[jbosscache-dev] easing the path for clients to get aroundredeployment class loading issues in JBC

[Galder Zamarreno]

I did suggest this to Manik, but he told me that marshalling would not work on local caches, but only in replicated ones. I might have misunderstood him.

The doc focuses on the state transfer issues when class loaders are not still available.

Galder Zamarreño
Sr. Software Maintenance Engineer
JBoss, a division of Red Hat


-----Original Message-----
From: Brian Stansberry 
Sent: 02 November 2006 15:58
To: Galder Zamarreno; jbosscache-dev at lists.jboss.org
Subject: RE: [jbosscache-dev] easing the path for clients to get aroundredeployment class loading issues in JBC

There's already an API for this kind of use case. I'm going to speak in 1.x terms here:

// Config for cache startup
TreeCache.setUseRegionBasedMarshalling(true);
TreeCache.inactiveOnStartup(true); // suppresses initial state transfer

// Deploy phase -- app creates a region and registers it's classloader
TreeCache.registerClassloader(Fqn, ClassLoader);
// Then transfer the state for the region, since you've now go the correct classloader
TreeCache.activateRegion(Fqn);

// Operate normallly

// Undeploy phase -- deactivate the region, which evicts all nodes
TreeCache.inactivateRegion(Fqn)
// Don't leak a classloader ref
TreeCache.unregisterClassloader(Fqn);

- Brian

jbosscache-dev-bounces at lists.jboss.org wrote:
> Hi,
> 
> I have seen couple of people with the same issue in the past
> few weeks. I already had a chat with Manik but it was more
> about solving the problem at the time rather than thinking
> how we can make it easier for the customers to get around it.
> 
> Applications which are redeployed and interact with the cache
> are quite likely to encounter class loading issues. They tend
> to enter data in the cache, they get redeployed, try
> accessing the data entered previously and you end up with a
> ClassCastException. 
> 
> For caches managed by Hibernate, this is not a problem cos
> Hibernate does the cleanup on undeployment, asking clients to close
> the session. 
> 
> In the rest of cases, clients have to iterate over evict()
> calls. This will be solved in JBC 2.0 with evictSubtree() method that
> can be recursive. 
> 
> However, clients still need to code an MBean which is part of
> the lifecycle of the deployment, and upon destroy, it calls
> evictSubtree(). 
> 
> The cache configuration would have to depend on this MBean in
> case the cache deployment is done inside the client's
> application. Otherwise, we could assume that undeployment of
> JBC is quite likely due to AS undeployment in which case there's no
> need for cleanup. 
> 
> Have you got any ideas of anything else that could be done in
> JBC to help speed up this implementation and make it less of
> daunting task for the customer?
> 
> I guess the main part is documenting all this.
> 
> Galder Zamarreño
> Sr. Software Maintenance Engineer
> JBoss, a division of Red Hat
> 
> 
> 
> _______________________________________________
> jbosscache-dev mailing list
> jbosscache-dev at lists.jboss.org
> https://lists.jboss.org/mailman/listinfo/jbosscache-dev



Brian Stansberry
Lead, AS Clustering
JBoss, a division of Red Hat
Ph: 510-396-3864
skype: bstansberry