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Re: New trigger file in pg_standby to promote the standby to the primary

From: "Fujii Masao" <masao(dot)fujii(at)gmail(dot)com>
To: "Simon Riggs" <simon(at)2ndquadrant(dot)com>
Cc: pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: New trigger file in pg_standby to promote the standby to the primary
Date: 2008-11-28 03:43:40
Message-ID: 3f0b79eb0811271943l7caaebc1t54efc7c040e02a61@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-hackers
Hello, Simon.

On Fri, Nov 28, 2008 at 4:29 AM, Simon Riggs <simon(at)2ndquadrant(dot)com> wrote:
>
> On Wed, 2008-11-26 at 00:03 +0900, Fujii Masao wrote:
>
>> In current pg_standby, the presence of the trigger file causes
>> recovery to end whether or not the next WAL file is available.
>> Thereby, some transactions in the available WAL files will be
>> lost. So, we cannot use this trigger file to promote the standby
>> to the primary.
>>
>> I'd like to add new trigger file option into pg_standby, and end
>> recovery after redoing all the available WAL files. Concretely
>> speaking, I would always make pg_standby look for the trigger
>> file after trying to restore the WAL file once. If the trigger file
>> is present, pg_standby exits immediately without deleting the
>> trigger file. Subsequent pg_standby uses the existing trigger
>> file.
>>
>> This option is also useful for warm-standby.
>>
>> Any comments welcome!
>
> Yes, it was on my todo. Happy for you to do it if you have time.
>
> Sometimes we want fast failover, sometimes we want complete catchup. So
> my solution is to put a message in the trigger file to say which one we
> want.
>
> Happy for the default to change to "complete catchup".

I have added the new trigger option into pg_standby in the latest patch,
before reading your comment. But I think that your idea is more flexible,
so I will change it by the next patch.

Regards,

-- 
Fujii Masao
NIPPON TELEGRAPH AND TELEPHONE CORPORATION
NTT Open Source Software Center

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