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Re: Hot Standby Lagging Behind

From: Lonni J Friedman <netllama(at)gmail(dot)com>
To: Prima Chairunnanda <prima(dot)ch(at)gmail(dot)com>
Cc: pgsql-novice(at)postgresql(dot)org
Subject: Re: Hot Standby Lagging Behind
Date: 2012-08-25 18:33:20
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Lists: pgsql-novice
Are both servers identical hardware?

On Sat, Aug 25, 2012 at 12:37 AM, Prima Chairunnanda <prima(dot)ch(at)gmail(dot)com> wrote:
> Hi Everyone,
> I have some questions about the PostgreSQL streaming replication feature. I
> have been able to setup a hot-standby server, and I can see updates on the
> master server being replayed on the standby server.
> However I notice that once I start making read-only queries, the standby
> starts lagging behind the master server. After a while, the delay can reach
> over 1 minute, even though I set the max_standby_streaming_delay parameter
> to 15s. I am under the impression that once a WAL record is lagging 15s
> behind, then it should trump any read-only queries in the system.
> Below are the values of pg_last_xlog_receive_location and
> pg_last_xlog_replay_location at several time points
>  now 03:06:16
>  pg_last_xlog_receive_location  0/59A31620
>  pg_last_xlog_replay_location  0/599A6B90
>  now 03:07:18
>  pg_last_xlog_receive_location 0/59A98460
>  pg_last_xlog_replay_location 0/59A1BE58
>  now 03:07:31
>  pg_last_xlog_receive_location 0/59AA8F48
>  pg_last_xlog_replay_location 0/59A22288
> So as we can see the WAL record at 0/59A31620 was received at 03:06:16, but
> more than a minute later at 03:07:31, it still hasn't been replayed.
> Am I configuring the wrong thing? Is there an option to increase the
> priority of the WAL replay once it has been lagging for a certain amount of
> WAL record?
> Thanks in advance for your help.
> Prima

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