Re: Synchronous replication

Fujii Masao wrote:
>> Intuitively by looking at the enumeration of replication_mode I'd think that
>> the sync standbys are all standby's that operate in a not async mode. That
>> would be clearer with a boolean sync (or not) and for sync standbys the
>> replication_mode specified.
>>
>
> You mean that something like synchronous_replication as the recovery.conf
> parameter should be added in addition to replication_mode? Since increasing
> the number of similar parameters would confuse users, I don't like do that.
>
I think what would be confusing if there is a mismatch between
implemented concepts and parameters.

1 does the master wait for standby servers on commit?
2 how many acknowledgements must the master receive before it can continue?
3 is a standby server a synchronous one, i.e. does it acknowledge a commit?
4 when do standby servers acknowledge a commit?
5 does it only wait when the standby's are connected, or also when they
are not connected?
6..?

When trying to match parameter names for the concepts above:
1 - does not exist, but can be answered with quorum_standbys = 0
2 - quorum_standbys
3 - yes, if replication_mode != async (here is were I thought I had to
think to much)
4 - replication modes recv, fsync and replay bot not async
5 - Zoltan's strict_sync_replication parameter

Just an idea, what about
for 4: acknowledge_commit = {no|recv|fsync|replay}
then 3 = yes, if acknowledge_commit != no

regards,
Yeb Havinga