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Re: Hot Standby query cancellation and Streaming Replication integration

From: Dimitri Fontaine <dfontaine(at)hi-media(dot)com>
To: Bruce Momjian <bruce(at)momjian(dot)us>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Greg Stark <gsstark(at)mit(dot)edu>, Josh Berkus <josh(at)agliodbs(dot)com>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: Hot Standby query cancellation and Streaming Replication integration
Date: 2010-02-26 22:11:28
Message-ID: m2iq9jtzov.fsf@hi-media.com (view raw or flat)
Thread:
Lists: pgsql-hackers
Bruce Momjian <bruce(at)momjian(dot)us> writes:
> Doesn't the system already adjust the delay based on the length of slave
> transactions, e.g. max_standby_delay.  It seems there is no need for a
> user switch --- just max_standby_delay really high.

Well that GUC looks like it allows to set a compromise between HA and
reporting, not to say "do not ever give the priority to the replay while
I'm running my reports". At least that's how I understand it.

The feedback loop might get expensive on master server when running
reporting queries on the slave, unless you can "pause" it explicitly I
think. I don't see how the system will guess that you're running a
reporting server rather than a HA node, and max_standby_delay is just a
way to tell the standby to please be nice in case of abuse.

Regards,
-- 
dim

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Next:From: Bruce MomjianDate: 2010-02-26 22:20:37
Subject: Re: Hot Standby query cancellation and Streaming Replication integration
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