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I have a streaming replication setup using postgresql 9.3. I have two servers, the master (server_1) and the slave (server_2).

The other day I did a failover to my slave (server_2). Now server_2 has been running as master for a couple of days, and I have now setup my primary master (server_1) again, and it now runs as master. I would like to avoid reinstalling server_2 before turning it into a slave of server_1 again. How can I do that? What dir's should I delete etc, in order to have a "clean" server that I can use as slave again?

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The only officially supported method is to make a new base backup, or:

  • pg_start_backup() on the new master
  • rsync from new master to old master
  • pg_stop_backup()
  • ensure WAL got copied over and applied
  • create recovery.conf
  • start resynced server

The 3rd party tool pg_rewind is intended for that purpose. I haven't worked with it as yet and can't vouch for it in production.

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  • Sure, but don't I have to "delete" the old cluster from the to-be-slave, before I start doing the above?
    – Niels Kristian
    Apr 2, 2014 at 10:31
  • @NielsKristian If you use pg_basebackup, yes. If you use rsync, no, because rsync can incrementally update it.
    – Craig Ringer
    Apr 3, 2014 at 1:14
  • I see, that was actually the answer I was looking for! Thank you Craig, you are one of the most helpful persons I can think of :-)
    – Niels Kristian
    Apr 3, 2014 at 8:18

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