Hi, Yes, definitely I am hanging out here. If you have more specific questions to Pgpool-II, you are encouraged to be subscribed to the Pgpool-II mailing list. https://www.pgpool.net/mailman/listinfo/pgpool-general Best regards, -- Tatsuo Ishii SRA OSS, Inc. Japan English: http://www.sraoss.co.jp/index_en.php Japanese:http://www.sraoss.co.jp > What he said, and you also may want to look at pgpool-II. I’ve had fairly good luck with that and Tatsuo (the author) hangs out here occasionally too. > ― > Jay > > Sent from my iPad > >> On Jan 5, 2018, at 4:00 PM, Jehan-Guillaume (ioguix) de Rorthais <ioguix@xxxxxxx> wrote: >> >> On Fri, 5 Jan 2018 13:07:10 -0600 >> Azimuddin Mohammed <azimeiu@xxxxxxxxx> wrote: >> >>> Hello, >>> I am little confused with how HA works in postgres. Reading the article >>> which state as below "*If the primary server fails and the standby server >>> becomes the new primary, and then the old primary restarts, you must have a >>> mechanism for informing the old primary that it is no longer the primary. >>> This is sometimes known as STONITH (Shoot The Other Node In The Head), >>> which is necessary to avoid situations where both systems think they are >>> the primary, which will lead to confusion and ultimately data loss.* >>> >>> *Many failover systems use just two systems, the primary and the standby, >>> connected by some kind of heartbeat mechanism to continually verify the >>> connectivity between the two and the viability of the primary. It is also >>> possible to use a third system (called a witness server) to prevent some >>> cases of inappropriate failover, but the additional complexity might not be >>> worthwhile unless it is set up with sufficient care and rigorous testing.* >>> *PostgreSQL does not provide the system software required to identify a >>> failure on the primary and notify the standby database server. Many such >>> tools exist and are well integrated with the operating system facilities >>> required for successful failover, such as IP address migration."* >>> >>> Can someone explain how the HA failback will take place >> >> The failback need either to rebuild the old master as a standby (rsync, >> pg_basebackup, restore PITR, ...) or to use pg_rewind to rewind the old master >> to a point where it can catch up with the new master. >> >> Some tools tries to automate failback using pg_rewind (patroni, repmgr), but I >> have no experience with them. >> >>> and what open source tools we can use to make sure once the primary server >>> which failed over to slave will mark itself as slave. >> >> There's a lot of open source tools to build some HA around PgSQL: Repmgr, >> Patroni (based on etcd or zookeeper), PAF (based on Pacemaker), etc. You will >> have to spend a lot of time to make extensive tests, understand them, pick one >> and document your cluster. >> >> Regards, >> >
