[infinispan-issues] [JBoss JIRA] (ISPN-1541) NotifyingNotifiableFuture's FutureListener can not invoke Future API on FutureListener#futureDone callback

[Vladimir Blagojevic (Commented) (JIRA)]

    [ https://issues.jboss.org/browse/ISPN-1541?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12645455#comment-12645455 ] 

Vladimir Blagojevic commented on ISPN-1541:
-------------------------------------------

It is a good idea but what about subclasses of NotifyingFutureImpl that override get?
                
> NotifyingNotifiableFuture's FutureListener can not invoke Future API on FutureListener#futureDone callback
> ----------------------------------------------------------------------------------------------------------
>
>                 Key: ISPN-1541
>                 URL: https://issues.jboss.org/browse/ISPN-1541
>             Project: Infinispan
>          Issue Type: Bug
>          Components: RPC
>    Affects Versions: 5.0.1.FINAL, 5.1.0.BETA4
>            Reporter: Vladimir Blagojevic
>            Assignee: Vladimir Blagojevic
>             Fix For: 5.1.0.FINAL
>
>
> Invoking Future#get from a FutureListener attached to a NotifyingNotifiableFuture passed as a parameter to RpcManager#invokeRemotelyInFuture throws InterruptedException! Sounds more complicated than it really is! In another words, the following code throws InterruptedException 
> {code}NotifyingFutureImpl f = ...
>       f.attachListener(new FutureListener<Object>() {
>          
>          @Override
>          public void futureDone(Future<Object> future) {
>             try {      
>                future.get();
>             } catch (Exception e) {   
>                e.printStackTrace();
>             }             
>          }
>       });
>       CommandsFactory cf = cache1.getAdvancedCache().getComponentRegistry().getComponent(CommandsFactory.class);
>       cache1.getAdvancedCache().getRpcManager().invokeRemotelyInFuture(null, cf.buildPutKeyValueCommand("k","v", -1, -1, null), f);
> {code}
> the reason why we get InterruptedException is that we invoke notifyDone which in turn invokes futureDone from *the same thread* invoking the future's callable. 
> {code}
>  public final void invokeRemotelyInFuture(final Collection<Address> recipients, final ReplicableCommand rpc, final boolean usePriorityQueue, final NotifyingNotifiableFuture<Object> l, final long timeout) {
>       if (trace) log.tracef("%s invoking in future call %s to recipient list %s", t.getAddress(), rpc, recipients);
>       final CountDownLatch futureSet = new CountDownLatch(1);
>       Callable<Object> c = new Callable<Object>() {
>          public Object call() throws Exception {
>             Object result = null;
>             try {
>                result = invokeRemotely(recipients, rpc, true, usePriorityQueue, timeout);
>             } finally {
>                try {
>                   futureSet.await();
>                } catch (InterruptedException e) {
>                   Thread.currentThread().interrupt();
>                } finally {
>                   l.notifyDone();
>                }
>             }
>             return result;
>          }
>       };
>       l.setNetworkFuture(asyncExecutor.submit(c));
>       futureSet.countDown();      
>    }
> {code}
> The solution is to wait for callable to finish and invoke notifyDone from the other thread. We have two choices here:
> a) invoke notifyDone from the same thread invoking invokeRemotelyInFuture. This in turn changes invokeRemotelyInFuture to be less async than it should be
> b) invoke callback on another thread
> {code}
> public final void invokeRemotelyInFuture(final Collection<Address> recipients,
>             final ReplicableCommand rpc, final boolean usePriorityQueue,
>             final NotifyingNotifiableFuture<Object> l, final long timeout) {
>       if (trace)
>          log.tracef("%s invoking in future call %s to recipient list %s", t.getAddress(), rpc,
>                   recipients);
>       final CountDownLatch callableCompleted = new CountDownLatch(1);
>       Callable<Object> c = new Callable<Object>() {
>          public Object call() throws Exception {
>             Object result = null;
>             try {
>                result = invokeRemotely(recipients, rpc, true, usePriorityQueue, timeout);
>             } finally {
>                callableCompleted.countDown();
>             }
>             return result;
>          }
>       };
>       l.setNetworkFuture(asyncExecutor.submit(c));
>       asyncExecutor.submit(new Runnable() {
>          
>          @Override
>          public void run() {
>             try {
>                callableCompleted.await();
>             } catch (Exception e) {
>             } finally {
>                l.notifyDone();
>             }       
>          }
>       });     
>    }
> {code}
> We can of course, leave things as they are right now but in such case we have to warn the implementer of FutureListener that he/she can not call future.get() from a FutureListener!

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