833.1481558144@sss.pgh.pa.us>
Cc: pgsql-committers@postgresql.org
From: Petr Jelinek <petr.jelinek@2ndquadrant.com>
Message-ID: <62935e6f-4f1b-c433-e0fa-7f936a38b3e5@2ndquadrant.com>
Date: Mon, 12 Dec 2016 19:47:53 +0100
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On 12/12/16 16:55, Tom Lane wrote:
> I wrote:
>> Peter Eisentraut <peter_e@gmx.net> writes:
>>> Add support for temporary replication slots
> 
>> Some of the slower buildfarm members are failing test-decoding-check since
>> this went in.  At least on prairiedog, it looks like a race condition in
>> the test:
> 
> Having now looked a bit more closely, that's almost certainly what it is:
> the test is assuming that the old backend exits instantaneously, which
> it doesn't.  You might want to borrow the wait-for-previous-session-to-die
> loop I put into src/test/modules/test_extensions/sql/test_extensions.sql
> recently.  (Make sure you get the fixed version ;-))
> 

Yes you are correct, we tried naively to first drop another slot in
hopes that it will give the other backend enough time to close, but
apparently that wasn't robust enough for slower machines.

Attached is the fixed test using the loop from test_extensions (and yes
I would have missed the pg_stat_clear_snapshot() call without the hint,
thanks :) ).

-- 
  Petr Jelinek                  http://www.2ndQuadrant.com/
  PostgreSQL Development, 24x7 Support, Training & Services

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