[jbosscache-dev] Handling invalid nodes

[Mircea Markus]

What about doing the isInvalid check(and exception throwing ) in an 
interceptor that would be AFTER the CacheLoaderInterceptor? Phps 
CallInterceptor?


Manik Surtani wrote:
> Guys,
>
> I've been thinking about behaviour with the Node API, and wonder what 
> works best from a user standpoint.  Consider:
>
> * User gets a hold of a node and holds on to the ref for performance 
> reasons (Node n = cache.getNode(fqn))
> * Performs tasks on the node: n.put(), n.get(), etc.
> * Node checks for validity before performing any API calls, throwing a 
> NodeNotValidException if the node is not valid anymore.
>
> Nodes get marked as invalid if they are removed or moved by a 
> concurrent thread, or invalidated by a remote one.  Eviction did not 
> mark a node as invalid, but I think this is inconsistent and a bug: 
> eviction too should mark the node as invalid.
>
> So the question is this - with potentially likely events marking a 
> node as invalid - especially with eviction - should we throw a 
> NodeNotValidException?  Since (as of 2.1.0), the Node implementation 
> that a user has is an instance of NodeInvocationDelegate which in turn 
> has a reference to an UnversionedNode, perhaps we should handle the 
> NNVE within the NodeInvocationDelegate and perform a lookup internally 
> and refresh the UnversionedNode reference, and THEN throw a NNVE if we 
> can't fetch the node?
>
> Th drawback is that this is potentially two calls for what should be 
> one - node gets evicted, we call cache.getNode() internally to refresh 
> the reference (from a cache loader, etc), and then invoke whatever 
> call the user intended to call up the interceptor chain.  The benefit 
> is a smoother user experience.
>
> Thoughts/opinions?
>
> Cheers,
> -- 
> Manik Surtani
> Lead, JBoss Cache
> manik at jboss.org
>
>
>
>
>
>
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