Re: Hot standby v5 patch assertion failure

From: Mark Kirkwood <markir(at)paradise(dot)net(dot)nz>
To: Simon Riggs <simon(at)2ndQuadrant(dot)com>
Cc: pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Hot standby v5 patch assertion failure
Date: 2008-11-09 22:07:57
Message-ID: 49175F3D.2010000@paradise.net.nz
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Simon Riggs wrote:
> On Mon, 2008-11-03 at 12:16 +1300, Mark Kirkwood wrote:
>
>> Trying out a few different scenarios I ran across this:
>>
>> 1/ Setup master and replica with replica using pg_standby
>> 2/ Create a new database ("bench" in my case)
>> 3/ Initialize pgbench schema size 100
>> 4/ Run with 2 clients and 10000 transactions
>> 5/ Replica gets assertion failure
>>
>
> I've been unable to reproduce this error in more than 2 days of bashing.
> The bash test I use is a pgbench variant designed to cause write
> contention, while at the same time running reads against those same
> blocks on standby, plus running parallel installcheck.
>
> I suspect now there was a problem in ProcArrayClearUnobservedXids(), so
> I clear the array each time now, whether or not we are in assert mode.
> i.e. better hygiene around reused data structures. So I *haven't*
> reworked my earlier code, just checked it all again.
>
> So, new patch enclosed. This fixes everything reported so far, plus
> another 2 bugs I found and fixed during re-test.
>
>
Patching with v5d, I can no longer reproduce this either. Excellent!

Cheers

Mark

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