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Re: Synchronous replication

Dimitri Fontaine <dfontaine@hi-media.com>

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From: Dimitri Fontaine <dfontaine@hi-media.com>
To: Heikki Linnakangas <heikki.linnakangas@enterprisedb.com>
Cc: Fujii Masao <masao.fujii@gmail.com>, Robert Haas <robertmhaas@gmail.com>, PostgreSQL-development <pgsql-hackers@postgresql.org>
Date: 2010-07-16T17:26:27Z
Lists: pgsql-hackers 
Le 16 juil. 2010 à 12:43, Heikki Linnakangas <heikki.linnakangas@enterprisedb.com> a écrit :

> On 16/07/10 10:40, Fujii Masao wrote:
>> So we should always prevent the standby from applying any WAL in pg_xlog
>> unless walreceiver is in progress. That is, if there is no WAL available
>> in the archive, the standby ignores pg_xlog and starts walreceiver
>> process to request for WAL streaming.
> 
> That completely defeats the purpose of storing streamed WAL in pg_xlog in the first place. The reason it's written and fsync'd to pg_xlog is that if the standby subsequently crashes, you can use the WAL from pg_xlog to reapply the WAL up to minRecoveryPoint. Otherwise you can't start up the standby anymore.

I guess we know for sure that this point has been fsync()ed on the Master, or that we could arrange it so that we know that?