Message-ID: <4A0C6B71.4050003@enterprisedb.com>
Date: Thu, 14 May 2009 22:05:21 +0300
From: Heikki Linnakangas <heikki.linnakangas@enterprisedb.com>
Organization: EnterpriseDB
User-Agent: Mozilla-Thunderbird 2.0.0.19 (X11/20090103)
MIME-Version: 1.0
To: Fujii Masao <masao.fujii@gmail.com>
CC: Simon Riggs <simon@2ndquadrant.com>, Tom Lane <tgl@sss.pgh.pa.us>,
	Guillaume Smet <guillaume.smet@gmail.com>,
	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>	
	<49F01D79.8020805@enterprisedb.com>	
	<3f0b79eb0904230515p751b5248n6ef96880617db055@mail.gmail.com>	
	<4A095A39.3030100@enterprisedb.com>	
	<3f0b79eb0905130127u3a3275b1w79f4d8cb729ded36@mail.gmail.com>	
	<4A0A86D2.9080602@enterprisedb.com>
	<1985.1242234105@sss.pgh.pa.us>	
	<4A0B10C7.2040309@enterprisedb.com>	
	<1242247404.3843.503.camel@ebony.2ndQuadrant>	
	<1242315415.3843.526.camel@ebony.2ndQuadrant>
	<3f0b79eb0905141149lf5cef92j538f490c86dfedf8@mail.gmail.com>
In-Reply-To: <3f0b79eb0905141149lf5cef92j538f490c86dfedf8@mail.gmail.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 7bit

Fujii Masao wrote:
> On Fri, May 15, 2009 at 12:36 AM, Simon Riggs <simon@2ndquadrant.com> wrote:
>> On Wed, 2009-05-13 at 21:43 +0100, Simon Riggs wrote:
>>> On Wed, 2009-05-13 at 21:26 +0300, Heikki Linnakangas wrote:
>>>
>>>> This whole thing can be considered to be a new feature.
>>> recovery.conf will contain a new optional parameter:
>>>
>>> recovery_end_command (string)
>> Implemented.
> 
>> + 		ereport(signaled ? FATAL : WARNING,
>> + 				(errmsg("recovery_end_command \"%s\": return code %d",
>> + 								xlogRecoveryEndCmd, rc)));
> 
> In fast failover case, pg_standby has to delete the trigger file immediately
> if it's found. Otherwise, recovery may go wrong as I already described.
> http://archives.postgresql.org/pgsql-hackers/2009-04/msg01139.php

And if you delete it immediately, you risk getting stuck if there's 
extra WAL files in pg_xlog. So still need the change in the backend to 
not call restore_command again for a WAL segment equal to or later than 
one that it already failed to restore. Or, we can truncate the trigger 
file to make it behave like a smart failover for the subsequent 
pg_standby calls.

> So, in fast mode, recovery_end_command would always fail to delete the
> trigger file, and cause warning. This is odd behavior, I think. We should
> change WARNING to DEBUG2 like RestoreArchivedFile() in the above code?

I think we should just change the pg_standby example to use "rm -f" 
rather than "rm". It seems useful to give a warning if the command fails.

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