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From Filip Hanik - Dev Lists <>
Subject Re: Cluster Memory Leak - ClusterData and LinkObject classes
Date Tue, 01 Apr 2008 00:37:10 GMT
David Rees wrote:
> On Mon, Mar 31, 2008 at 4:48 PM, Filip Hanik - Dev Lists
> <> wrote:
>> David Rees wrote:
>>  > One problem I've intermittently had with clustering is that after a
>>  > Tomcat restart (we shut down one node and it immediately restarts,
>>  > generally within 30 seconds), they two nodes don't consistently sync
>>  > up. (The restarted node would not have the sessions from the other
>>  > node, but new sessions would get replicated over) I have to think that
>>  > this may be related to this issue.
>>  I believe you have to wait at least 30seconds before you bring up the
>>  other node.
>>  especially, if you are using mcastDropTime="30000" (could be the
>>  default?) then your nodes wont even realize this one is gone, and when
>>  you bring it back up within 30seconds, to the other nodes its like
>>  nothing ever changed.
> OK, I'll have to try to figure out how to keep Tomcat from starting up
> until 30 seconds have passed, then. Seems like this type of limitation
> deserved a big fat warning in the Cluster HOW-TO? Do you think that
> this could trigger the Queue build-up issue?
my guess is no, queue build up would be somewhere else.
>>  As rainer mentioned, if you are just starting to use cluster, switch to
>>  TC6 to avoid the migration you will have to make. TC6 also handles this
>>  scenario regardless of what you set your droptime to
> I'd like to migration to TC6, but that also means that we have to
> perform full validation testing which takes time and effort... Not to
> mention that it seems that TC6 has only recently stabilized compared
> to TC5. But it's good to know that TC6 resolves this issue. Can you
> explain the features in TC6 which prevents this from being an issue?
in TC6 a member/node receives a unique ID each time the JVM starts up 
and the member is created
in TC5.5 a member is identified by IP:listenPort, and that is the same 
each time you restart a tomcat, in TC6, it also uses the unique ID, so 
in tomcat 6, it does recognize the difference between a node process 
restarted vs a node just got disconnected from the network

> -Dave
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