[pgpool-general: 7637] Re: Pgpool replication delay
valsarajpv at gmail.com
Thu Jul 8 19:28:01 JST 2021
On Thu, Jul 8, 2021 at 3:35 PM Tatsuo Ishii <ishii at sraoss.co.jp> wrote:
> > Hi,
> > Set delay_threshold = 30 and load tested. The error is not seen.
> It seems Pgpool-II is avoiding the PostgreSQL backend having too much
> replication delay. Good.
> > The following appearing in log sometimes:
> > 2021-07-08 04:05:13: pid 4285: LOG: selecting backend connection
> > 2021-07-08 04:05:13: pid 4285: DETAIL: failover or failback event
> > detected, discarding existing connections
> This is normal. Pgpool detects there has been a failover/failback
> event. This means that existing connections (connection pools) to
> backend may not be usable any more. Thus pgpool creats new connections
> to backend.
> > Any thoughts on this?
> > Thanks!
> > On Sat, Jul 3, 2021 at 6:22 AM Tatsuo Ishii <ishii at sraoss.co.jp> wrote:
> >> >>> Any recommendations for this kind of scenario?
> >> >>
> >> >> synchronous_commit = remote_apply will help at the expense of
> >> >> performance.
> >> >
> >> > Another option is, setting delay_threshold of pgpool.conf to lower
> >> > value. Default is 10000000 which allows large replication delay. So
> >> > you might want to set smaller value for it.
> >> >
> >> > Note that observation of replication delay is done periodically,
> >> > defined by sr_check_period. This means that if replication delay grows
> >> > rapidly, the replication delay observed by pgpool could be outdated
> >> > and pgpool may send SELECT to delayed standby, and you might see the
> >> > error.
> >> >
> >> > In summary delay_threshold is not perfect but can be useful if you
> >> > want to keep on using asynchronous replication.
> >> Actually Pgpool-II has many other options that might help you. Please
> >> checkout the manual:
> >> Best regards,
> >> --
> >> Tatsuo Ishii
> >> SRA OSS, Inc. Japan
> >> English: http://www.sraoss.co.jp/index_en.php
> >> Japanese:http://www.sraoss.co.jp
> > --
> > Life is like this: "Just when we get all the answers of life.... God
> > changes the question paper....
> > Valsaraj Viswanathan
Life is like this: "Just when we get all the answers of life.... God
changes the question paper....
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