Jan,

But as you said they all have to be in the same cluster, correct ?

Dave Cramer

On 9 October 2014 18:31, Jan Wieck <jan at wi3ck.info> wrote:

> On 10/09/2014 05:26 PM, Glyn Astill wrote:
> >> From: Granthana Biswas <granthana.biswas at gmail.com>
> >>To: Glyn Astill <glynastill at yahoo.co.uk>
> >>Sent: Thursday, 9 October 2014, 16:34
> >>Subject: Re: [Slony1-general] Error with Slony replication from another
> slony cluster slave
> >>
> >>
> >>
> >>Hi Glyn,
> >>
> >>
> >>In my case I have two clusters:
> >>
> >>
> >>Cluster1 ->  replicating from DB1 -> DB2
> >>Cluster2 ->  replicating from DB1 -> DB3
> >>
> >>
> >>Can I stop Cluster2 and add DB3 to Cluster1 with DB2 as its master? Or
> do I have to delete the data first in DB3?
> >>
> >>
> >
> > You'll want to run DROP NODE against each node in Cluster2, (or if on
> 2.0+ you can get away with just DROP SCHEMA _Cluster2 CASCADE) and stop the
> slons for Cluster2.
>
>
> Cascading, forwarding and all that is one of the core concepts of Slony.
> If you create one single setup looking like this:
>
>      DB1 -> DB2 -> DB3
>
> then you have a lot more flexibility and functionality than is obvious
> at first. Aside from being able to fail over to DB2.
>
> Slony will let you "MOVE" the master role from DB1 to DB2. That
> operation will not just make DB2 the master, but at the same time DB1
> becomes a replica that doesn't need an initial sync, so your setup now
> would look like this:
>
>      DB1 <- DB2 -> DB3
>
> This is useful if you need to perform some maintenance on DB1. At this
> point DB2 is your master an you would just stop the slon process for
> DB1, do whatever you need to do, and start the slon process again. Once
> DB1 has caught up, you just transfer the master role back and everything
> is as it was.
>
> What also works is that if you need to perform maintenance on DB2, it
> doesn't mean that DB3 has to fall behind too. You can easily change the
> data provider for DB3 to be DB1, so your configuration changes to
>
>      DB1 -> DB2
>       |
>       V
>      DB3
>
> At this point you stop the slon process for DB2, perform what you need
> to do on DB2, start the slon process and after DB2 has caught up, make
> it the data provider for DB3 again.
>
>
> Regards,
> Jan
>
> --
> Jan Wieck
> Senior Software Engineer
> http://slony.info
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>
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