[jbosscache-dev] Handling invalid nodes

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(a)jboss.org