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To: Martin S <martins.listz@gmail.com>
Cc: pgsql-admin@postgresql.org
Subject: Re: Recover from failover
References: 
 <CAFTQ5y3epvSG8gnXdQVbvt_ybr4xsQh+CNU+xM1uZxpwf90WrQ@mail.gmail.com>
From: Jerry Sievers <gsievers19@comcast.net>
Date: Mon, 05 Dec 2011 21:41:31 -0500
In-Reply-To: 
 <CAFTQ5y3epvSG8gnXdQVbvt_ybr4xsQh+CNU+xM1uZxpwf90WrQ@mail.gmail.com>
	(Martin S.'s message of "Mon\, 5 Dec 2011 17\:22\:04 -0300")
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Martin S <martins.listz@gmail.com> writes:

> Hello list,
>
> May be this information is inside the documentation, but couldn't find it.
>
> I'm doing some tests with postgres 9.1.1 and replication, and I was
> wandering if there is some information about how to recover from a
> failover.
>
> Suppose I'm doing some kernel upgrades on the master, so in order to
> avoid downtime, I promote the slave to become the master, and reboot
> the old-master. Once the old-master is up and running again, I want it
> to be the master as it was before. The problem are the updates and
> inserts made while it was offline. Does it recovers automagically by
> streaming or something? Do you have any procedures/recommendations to
> do it?

About the only way you can role reverse master and standby is to stop
immediate the master, online the standby and then config the old
master as a standby and point it to the new master. 

Doing a normal stop on the original master before onlining the
standby, then making changes to the old master DB and you'll have to
refresh the old master from a base backup before putting it into
recovery.

Most admins will tell you to refresh the old master in either case to
be on the safe side.  This is the conventional and guaranteed to work
approach.

HTH

> Cheers,
>
> Martin
>
> -- 
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-- 
Jerry Sievers
Postgres DBA/Development Consulting
e: postgres.consulting@comcast.net
p: 305.321.1144