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From "Rainer Jung" <tomcat-u...@kippdata.de>
Subject Re: DeltaManager for Clustering
Date Fri, 29 Jul 2005 21:01:04 GMT
> See, the thing is, we have a 3rd party library that saves information in
> the session.  It doesn't call setAttribute every time it changes the
> data.  DeltaManager appears to ignore the useDirtyFlag.  With
> SimpleTcpReplicationManager, I can set useDirtyFlag to false and we get
> the desired behavior.  With DeltaManager, the sessions get out of sync.
> So for the time being, I switched the managerClass back to
> SimpleTcpReplicationManager and things work the way they are supposed to.
>
> The issue is whether or not DeltaManager is supposed to use a
> useDirtyFlag or not I guess.  The config option is still there in the
> sample cluster config that comes with server.xml as well as in the
> online-documentation.  It has no effect though.

No, DeltaManager doesn't use that flag. It would somehow not make sense,
because the whole pupose of DeltaManager is to only replicate changed
attributes of a session and the flag tries to replicate every session
accessed. So if you would impement it with DeltaManager it would behave
the same way as the SimpleTcpReplicationManager already does.

Under high load that will be a problem. If that is relevant yu must do a
stress test and observe CPU/bandwidth/latency.

Maybe a crude workaround: at the end of the requst do a
getAttribute/setAttribute to the attributes you want to replicate. I think
DeltaManager does not really check for a change, it replicates all
attributes accessed via setAttribute.



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