[jbosscache-dev] Region.markNodeCurrentlyInUse

[Manik Surtani]

Sorry I've been out of this for a while (kind of shelved 2.0.0 issues  
so I could clear the stack of stuff sitting on top 1.3.0.SP4 and then  
1.4.1)

On 15 Nov 2006, at 14:51, Brian Stansberry wrote:

> The purpose of this method is to allow an application to signal the
> eviction policy to not evict a particular node who's data it's using.
> Needed in situations where the app doesn't hold a lock on the node  
> *and*
> where evicting the node will cause a problem.
>
> AFAICT, this use case is really just for EJB3 SFSBs, where the problem
> is that evicting an "in-use" node forces the container to call
> prePassivate() on the in-use EJB. This is done from a CacheListener.
>
> This is all a bit funky.  Adding methods to the API to deal with a  
> very
> specific use case.  It also has a small race condition, which I won't
> get into here.
>
> Here's a different (but still funky) approach:
>
> Add a new exception class o.j.c.eviction.NodeInUseException extends
> RuntimeException.
>
> The application implements CacheListener. When it gets a
> nodePassivated(pre=true) event, if it doesn't want the passivation, it
> throws the NodeInUseException.  This will abort the eviction and
> propagate back to the eviction policy.  Eviction policies are already
> written such that they catch all exceptions, and then throw the node
> into a retry queue (see BaseEvictionAlgorithm.evictCacheNode()). If we
> wanted to get fancy, we could specifically catch NodeInUseException  
> and
> decide from there whether to add it to the retry queue.
>
> I don't think we should try to change this this week; more of a short
> term future thing.
>
> Thoughts?

Your second (and still funky) approach does seem a lot cleaner than  
hacking in stuff into the API for a very specific use case.  So  
certainly my preferred option.  But from a performance standpoint, is  
this really an "exceptional" circumstance?

>
> Brian Stansberry
> Lead, AS Clustering
> JBoss, a division of Red Hat
> Ph: 510-396-3864
> skype: bstansberry
>
> IT executives: Red Hat still #1 for value
> http://www.redhat.com/promo/vendor/
>
> _______________________________________________
> jbosscache-dev mailing list
> jbosscache-dev at lists.jboss.org
> https://lists.jboss.org/mailman/listinfo/jbosscache-dev