Ian Barwick 9273e7af73 "standby switchover": avoid potential race condition with WAL location check ...

Immediately after the demotion candidate (primary) has shut down, we can't
be absolutely sure that the walreceiver has flushed all WAL to disk, so
checking pg_last_wal_receive_lsn() at that point might not reflect
the actual last available WAL location.

To handle this, we'll loop for a while (timeout controlled by configuration
parameter "wal_receive_check_timeout") before finally deciding whether
the standby is still behind the shut-down primary.

Addresses issue raised in GitHub #518.

2019-02-01 12:06:22 +09:00

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