On Wed, 05 Apr 2023 16:50:15 +0900 (JST) Tatsuo Ishii <ishii@xxxxxxxxxxxx> 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.
