[pgpool-general: 6695] Re: Query
Lakshmi Raghavendra
lakshmiym108 at gmail.com
Mon Sep 2 13:31:03 JST 2019
Hi Tatsuo,
Please find attached the zip file.
Thanks And Regards,
Lakshmi Y M
On Mon, Sep 2, 2019 at 5:13 AM Tatsuo Ishii <ishii at sraoss.co.jp> wrote:
> Hi Lakshmi,
>
> Your attached files are too large to accept by the mailing list. Can
> you compress them and post the message along the compressed attached
> files?
>
> Best regards,
> --
> Tatsuo Ishii
> SRA OSS, Inc. Japan
> English: http://www.sraoss.co.jp/index_en.php
> Japanese:http://www.sraoss.co.jp
>
> From: Lakshmi Raghavendra <lakshmiym108 at gmail.com>
> Subject: Fwd: [pgpool-general: 6672] Query
> Date: Sun, 1 Sep 2019 23:14:30 +0530
> Message-ID: <
> CAHHVJ5sRoVFEEW4EoZLgudCTTm0cqGjXhbbkpnOiimcs4euUSw at mail.gmail.com>
>
> > ---------- Forwarded message ---------
> > From: Lakshmi Raghavendra <lakshmiym108 at gmail.com>
> > Date: Sat, Aug 31, 2019 at 10:17 PM
> > Subject: Re: [pgpool-general: 6672] Query
> > To: Tatsuo Ishii <ishii at sraoss.co.jp>
> > Cc: Muhammad Usama <m.usama at gmail.com>, <pgpool-general at pgpool.net>
> >
> >
> > Hi Usama / Tatsuo,
> >
> > Received the email notification today, sorry for the delayed
> > response.
> > Please find attached the pgpool-II log for the same.
> >
> > So basically below is the short summary of the issue:
> >
> >
> > Node -1 : Pgpool Master + Postgres Master
> >
> > Node -2 : Pgpool Standby + Postgres Standby
> >
> > Node-3 : Pgpool Standby + Postgres Standby
> >
> >
> > When network failure happens and Node-1 goes out of network, below is the
> > status :
> >
> > Node-1 : Pgpool Lost status + Postgres Standby (down)
> >
> > Node -2 : Pgpool Master + Postgres Master
> >
> > Node-3 : Pgpool Standby + Postgres Standby
> >
> >
> > Now when Node-1 comes back to network , below is the status causing the
> > pgpool cluster to get into imbalance :
> >
> >
> >
> > lcm-34-189:~ # psql -h 10.198.34.191 -p 9999 -U pgpool postgres -c "show
> > pool_nodes"
> > Password for user pgpool:
> > node_id | hostname | port | status | lb_weight | role |
> select_cnt
> > | load_balance_node | replication_delay | last_status_change
> >
> ---------+---------------+------+--------+-----------+---------+------------+-------------------+-------------------+---------------------
> > 0 | 10.198.34.188 | 5432 | up | 0.333333 | primary | 0
> > | true | 0 | 2019-08-31 16:40:26
> > 1 | 10.198.34.189 | 5432 | up | 0.333333 | standby | 0
> > | false | 1013552 | 2019-08-31 16:40:26
> > 2 | 10.198.34.190 | 5432 | up | 0.333333 | standby | 0
> > | false | 0 | 2019-08-31 16:40:26
> > (3 rows)
> >
> > lcm-34-189:~ # /usr/local/bin/pcp_watchdog_info -p 9898 -h 10.198.34.191
> -U
> > pgpool
> > Password:
> > 3 NO lcm-34-188.dev.lcm.local:9999 Linux lcm-34-188.dev.lcm.local
> > 10.198.34.188
> >
> > lcm-34-189.dev.lcm.local:9999 Linux lcm-34-189.dev.lcm.local
> > lcm-34-189.dev.lcm.local 9999 9000 7 STANDBY
> > lcm-34-188.dev.lcm.local:9999 Linux lcm-34-188.dev.lcm.local
> 10.198.34.188
> > 9999 9000 4 MASTER
> > lcm-34-190.dev.lcm.local:9999 Linux lcm-34-190.dev.lcm.local
> 10.198.34.190
> > 9999 9000 4 MASTER
> > lcm-34-189:~ #
> >
> >
> >
> > Thanks And Regards,
> >
> > Lakshmi Y M
> >
> > On Tue, Aug 20, 2019 at 8:55 AM Tatsuo Ishii <ishii at sraoss.co.jp> wrote:
> >
> >> > On Sat, Aug 17, 2019 at 12:28 PM Tatsuo Ishii <ishii at sraoss.co.jp>
> >> wrote:
> >> >
> >> >> > Hi Pgpool Team,
> >> >> >
> >> >> > *We are nearing a production release and running into
> >> the
> >> >> > below issues.*
> >> >> > Replies at the earliest would be highly helpful and greatly
> >> appreciated.
