From: | Magnus Hagander <magnus(at)hagander(dot)net> |
---|---|
To: | Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com> |
Cc: | Greg Smith <greg(at)2ndquadrant(dot)com>, Fujii Masao <masao(dot)fujii(at)gmail(dot)com>, Simon Riggs <simon(at)2ndquadrant(dot)com>, Josh Berkus <josh(at)agliodbs(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Streaming replication status |
Date: | 2010-01-12 10:18:45 |
Message-ID: | 9837222c1001120218x5584e0cfvef15c2e0fbd72949@mail.gmail.com |
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On Tue, Jan 12, 2010 at 08:22, Heikki Linnakangas
<heikki(dot)linnakangas(at)enterprisedb(dot)com> wrote:
> Greg Smith wrote:
>> I don't think anybody can deploy this feature without at least some very
>> basic monitoring here. I like the basic proposal you made back in
>> September for adding a pg_standbys_xlog_location to replace what you
>> have to get from ps right now:
>> http://archives.postgresql.org/pgsql-hackers/2009-09/msg00889.php
>>
>> That's basic, but enough that people could get by for a V1.
>
> It would be more straightforward to have a function in the standby to
> return the current replay location. It feels more logical to poll the
> standby to get the status of the standby, instead of indirectly from the
> master. Besides, the master won't know how far the standby is if the
> connection to the standby is broken.
>
> Maybe we should just change the existing pg_current_xlog_location()
> function to return that when recovery is in progress. It currently
> throws an error during hot standby.
>
Not sure. I don't really like to monitor functions that return
different things depending on a scenario.
Assume I monitor it, and then do a failover. Suddenly the values I
monitor mean something else.
I think I'd prefer a separate function to monitor this status on the
slave. Oh, and it'd be nice if that one worked in HS mode both when in
streaming and non-streaming mode :-)
--
Magnus Hagander
Me: http://www.hagander.net/
Work: http://www.redpill-linpro.com/
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