Hi Douglas, you might have a look at memcached-session-manager [1] which is a tomcat session manager that stores sessions additionally in memcached (sessions are still kept in and read from local memory for best performance).
The session serialization is pluggable and there's an xml based serialization strategy (using javolution) to support code upgrade - of course you still have to keep track of code changes so that "old" session data structures can be deserialized to new data structures (have a look at [2] for serialization strategies). Btw, what I wonder: tomcat's session replication requires a session.setAttribute to detect a session modification and trigger a replication - is this requirement met by wicket? And apart from wicket, to me this seems to be a rather hard requirement for web applications. Who can guarantee, that nobody is getting a session attribute and modifying it without invoking session.setAttribute afterwards...? Right now I'm implementing a feature so that sessions are only sent to memcached if the session data changed. This is completely transparent, so that you might retrieve a complex session attribute, change some property of it and this change will be detected so that the session will be updated in memcached (more details on this can be found at [3]). Cheers, Martin [1] http://code.google.com/p/memcached-session-manager/ [2] http://code.google.com/p/memcached-session-manager/wiki/SerializationStrategies [3] http://code.google.com/p/memcached-session-manager/issues/detail?id=36 On Fri, 2010-03-05 at 12:15 -0800, Douglas Ferguson wrote: > I'm considering a 0 downtime deployment but am concerned with the amount of > state in the wicket session. > > This is the scenario that concerns me. > > 1) There are 2 tomcats running > 2) A change is made to a serializable object and the serial version id is > updated > 3) 1 tomcat instance is taken down for updating > 4) tomcat instance comes back up with new object and now tries to update > state from other tomcat and the wicket session has a reference to the old > version of the serializable. > > On Mar 5, 2010, at 12:18 PM, Igor Vaynberg wrote: > > > yes > > > > -igor > > > > On Fri, Mar 5, 2010 at 10:02 AM, Douglas Ferguson > > <[email protected]> wrote: > >> Has anybody had success with wicket using tomcat's session replication? > >> > >> D/ > > --------------------------------------------------------------------- > To unsubscribe, e-mail: [email protected] > For additional commands, e-mail: [email protected] > -- Martin Grotzke http://www.javakaffee.de/blog/
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