[pgpool-general: 6406] Re: Online Recovery vs WAL acrhiving

Andre Piwoni apiwoni at webmd.net
Tue Feb 12 04:57:59 JST 2019

How about follow master command when slave just needs to repoint to the new
I cannot tell you how many scripts for follow_master_command I have found
on the web that take base backup directly or via repmgr. In case of larger
database and several slaves this is just plain waste of resources.
In it's simplest terms follow_master_command shouldn't be nothing more than:
(1) Stop slave
(2) Repoint to new master
(3) Start slave (recover from WAL archive data written by master while
being down)

Is this accurate?

On Fri, Oct 19, 2018 at 7:01 PM Tatsuo Ishii <ishii at sraoss.co.jp> wrote:

> > It seems that online recovery scripts take base backup of the primary
> > to recover downed node.
> > With streaming replication and WAL archiving enabled downed node can
> > be recovered when it is started again much faster than taking entire
> > base backup of the primary.
> > So question comes to mind, what is the advantage of using
> > time-consuming online recovery over WAL archiving restore process?
> > Is attaching downed node to PgPool automatically the only benefit?
> If you are sure that the downed node can be recovered by fetching WAL
> from archive at its starting up, you don't need to use online recovery
> at all. You just start the standby and issue pcp_attach_node is
> enough (assuming that the standby node was once attached to
> Pgpool-II).
> On the other hand, if the downed node cannot be recovered due to its
> database corruption or some other problems, you have to copy primary
> database to standby, and that's what online recovery usually does.
> Another scenario is adding brand new standby. In this case you need
> fully copy primary database anyway and you should use on line
> recovery.
> Best regards,
> --
> Tatsuo Ishii
> SRA OSS, Inc. Japan
> English: http://www.sraoss.co.jp/index_en.php
> Japanese:http://www.sraoss.co.jp


*Andre Piwoni*

Sr. Software Developer, BI/Database

*Web*MD Health Services

Mobile: 801.541.4722

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