[jboss-dev-forums] [Design of JBossCache] - CacheListener notifications during data gravitation

[bstansberry@jboss.com]

Found an issue with BR and the AS web clustering code that's really a general problem with BR.

Issue is that both the http session repl code and clustered sso use cache listeners that interpret nodeRemoved calls as indicating a session/sso has been invalidated on another node.  They respond by invalidating on their own node.

Problem is the _dataGravitationCleanup call that's part of data gravitation also generates nodeRemoved calls.  But in that case, it's not appropriate for the cache listener to do anything.  This causes a less than ideal behavior with session repl and breaks clustered sso.

Right now there's no way for a cache listener to discriminate between the two cases.  One solution I thought of was to have TreeCache set a boolean value in a ThreadLocal in _clusteredGet and _dataGravitationCleanup.  A cache listener could then check for the ThreadLocal and ignore events that arise from data gravitation.

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