Message-ID: <49EE1E3F.9050307@enterprisedb.com>
Date: Tue, 21 Apr 2009 22:27:59 +0300
From: Heikki Linnakangas <heikki.linnakangas@enterprisedb.com>
Organization: EnterpriseDB
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To: Fujii Masao <masao.fujii@gmail.com>
CC: Simon Riggs <simon@2ndquadrant.com>,
	Guillaume Smet <guillaume.smet@gmail.com>,
	Tom Lane <tgl@sss.pgh.pa.us>, Peter Eisentraut <peter_e@gmx.net>,
	Kevin Grittner <Kevin.Grittner@wicourts.gov>,
	pgsql-hackers <pgsql-hackers@postgresql.org>
Subject: Re: New trigger option of pg_standby
References: <3f0b79eb0903242329j12865d55s348f5c873a956e71@mail.gmail.com>	
	<3f0b79eb0903311901h70520cc8u9c0f1d8f4193923b@mail.gmail.com>	
	<3f0b79eb0904022042g35b8e3cah9432ff764e721a3@mail.gmail.com>	
	<1d4e0c10904071456m735e3f67q123b87243d2f6f2a@mail.gmail.com>	
	<3f0b79eb0904071817u5c32254ei61f7e68e54669d9e@mail.gmail.com>	
	<49DDEE72.6030803@enterprisedb.com>	
	<3f0b79eb0904092047w355e0b3ar527a9285b161ef91@mail.gmail.com>	
	<1239381103.16396.30.camel@ebony.2ndQuadrant>	
	<3f0b79eb0904122252t1f4c5860v919d199f399ccf72@mail.gmail.com>	
	<3f0b79eb0904132241p18084914g792cb8e5ab3eebb3@mail.gmail.com>
	<3f0b79eb0904150101pb1c59a3ubb422867e8e6a944@mail.gmail.com>
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Fujii Masao wrote:
> Hi,
> 
> On Tue, Apr 14, 2009 at 2:41 PM, Fujii Masao <masao.fujii@gmail.com> wrote:
>> I'd like to propose another simple idea; pg_standby deletes the
>> trigger file *whenever* the nextWALfile is a timeline history file.
>> A timeline history file is restored at the end of recovery, so it's
>> guaranteed that the trigger file is deleted whether nextWALfile
>> exists or not.
>>
>> A timeline history file is restored also at the beginning of
>> recovery, so the accidentally remaining trigger file is deleted
>> in early warm-standby as a side-effect of this idea.
> 
> Here is the revised patch as above.
> 
> If you notice something, please feel free to comment.

Ok, looking at this in more detail now. A couple of small things:

We mustn't remove the trigger file immediately even in fast mode. As 
noted elsewhere in this thread, we have the same bug in fast mode where 
pg_standby gets stuck if you copy WAL files directly into pg_xlog.

pg_standby should exit with code 0 only if the file is restore 
successfully. As the patch stands it also returns 0 when smart failover 
is done.

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