On 11/20/2016 10:00 PM, Subhankar Chattopadhyay wrote:
Thanks for reply. In situations where slave is behind master, if I don't start over, will it catch up automatically? I am using 9.4 version.
it should stay within a few seconds under normal conditions. why is it falling behind, is your write workload too high for the speed of the connection between the hosts? or is the slave shut down for some period of time?
If the slave is intermittently offline, and if you're using replication slots (that was a new feature in 9.4), then the master will hold a queue of pending data as long as is needed until the slave catches up again.
Alternately, you can increase wal_keep_segments for a long enough interval to cover the worst case time the slave is offline, or you can implement a wal archive that the slave can recover from when resuming streaming replication.
See https://www.postgresql.org/docs/9.4/static/warm-standby.html for discussions of these various options.
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