Resteasy is using org.jboss.resteasy.plugins.server.servlet.HttpServlet30Dispatcher in processing @Suspended.
We use it in test cases here, ./testsuite/integration-tests/src/test/resources/org/jboss/resteasy/test/asynch


----- Original Message -----

From: "Steven Schlansker" <sschlansker@opentable.com>
To: resteasy-dev@lists.jboss.org
Sent: Tuesday, October 11, 2016 7:16:29 PM
Subject: Re: [resteasy-dev] RESTEasy asynchronous processing with @Suspended -- actually synchronous?

Hi again,

I was somewhat disappointed to not get an answer here, but I did a fair
amount more digging,
and managed to find Filter30Dispatcher (which just moved recently for
upcoming 3.1.0)

Unfortunately then I found that the documentation does not mention this
class at all, but at least it exists!
(at least not on
http://docs.jboss.org/resteasy/docs/3.0.19.Final/userguide/html_single/index.html
)

So far it seems to work well.  Better than FilterDispatcher, at least :)
Let me know if there's any gotchas or other bits that I've missed.

Best,
Steven

On Oct 7, 2016, at 1:21 PM, Steven Schlansker <sschlansker@opentable.com>
wrote:

[ apologies for the rampant cross-posting, it looks like I might have been
sending this to old mailing lists, and getting lost in the void? ]

Hello resteasy-dev,

I am trying to use the new JAX-RS 2.0 @Suspended AsyncResponse mechanism to
write
a service that expects many idling connections (awaiting an event via
long-poll),
and therefore seems like a good candidate for asynchronous responses, so as
not
to use a large number of waiting threads.

The resource code is very simple:

 @GET
 @Produces(MediaType.APPLICATION_JSON)
 public void watchForChanges(
         @Suspended AsyncResponse asyncResponse,
         @QueryParam("since") long since)
 {
     controller.watchForChanges(since, asyncResponse::resume);
 }

The intent is that watchForChanges places the (inferred)
Consumer<ResponseObject> on a queue,
and returns immediately.  Later on a background thread comes by and
completes the request.

However, when testing with say 20 clients, it sure looks like the end
result is still a
thread per request model:


"qtp1718322084-43" - Thread t@43
java.lang.Thread.State: WAITING
	at sun.misc.Unsafe.park(Native Method)
	- parking to wait for <3537ebd5> (a
	java.util.concurrent.CountDownLatch$Sync)
	at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
	at
	java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(AbstractQueuedSynchronizer.java:836)
	at
	java.util.concurrent.locks.AbstractQueuedSynchronizer.doAcquireSharedInterruptibly(AbstractQueuedSynchronizer.java:997)
	at
	java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireSharedInterruptibly(AbstractQueuedSynchronizer.java:1304)
	at java.util.concurrent.CountDownLatch.await(CountDownLatch.java:231)
	at
	org.jboss.resteasy.core.SynchronousExecutionContext$SynchronousAsynchronousResponse.initialRequestThreadFinished(SynchronousExecutionContext.java:127)
	at
	org.jboss.resteasy.core.SynchronousDispatcher.invoke(SynchronousDispatcher.java:411)
	at
	org.jboss.resteasy.core.SynchronousDispatcher.invokePropagateNotFound(SynchronousDispatcher.java:247)
	at
	org.jboss.resteasy.plugins.server.servlet.ServletContainerDispatcher.service(ServletContainerDispatcher.java:225)
	at
	org.jboss.resteasy.plugins.server.servlet.FilterDispatcher.doFilter(FilterDispatcher.java:62)
	at
	org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1676)
<snip Jetty handler / filter chain>
	at org.eclipse.jetty.server.HttpChannel.handle(HttpChannel.java:319)
	at
	org.eclipse.jetty.server.HttpConnection.onFillable(HttpConnection.java:253)
	at
	org.eclipse.jetty.io.AbstractConnection$ReadCallback.succeeded(AbstractConnection.java:273)
	at org.eclipse.jetty.io.FillInterest.fillable(FillInterest.java:95)
	at
	org.eclipse.jetty.io.SelectChannelEndPoint$2.run(SelectChannelEndPoint.java:93)
	at
	org.eclipse.jetty.util.thread.strategy.ExecuteProduceConsume.executeProduceConsume(ExecuteProduceConsume.java:303)
	at
	org.eclipse.jetty.util.thread.strategy.ExecuteProduceConsume.produceConsume(ExecuteProduceConsume.java:148)
	at
	org.eclipse.jetty.util.thread.strategy.ExecuteProduceConsume.run(ExecuteProduceConsume.java:136)
	at
	org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:671)
	at
	org.eclipse.jetty.util.thread.QueuedThreadPool$2.run(QueuedThreadPool.java:589)
	at java.lang.Thread.run(Thread.java:745)



The concept of a "SynchronousAsynchronousResponse" and implementation of in
particular SynchronousDispatcher#invoke seem to be totally not what I
want:
         /**
          * Callback by the initial calling thread.  This callback will
          probably do nothing in an asynchronous environment
          * but will be used to simulate AsynchronousResponse in vanilla
          Servlet containers that do not support
          * asychronous HTTP.
          *
          */
         request.getAsyncContext().getAsyncResponse().initialRequestThreadFinished();


What am I doing wrong?  How do I get truly asynchronous processing?

This is with RESTEasy 3.0.18 running on Jetty 9.3.11

Thanks for any advice,
Steven

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