RE: [jbosscache-dev] JBCACHE-388 Provide modified data in callbacks

This issue is relevant for DistributedState in AS 5.0 where the implementation was rewritten to use TreeCache for the underlying replicated store. There's currently a mismatch between the events published by DistributedState and those offered by TreeCache. Specifically, DistributedState identifies the data key and new value for modified categories (which are TreeCache nodes); it also identifies keys that are removed. Currently it's not possible to obtain this information from TreeCache unless the subscriber responds to the "pre" and "post" modification events by retrieving the modified node's Map before/after and then performing a diff operation. I've looked at the new CacheListener interface and it looks like it helps a little since it provides the Map as part of the event. But as Ben pointed out, it's still necessary for the subscriber to diff the maps to determine what was changed. So this doesn't appear to help significantly for DistributedState as the hard part is performing the diff, not retrieving the map. Jerry How common is the use case where the listener wants to know the differences? I'd be concerned about the overhead of creating objects to encapsulate the diff every time there is a change -- just so those objects can be passed to a CacheListener that ignores the data. OTOH, even if the current approach of just handing out the new data map is used, that should at least be a Collections.unmodifiableMap wrapping the internal data structure, so there's overhead there as well. Probably a wash, except in the put(Fqn, Map) case, where doing the diff is more tedious. I guess I have no strong opinion on this... jbosscache-dev-bounces(a)lists.jboss.org wrote: the I it Is _______________________________________________ jbosscache-dev mailing list jbosscache-dev(a)lists.jboss.org https://lists.jboss.org/mailman/listinfo/jbosscache-dev