On Nov 21, 2012, at 4:49 PM, Mircea Markus <mmar...@redhat.com> wrote:
> 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).
^ At first glance, that's how I'd have implemented this feature, but Manik went
down the route of wrapping in futures only those operations that went remote.
Maybe he was worried about ctx switch cost? Or maybe about ownership of locks
when these are acquired in a separate thread from the actual caller thread?
> 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
^ To be precise, we don't build a class loaders. I guess you're refering at
building the invocation context.
These days we're more tight wrt the classloader used, avoiding the reliance on
the TCCL, so I think we're in a safer position.
> - 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.
^ I don't think this is crucial. You need to call future.get() to find out if
things worked correctly or not, regardless of cause.
> - 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.
^ Have you done some experimenting already?
Cheers,
>
> Cheers,
> --
> Mircea Markus
> Infinispan lead (www.infinispan.org)
>
>
>
>
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--
Galder Zamarreño
gal...@redhat.com
twitter.com/galderz
Project Lead, Escalante
http://escalante.io
Engineer, Infinispan
http://infinispan.org
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