Re: Mult-standby streaming replication master failover

On Tue, Feb 10, 2015 at 1:26 AM, Vladislav Tchernev <vtchernev(at)gmail(dot)com> wrote:
> I am trying to figure out a clear way to preform a post-disaster (where the
> master hasn't had the chance to shut down properly) master failover in a
> multi-standby streaming replication setup. I found a couple of old posts
> suggesting that the choice of the new master is very important and if not
> done correctly might lead to database corruption.The posts suggest that the
> first thing to do is to find the most caught-up replica, by compare WAL
> replay locations among all standby servers. This makes perfect scene but
> also makes the failover process a little bit more complicated and difficult
> to automate. I guess my question is, does my understanding is right and if
> there are any changes in this regard in the newer Postgresql 9.3/9.4
> releases.

You are right to take this approach. One of the modifications that 9.3
brought is that a standby is able to follow a timeline switch, so by
promoting the most-updated standby all the other existing standbys
will be able to follow it just by redirecting their primary_conninfo
flow to the newly-promoted node. For the old master, you may as well
rewind it with pg_rewind if WAL forked (assuming that page checksum is
enabled for 9.3~ or that wal_log_hints is enabled in 9.4~).
--
Michael