Subject: Re: Re: [COMMITTERS] pgsql: Make standby server
	continuously retry 	restoring the next WAL
From: Simon Riggs <simon@2ndQuadrant.com>
To: Dimitri Fontaine <dfontaine@hi-media.com>
Cc: Heikki Linnakangas <heikki.linnakangas@enterprisedb.com>,
	Fujii Masao <masao.fujii@gmail.com>,
	PostgreSQL-development <pgsql-hackers@postgresql.org>
In-Reply-To: <877hqjc2kk.fsf@hi-media-techno.com>
References: <20100127152751.3B2047541B9@cvs.postgresql.org>
	<3f0b79eb1002092105r21e009d3v468496058ba04392@mail.gmail.com>
	<4B726120.80007@enterprisedb.com> <1265884657.7341.1192.camel@ebony>
	<4B73F678.8070109@enterprisedb.com> <1265891248.7341.1346.camel@ebony>
	<4B73FB99.4080403@enterprisedb.com> <1265893599.7341.1454.camel@ebony>
	<877hqjc2kk.fsf@hi-media-techno.com>
Content-Type: text/plain
Date: Thu, 11 Feb 2010 13:50:50 +0000
Message-Id: <1265896250.7341.1627.camel@ebony>
Mime-Version: 1.0
Content-Transfer-Encoding: 7bit

On Thu, 2010-02-11 at 14:41 +0100, Dimitri Fontaine wrote:
> Simon Riggs <simon@2ndQuadrant.com> writes:
> > If you were running pg_standby as the restore_command then this error
> > wouldn't happen. So you need to explain why running pg_standby cannot
> > solve your problem and why we must fix it by replicating code that has
> > previously existed elsewhere.
> 
> Let me try.
> 
> pg_standby will not let the server get back to streaming replication
> mode once it's done with driving the replay of all the WAL files
> available in the archive, but will have the server sits there waiting
> for the next file.
> 
> The way we want that is implemented now is to have the server switch
> back and forth between replaying from the archive and streaming from the
> master. So we want the server to restore from the archive the same way
> pg_standby used to, except that if the archive does not contain the next
> WAL files, we want to get back to streaming.
> 
> And the archive reading will resume at next network glitch.
> 
> I think it's the reasonning, I hope it explains what you see happening.

OK, thanks.

One question then: how do we ensure that the archive does not grow too
big? pg_standby cleans down the archive using %R. That function appears
to not exist anymore. 

-- 
 Simon Riggs           www.2ndQuadrant.com