[infinispan-dev] Refactoring async operations

[Mircea Markus]

Hi,

Part of fixing ISPN-2435, I need to significantly change DistributionInterceptor which at the moment is a very complex pice of code. Building the fix on top of it is extremely difficult and error prone, so I need to refactor it a bit before moving forward.
One such refactoring is about changing the way the async operations are handled (e.g. putAsync()). At the moment all the interceptor calls happen in user's thread, but two remote calls which are invoked with futures and aggregated:
the L1 invalidation and the actual distribution call. The code for handling this future aggregation is rather complicated and spreads over multiple classes (RpcManager, L1Manager, ReplicationInterceptor, DistributionInterceptor), so the simple alternative solution I have in mind is to build an asycPut on top of a syncPut and wrap it in a future:

CacheImpl:putAsync(k,v) {
    final InvocationContext ic = createInvocatinonContextInCallerThread(); //this is for class loading purpose
    return asyncPoolExecutor.submit(new Callable() {
         public Object call() {
             return put(k,v, ic); //this is the actual sync put
         }
    }   
} 

This would significantly simplify several components ( no references to network/aggregated futures in RpcManager, L1Manager, ReplicationInterceptor, DistributionInterceptor).
Possible issues:
- caller's class loader - the class loader is aggregated in the InvocationContext, so as long as we build the class loader in caller's thread we should be fine
- IsMarshallableInterceptor is used with async marshalling, in order to notify the user when objects added to the cache are not serializable. With the approach I suggested, for async calls only (e.g. putAsync) this notification would not happen in caller's thread, but async on future.get(). I really don't expect users to rely on this functionality, but something that would change never the less. 
- anything else you can think of?

I know this is a significant change at this stage in the project, so I really tried to go without it - but that resulted in spaghetti code taking a lot of time to patch. So instead of spending that time to code a complex hack I'd rather go for the simple and nice solution and add more unit tests to prove it works.

Cheers,
-- 
Mircea Markus
Infinispan lead (www.infinispan.org)




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