From: "Jan Wieck" <JanWieck at Yahoo.com>

>I think you realize by now that this is a functionality that falls into the 
>category of network monitoring.

Well, yes and no, Jan.

One of the features of Slony that has always appealed is the separation of 
replication from failover functionality.  I wouldn't want to change that for 
the world, and I don't want you to build anything into Slony that does 
network monitoring.

But I do think that it's still a legitimate question to ask: given two 
nodes, one of which used to be the provider, and the other of which used to 
be a receiver but has become provider by the execution of a failover 
command, can I tell that has happened by connecting only to the original 
provider?

> When your "network monitor" detects that either the client or node 2 can't 
> talk to node 1 any more, "it" has to make sure that they will not do so 
> all of the sudden (reconfigure switches or iptables), fire the slonik 
> script telling node 2 to take over, and reconfigure something like pgpool 
> to redirect the client to the new master.

I think you're making an assumption that it is desirable or even possible to 
do that in one process.  What I'm trying to do is separate the middle 
fire-the-failover-script step from the configuration of an interface like 
pg_pool.  When the cluster is functioning normally, the interface can work 
out the master-slave configuration for itself and so can be stateless, in 
the sense of not having to read a resource that says "the master is now this 
one". I'd like it to be able to do that after failover too.

Julian Scarfe