Re: Synchronous replication

On 14/07/10 09:50, Fujii Masao wrote:
> Quorum commit
> -------------
> In previous discussion about synchronous replication, some people
> wanted the quorum commit feature. This feature is included in also
> Zontan's synchronous replication patch, so I decided to create it.
>
> The patch provides quorum parameter in postgresql.conf, which
> specifies how many standby servers transaction commit will wait for
> WAL records to be replicated to, before the command returns a
> "success" indication to the client. The default value is zero, which
> always doesn't make transaction commit wait for replication without
> regard to replication_mode. Also transaction commit always doesn't
> wait for replication to asynchronous standby (i.e., replication_mode
> is set to async) without regard to this parameter. If quorum is more
> than the number of synchronous standbys, transaction commit returns
> a "success" when the ACK has arrived from all of synchronous standbys.

There should be a way to specify "wait for *all* connected standby
servers to acknowledge"

> Protocol
> --------
> I extended the handshake message "START_REPLICATION" so that it
> includes replication_mode read from recovery.conf. If 'async' is
> passed, the master thinks that it doesn't need to wait for the ACK
> from the standby.

Please use self-explanatory names for the modes in START_REPLICATION
command, instead of just an integer.

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