Simon Riggs wrote:
The essential choice is "What would you like the max failover time to be?". Some users want one server with max 5 mins behind, some want two servers, one with 0 seconds behind, one with 12 hours behind
It's not quite that simple. Setting max_standby_delay=5mins means that you're willing to wait 5 minutes for each query to die. Which means that in worst case you have to stop for 5 minutes at every single vacuum record, and fall behind much more than 5 minutes.
You could make it more like that by tracking the timestamps in commit records, and/or having some sort of a moving average logic in the timeout, where you allow more waiting if you haven't waited for a long time, and kill queries more aggressively if you've had to wait a lot recently.
It should also be noted that the control functions allow you to connect to the database and manually pause/resume the replay. So you can for example set max_standby_delay=0 during the day, but pause the replay manually before starting a nightly report.
-- Heikki Linnakangas EnterpriseDB http://www.enterprisedb.com -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
