[jboss-user] [Clustering/JBoss] - Re: Sever Failover

[bstansberry@jboss.com]

Not easy to do reliably. :(

In 4.0.x, the master node is always the JGroups coordinator, which as I said is usually the node that's been running longest.  Usually but not always.  So, starting the node you want as master first is a quasi-solution

But, that's not very nice and isn't bulletproof, since if there is a disruption on the network, another server can become coordinator.  Plus if you need to restart the preferred master, it won't be coordinator again unless you restart all the nodes.

In 4.2 we introduced the ability to configure a pluggable policy for determining the master.  Pluggable = implement an interface and specify in the service.xml for your HASingleton the class of the impl.  There's no implementation yet of a policy that does what you want, though.  There's a JIRA for it: http://jira.jboss.com/jira/browse/JBAS-4228 and I'd be quite happy if someone from the community wanted to implement that.

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