Today I encountered an interesting situation.
1) A streaming replication primary server and a standby server is running. At this point max_connections = 100 on both
servers.
2) Shutdown both servers.
3) Change max_connections to 1100 on both servers and restart both servers.
4) The primary server happily started but the standby server won't because of lacking resource.
5) Shutdown both servers.
6) Restore max_connections to 100 on both servers and restart both servers.
7) The primary server happily started but the standby server won't because of the reason below.
32695 2015-08-11 13:46:22 JST FATAL: hot standby is not possible because max_connections = 100 is a lower setting than
onthe master server (its value was 1100)
32695 2015-08-11 13:46:22 JST CONTEXT: xlog redo parameter change: max_connections=1100 max_worker_processes=8
max_prepared_xacts=10max_locks_per_xact=64 wal_level=hot_standby wal_log_hints=off
32693 2015-08-11 13:46:22 JST LOG: startup process (PID 32695) exited with exit code 1
32693 2015-08-11 13:46:22 JST LOG: terminating any other active server processes
I think this is because pg_control on the standby remembers that the
previous primary server's max_connections = 1100 even if the standby
server fails to start. Shouldn't we update pg_control file only when
standby succeeds to start?
Best regards,
--
Tatsuo Ishii
SRA OSS, Inc. Japan
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