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ihippik / wal-listener

PostgreSQL WAL listener
Apache License 2.0
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Fix LSN not correctly updated #43

Closed StephenSorriaux closed 1 month ago

StephenSorriaux commented 2 months ago

Before this change, the LSN indicated in the server heartbeat was not used to in the status reply, leading to the logical replication being delayed at least by 1 change. The issue did not have an impact on the data being received from the replication but it was an issue when trying to stop the PostgreSQL server, as it will wait for the replication to be up to date before shutting down.

In my case, it prevented the PostgreSQL server to shut down completely, which is not great in a HA fashion.

The issue can be easily reproduced by starting this project and noticing on PostgreSQL using select * from pg_stat_replication; that the sent_lsn and write_lsn differs. Also trying to shut down using pg_ctl will lead to a pg_ctl: server does not shut down unless wal-listener is stopped in between.

This commits is inspired by what is done in the pglogrepl project (which is the "replication" part of pgx), in the logical replication example : https://github.com/jackc/pglogrepl/blob/master/example/pglogrepl_demo/main.go#L128

ihippik commented 1 month ago

Thank you @StephenSorriaux , i will check soon!