[jboss-dev-forums] [Design of Clustering on JBoss (Clusters/JBoss)] - Re: JBAS-4228 Preferred master node for HASingleton

[galder.zamarreno@jboss.com]

OK, no probs. Thanks for the heads up.

Had a quick look at implementing JBAS-5161 the other day and there're a couple of things I wanted to mention:

1.-  The intention of JBAS-4228, according to the JIRA, is that if a preferred master is there, use it, otherwise fall back on standard policy. The standard policy imo is the policy that should be applied when no election policies defined, which is, as per HASingletonSupport.partitionTopologyChanged(), :

isElectedNewMaster = isDRMMasterReplica();

So, I think we should have a default policy with this implemented and have PreferredMasterElectionPolicy extend it. 

The current implementation has the preferred master code included HASingletonElectionPolicyBase and if not defined, defaults on the abstract implementation of elect(). So, in reality is doing, if preferred master not available, leave it the election policy defined (for example, in the tests HASingletonElectionPolicySimple).

Personally, I'm more inclined to implementing the default policy in HASingletonElectionPolicyBase and PMEP extending it. Thoughts?

2.- Does PreferredMasterElectionPolicy need an MBean interface? We had a chat about this stuff in a previous forum post. I don't think there's a need to have an MBean interface at this level. If anyone wants to check or change this at runtime, this could be done via HASingletonSupportMBean.set/getElectionPolicy() bearing in mind that HASingletonControllerMBean extends HASingletonSupportMBean. Thoughts?

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