Re: Re: Hot Standby query cancellation and Streaming Replication integration

Josh Berkus <josh@agliodbs.com>

From: Josh Berkus <josh@agliodbs.com>
To: Greg Stark <gsstark@mit.edu>
Cc: Greg Smith <greg@2ndquadrant.com>, PostgreSQL-development <pgsql-hackers@postgresql.org>
Date: 2010-03-01T19:21:48Z
Lists: pgsql-hackers
> So I think the primary solution currently is to raise max_standby_age.
> 
> However there is a concern with max_standby_age. If you set it to,
> say, 300s. Then run a 300s query on the slave which causes the slave
> to fall 299s behind. Now you start a new query on the slave -- it gets
> a snapshot based on the point in time that the slave is currently at.
> If it hits a conflict it will only have 1s to finish before the
> conflict causes the query to be cancelled.

Completely aside from that, how many users are going to be happy with a
slave server which is constantly 5 minutes behind?

--Josh Berkus