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
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