Re: New trigger option of pg_standby

From: Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>
To: Fujii Masao <masao(dot)fujii(at)gmail(dot)com>
Cc: guillaume(dot)smet(at)gmail(dot)com, Kevin Grittner <Kevin(dot)Grittner(at)wicourts(dot)gov>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: New trigger option of pg_standby
Date: 2009-03-26 06:20:58
Message-ID: 49CB1ECA.5030507@enterprisedb.com
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Fujii Masao wrote:
> On Thu, Mar 26, 2009 at 12:48 AM, Guillaume Smet
> <guillaume(dot)smet(at)gmail(dot)com> wrote:
>> On Wed, Mar 25, 2009 at 2:59 PM, Kevin Grittner
>> <Kevin(dot)Grittner(at)wicourts(dot)gov> wrote:
>>> I find it hard to imagine a use case for the existing default
>>> behavior.
>> I thought a bit about it and I think it can be useful when your
>> priority is the availability of the service and you don't consider a
>> data loss that important: even if you have a lot of WALs segments to
>> replay, you may want to have your service up immediately in case of a
>> major problem.
>
> Yes, I also think that this is likely use case.
>
>> Keeping it is a good idea IMHO but I don't think it should be the default.
>
> What does "the default" mean? You mean that new trigger should use
> the existing trigger option character (-t)?

The existing behavior doesn't seem very useful to me either. Assuming
there is a use case though, we probably need to support both at the same
time, perhaps using different trigger files. If there's a use case for
both, conceivably someone will want to sometimes trigger the failover
immediately and sometimes after all WAL segments have been replayed.

Whatever we do, the signaling method to trigger failover should behave
the same.

--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com

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