[jboss-dev-forums] [Design of Clustering on JBoss] - Re: JBAS-5703 - Make HA-JNDI use wait for first positive res

[bstansberry@jboss.com]

"galder.zamarreno at jboss.com" wrote : Re: https://jira.jboss.org/jira/browse/JBAS-5703
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  | I've attached a patch containing fix for this. Few notes:
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Great; thanks.

anonymous wrote : 1. I've tested this with a 3 node cluster (node1,node2 and node3) and two ejbs (ejbA and ejbB where ejbA calls ejbB via HAJNDI). Deployment wise, ejbA is deployed in node1 and ejbB is deployed in node3. I was able to make a call successfully via ejbA in node1 and was able to check via logs that once response from node3 was received, the lookup returned. Now, my question is, how to create a unit test around this? Not easy...

Testing can be done in layers:

a) Unit test your LookupSucceededFilter.  That's really the key thing here.
b) Unit test RspFilterAdapter.
c) A test of ClusterPartition.callMethodOnCluster where ResponseFilter param is passed. One way to do that at least partially is to have a service that calls method public boolean echo(boolean arg), where response is whatever arg was. Call with a filter that only accepts "true". Invoke method twice, passing "true" then "false"; should get a response to first call, none to second call.
d) A full test of the HA-JNDI functionality. That can wait until we make ClusterPartition more of a POJO, something where a couple can be instantiated in a unit test the way JBC can. You can file a JIRA to add such a test.

anonymous wrote : 2. I noted this as a todo in the patch: ResponseFilter/RspFilter API: If needMoreResponses() took response and sender as well, class implementations could be Immutable and same instance could be passed to all lookups. As it is right now, they can't and new instances need to be generated for every lookup.

Having 2 methods lets you filter responses out of the response list while still accepting more responses. To get the same thing out of one method you'd have to change the return type to something beyond simple boolean, perhaps Boolean but better an enum.  This would be a JGroups API change.

anonymous wrote : 3. Could response filtering done in ClusterPartition.processResponseList() be moved here? Any NoHandlerForRPC would be caught here immediately and could potentially avoid double processing. Thoughts?

Something to think about; could be done in RspFilterAdapter.

Hmm -- don't think it works well for the ordinary case where you want responses from everyone.  To return properly from needMoreResponses() the RspFilterAdapter would have to know how many responses it is expecting and count how many it has gotten. And deal with suspicions/view changes that may occur in the meantime.

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