[jboss-dev-forums] [Design of Clustering on JBoss (Clusters/JBoss)] - Re: HASingleton and partition merges

[adrian@jboss.org]

"galder.zamarreno at jboss.com" wrote : I think it needs configuring too but I would leave it as off by default so that it mantains previous 4.0.x behaivour and then customers can set it to true for recommended services, such as HA-JMS.
  | 
  | What complications can you see in backporting this? The patch instructions could explain the flag and give the recommendations.

If you make it configurable it should be *on* by default.

The main use of the deploy-hasingleton is for HA-JMS which needs this behaviour
(restart on merge).
The same will be true of any singleton that is not totally in-memory.

If somebody doesn't want this behaviour, they can always create their
own deploy-hasingleton-ignore-merge with the MBean configured not to restart.

The real solution (which I've advocated for a while) is for this behaviour
to be defined on the MBean so you could do something like:

  | <mbean ...>
  | <ha-singleton partition="DefaultPartition" restart-on-merge="true"/>
  | 

This is something that can be done in JBoss5 with the decorators (aspects)
and using an annotation rather than specific xml.


  | <bean ...>
  | <annotation>@org.jboss.cluster.annotation.HASingleton</annotation>
  | 
  | public @interface HASingleton
  | {
  |    String partiionName() default "DefaultPartition";
  |    boolean restartOnMerge() default true;
  | }
  | 
  | and even "programmatically":
  | 
  | @HASingleton
  | public class Queue {}
  | 


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