Re: Time-Delayed Standbys

From: Simon Riggs <simon(at)2ndQuadrant(dot)com>
To: Andres Freund <andres(at)2ndquadrant(dot)com>
Cc: Fabrízio Mello <fabriziomello(at)gmail(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, KONDO Mitsumasa <kondo(dot)mitsumasa(at)lab(dot)ntt(dot)co(dot)jp>, Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>, Pgsql Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Time-Delayed Standbys
Date: 2013-12-13 13:09:13
Message-ID: CA+U5nMLRgEqvjyNnWGEO3pwAafBybtmvF6++OqDQHSasdnSqPg@mail.gmail.com
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On 13 December 2013 11:58, Andres Freund <andres(at)2ndquadrant(dot)com> wrote:
> On 2013-12-13 11:56:47 +0000, Simon Riggs wrote:
>> On 12 December 2013 21:58, Fabrízio de Royes Mello
>> <fabriziomello(at)gmail(dot)com> wrote:
>> > Reviewing the committed patch I noted that the "CheckForStandbyTrigger()"
>> > after the delay was removed.
>> >
>> > If we promote the standby during the delay and don't check the trigger
>> > immediately after the delay, then we will replay undesired WALs records.
>> >
>> > The attached patch add this check.
>>
>> I removed it because it was after the pause. I'll replace it, but
>> before the pause.
>
> Doesn't after the pause make more sense? If somebody promoted while we
> were waiting, we want to recognize that before rolling forward? The wait
> can take a long while after all?

That would change the way pause currently works, which is OOS for that patch.

I'm happy to discuss such a change, but if agreed, it would need to
apply in all cases, not just this one.

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

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