> >> >> > Please let us know on how to get rid of the below issues.
> >> >> >
> >> >> > We have a 3 node pgpool + postgres cluster - M1 , M2, M3. The
> >> pgpool.conf
> >> >> > is as attached.
> >> >> >
> >> >> > *Case I : *
> >> >> > M1 - Pgpool Master + Postgres Master
> >> >> > M2 , M3 - Pgpool slave + Postgres slave
> >> >> >
> >> >> > - M1 goes out of network. its marked as LOST in the pgpool cluster
> >> >> > - M2 becomes postgres master
> >> >> > - M3 becomes pgpool master.
> >> >> > - When M1 comes back to the network, pgpool is able to solve split
> >> brain.
> >> >> > However, its changing the postgres master back to M1 by logging a
> >> >> statement
> >> >> > - "LOG: primary node was chenged after the sync from new master",
> so
> >> >> since
> >> >> > M2 was already postgres master (and its trigger file is not
> touched)
> >> its
> >> >> > not able to sync to the new master.
> >> >> > *I somehow want to avoid this postgres master change..please let us
> >> know
> >> >> if
> >> >> > there is a way to avoid it*
> >> >>
> >> >> Sorry but I don't know how to prevent this. Probably when former
> >> >> watchdog master recovers from an network outage and there's already
> >> >> PostgreSQL primary server, the watchdog master should not sync the
> >> >> state. What do you think Usama?
> >> >>
> >> >
> >> > Yes, that's true, there is no functionality that exists in Pgpool-II
> to
> >> > disable the backend node status synch. In fact that
> >> > would be hazardous if we somehow disable the node status syncing.
> >> >
> >> > But having said that, In the mentioned scenario when the M1 comes back
> >> and
> >> > join the watchdog cluster Pgpool-II should have
> >> > kept the M2 as the true master while resolving the split-brain. The
> >> > algorithm used to resolve the true master considers quite a
> >> > few parameters and for the scenario, you explained, M2 should have
> kept
> >> the
> >> > master node status while M1 should have resigned
> >> > after joining back the cluster and effectively the M1 node should have
> >> been
> >> > syncing the status from M2 ( keeping the proper primary node)
> >> > not the other way around.
> >> > Can you please share the Pgpool-II log files so that I can have a
> look at
> >> > what went wrong in this case.
> >>
> >> Usama,
> >>
> >> Ok, the scenario (PostgreSQL primary x 2 in the end) should have not
> >> happend. That's a good news.
> >>
> >> Lakshmi,
> >>
> >> Can you please provide the Pgpool-II log files as Usama requested?
> >>
> >> Best regards,
> >> --
> >> Tatsuo Ishii
> >> SRA OSS, Inc. Japan
> >> English: http://www.sraoss.co.jp/index_en.php
> >> Japanese:http://www.sraoss.co.jp
> >>
>
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