On 2016/08/31 9:40, Josh Berkus wrote:
> On 08/30/2016 05:35 PM, Michael Paquier wrote:
>> Assuming that all servers are connected at the moment decision is
>> made, you need to wait for s1, s2 *and* s3 to acknowledge depending on
>> synchronous_commit. By default that would be waiting for the LSN to
>> have been flushed on all of them. And the important point to get is
>> that what has been committed is dependent on the order of the items
>> listed. This is not quorum commit, in which case having only
>> confirmation from 3 servers in the set of 5 servers listed would be
>> fine.
>>
>> If for example s2 and s4 are not connected at the moment of the
>> decision, you'd need to wait for acknowledgment from s1, s3 and s5
>> before moving on.
>
> OK, so this says to me that we need a bunch of additional documentation
> on this feature, because the existing docs read like it's "any 3 out of
> the list" instead of "the first 3 which are connected".
IIUC, "any 3 out of the list" will be the quorum logic. Currently, the
order of listing of standby names determines their priority of being the
next potential synchronous standby if and when we start running short of
3. So "the first 3 which are connected" is exactly the feature that's
available. Of course unless I am missing something.
Thanks,
Amit