On Fri, Mar 11, 2011 at 10:18 PM, Robert Haas <robertmhaas@gmail.com> wrote:
>> I added this replication timeout patch into next CF.
>>
>> I explain why this feature is required for the future review;
>>
>> Without this feature, walsender might unexpectedly remain for a while when
>> the standby crashes or the network outage happens. TCP keepalive can
>> improve this situation to a certain extent, but it's not perfect. Remaining
>> walsender can cause some problems.
>>
>> For example, when hot_standby_feedback is enabled, such a remaining
>> walsender would prevent oldest xmin from advancing and interfere with
>> vacuuming on the master. For example, when you use synchronous
>> replication and walsender in SYNC mode gets stuck, any synchronous
>> standby candidate cannot switch to SYNC mode until that walsender exits,
>> and all the transactions would pause.
>>
>> This feature causes walsender to exit when there is no reply from the
>> standby before the replication timeout expires. Then we can avoid the
>> above problems.
>
> I think we should consider making this change for 9.1. This is a real
> wart, and it's going to become even more of a problem with sync rep, I
> think.
Yeah, that's a welcome! Please feel free to review the patch.
Regards,
--
Fujii Masao
NIPPON TELEGRAPH AND TELEPHONE CORPORATION
NTT Open Source Software Center
