[jboss-jira] [JBoss JIRA] Commented: (JBAS-3473) Fix DistributedStateImpl.nodeRemove

[Jerry Gauthier (JIRA)]

    [ http://jira.jboss.com/jira/browse/JBAS-3473?page=comments#action_12346033 ] 
            
Jerry Gauthier commented on JBAS-3473:
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I've modified DistributedStateImpl so that it no longer issues duplicate notifications.  This change has been checked in.

This issue remains open due to problems with listeners that broadcast modification and removal events from remote nodes.  Final resolution of these issues depends on how JBossCache handles JBCACHE-388.  Currently JBossCache only broadcasts changes to Nodes and the cache-based DistributedState implementation maps Nodes to categories.  The JBossCache notifications don't specify what changes have been made to Nodes so DistributedStateImpl can't determine what keys have been modified or removed.  Since DistributedStateImpl relies on JBossCache to notify it of changes on remote cluster nodes, it's unable to broadcast events properly.

There are three possible solutions here.

1) JBossCache 2.0 *may* specify what's changed when a node is modified.  See JBCACHE-388 for further details on this.  If this information is available, DistributedState can simply rebroadcast the notifications received from JBossCache.

2) JBossCache provides "pre" and "post" event notifications.  DistributedState could retrieve the two maps and differentiate them to determine what data elements have been modified or removed.

3) DistributedState currently stores categories as nodes in JBossCache.  Keys are then stored as data elements in maps associated with the nodes.  Keys could alternatively be stored as nodes with each key having a map with the key and value stored in it.  This would be a less efficient use of JBossCache but it would ensure that DistributedState can identify key changes made on remote nodes.

Note that this issue only applies to notifications related to changes made on remote nodes.  Changes made on a local node are broadcast directly from DistributedSate and any local events received from JBossCache are simply ignored.





> Fix DistributedStateImpl.nodeRemove
> -----------------------------------
>
>                 Key: JBAS-3473
>                 URL: http://jira.jboss.com/jira/browse/JBAS-3473
>             Project: JBoss Application Server
>          Issue Type: Task
>      Security Level: Public(Everyone can see) 
>          Components: Clustering
>            Reporter: Brian Stansberry
>         Assigned To: Jerry Gauthier
>             Fix For: JBossAS-5.0.0.Beta
>
>
> AFAICT, this is not correct.  Key/value pairs are stored in the category node's data map; nodeRemoved treats things as if each key is its own node.
> Actually, I think the node per key approach is correct, until TreeCacheListener can provide info on what data was changed.
> Also, remove() itself notifies listeners of a removal, and then the listener does as well.  Needs to be one or the other; probably nodeRemoved() as that gets called for both local and remote removes.

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