On Sun, Aug 11, 2013 at 5:51 AM, ascot(dot)moss(at)gmail(dot)com
<ascot(dot)moss(at)gmail(dot)com> wrote:
> Hi,
>
> I have a pair of PG servers, a master and a replica, all read-write queries are handled by the master, read-only ones are by the replica.
>
> From time to time the replica itself is too busy, all read-only queries will get inconsistent results because of replication lag, sometimes it can be longer than 6 minutes. I am thinking to add multiple replicas to off-load read-only queries, can you please suggest a way to monitor and failover the read-only query when the replication lag in a replica is more than 5 minutes?
I assume that you could use pgpool for that. It has some monitoring
features for replication delay and it can do read-only load balancing
among several servers. You also shouldn't need to change your
application.
Have a look at its documentation to make an opinion:
http://pgpool.projects.pgfoundry.org/pgpool-II/doc/pgpool-en.html
Regards,
--
Michael