From: | Fujii Masao <masao(dot)fujii(at)gmail(dot)com> |
---|---|
To: | Robert Haas <robertmhaas(at)gmail(dot)com> |
Cc: | Josh Berkus <josh(at)agliodbs(dot)com>, pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: Replication server timeout patch |
Date: | 2011-03-11 13:29:44 |
Message-ID: | AANLkTinxqXztx0mDmMGCUyDA1bduAzo76vLPzs7mpwZk@mail.gmail.com |
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Lists: | pgsql-hackers |
On Fri, Mar 11, 2011 at 10:18 PM, Robert Haas <robertmhaas(at)gmail(dot)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
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