From: | Jehan-Guillaume de Rorthais <jgdr(at)dalibo(dot)com> |
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To: | Tatsuo Ishii <ishii(at)sraoss(dot)co(dot)jp> |
Cc: | inzamam(dot)shafiq(at)hotmail(dot)com, cyberdemn(at)gmail(dot)com, pgsql-general(at)lists(dot)postgresql(dot)org |
Subject: | Re: Patroni vs pgpool II |
Date: | 2023-04-06 15:41:58 |
Message-ID: | 20230406174158.62c47a30@karst |
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Lists: | pgsql-general |
On Wed, 05 Apr 2023 16:50:15 +0900 (JST)
Tatsuo Ishii <ishii(at)sraoss(dot)co(dot)jp> wrote:
> > But, I heard PgPool is still affected by Split brain syndrome.
>
> Can you elaborate more? If more than 3 pgpool watchdog nodes (the
> number of nodes must be odd) are configured, a split brain can be
> avoided.
Split brain is a hard situation to avoid. I suppose OP is talking about
PostgreSQL split brain situation. I'm not sure how PgPool's watchdog would
avoid that.
To avoid split brain, you need to implement a combinaison of quorum and
(self-)fencing.
Patroni quorum is in the DCS's hands. Patroni's self-fencing can be achieved
with the (hardware) watchdog. You can also implement node fencing through the
"pre_promote" script to fence the old primary node before promoting the new one.
If you need HA with a high level of anti-split-brain security, you'll not be
able to avoid some sort of fencing, no matter what.
Good luck.
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