Hi Andrew,

If I understand the slony replication correct, is that after I do switchover
or failover what it can do is promote another node to replace its origin
node. If lets say failover, after origin node failed and another node
replaced it, all other slave nodes in group will seek for sets from new
master, basically failover script will change the "provider" from subscribe
set command to the new master node. Therefore, new master should first sync
with old master with all the data and having all sets isn't it? 

Let's say Old master(node 1) has five tables (table 1,2,3,4,5) and new
master (node 2) has only (table 1 and 2). After switch over or failover to
the new master (node 2), will node 2 sync with old master and has all 5
tables? 

What if I do switch back to Node 1 from Node 2, now will both node 1 and 2
has all 5 tables on itself? 

This really needs to get clear first. Has someone tested this and know how
it works?


Andrew Sullivan-8 wrote:
> 
> No, I don't believe this is right, assuming I understand you.
> Switchover works on sets, so you will effectively make node 2 the
> origin for sets 1 and 2, but sets 3-5 will remain origined on node 1.
> 
> The key thing here to get is that Slony has no real notion of "all
> nodes" involved in replication from one node to another.  It's just
> not interested in that.  At the basic level, it is set-oriented.  So
> the sets are nodes involved in replicating that set.  You can (could?)
> conveniently work on supersets using external tools, but Slony doesn't
> itself care about that.
> 
> You raise an interesting point about the documentation, however, which
> is that it doesn't make clear that the new origin (in the case of MOVE
> SET) has to be actually subscribed before moving to it.  This is
> similarly unclear in the FAILOVER command, although I suppose in that
> case it ought to be obvious that if you're not already subscribed,
> failing over to such a node is doomed.
> 
> A
> -- 
> Andrew Sullivan
> ajs at crankycanuck.ca
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> Slony1-general mailing list
> Slony1-general at lists.slony.info
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> 
> 

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