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From Mark Thomas <>
Subject Re: Proposal: Some todo's at AsyncContext detected...
Date Wed, 30 Jun 2010 18:03:08 GMT
On 30/06/2010 17:01, Marc Guillemot wrote:
> Hi,
> What you write means that the freshly release Tomcat 7 doesn't fully
> implement Servlet API 3.0, isn't it?
> Interesting to see that nobody reacts :-(

If you were following the dev list you would have seen that 
Jean-Frederic has already vetoed the change Peter made on the basis that 
it breaks the TCK. That suggests that Peter's analysis of the current 
situation is not 100% correct.

My recollection is that the last thing that Filip implemented for 
Servlet 3.0 was the necessary timeout features. I'd be surprised if 
Filip, as a member of the Servlet Expert Group that wrote the spec, 
missed something fundamental. I wouldn't be surprised if there were some 
edge cases missed. I do know that Filip tended to leave a lot of the 
Servlet 3.0 TODOs in the code, even when he had implemented the 
appropriate feature. Those certainly need cleaning up.

Looking at Peter's test case - along with the other issues folks have 
raised in Bugzilla for the 7.0.0 release - is on my todo list but like 
the other committers I have a day job. Whilst many of the committers are 
fortunate enough (me included) to be able to allocate some work time to 
Tomcat development, it doesn't follow one of the other committers will 
immediately have the time necessary to look at Peter's e-mail and 
comment in detail. I can't speak for the others, but my free time is 
currently occupied with another Tomcat 7 issue - namely

Like any area of Tomcat, help is always appreciated. If you are 
interested in this issue and would like to help out I would encourage 
you to look at Peter's test case, compare the expected behaviour to what 
the spec defines and offer your view on whether there is a bug that 
needs fixing or not. If there is an issue, patches would be even better.


> Cheers,
> Marc.
> Peter Roßbach wrote:
>> Hi!
>> I detected some Todo's at AsyncContext
>> - AsyncContext.createListener
>> We don't make a resource injection or make it configurable!
>> Servlet 3.0 API comment:
>> "This method supports resource injection if the given clazz represents
>> a Managed Bean. See the Java EE platform and JSR 299 specifications
>> for additional details about Managed Beans and resource injection."
>> - I miss the is[Started,Completed] methods at AsyncContext interface
>> The only way to detect a completed state at AsyncContext inside an
>> AsyncListener is:
>> if (ac.getResponse() != null)
>> AsyncListener got an event, with empty state... -- Very strange!
>> Can't we clear all AsyncListener after send complete and before we
>> refresh the AsyncContext state?
>> How can a user handle a completed situation?
>> see o.a.c.core.TestAsyncListener
>> - AsyncContext.start() dosen't really start a thread!
>> We create wrapper of a Runnable, but we don't start a thread...
>> Error handling seam a little bit strange.
>> We only throw a RuntimeException(ex) and log an error!
>> Servlet API comment:
>> "Causes the container to dispatch a thread, possibly from a managed
>> thread pool, to run the specified Runnable. The container may
>> propagate appropriate contextual information to the Runnable."
>> How can we implement that?
>> Start everytime a new thread without pooling?
>> Use the connector executor pool from request?
>> Then we must extend the ProtocolHandler interface with getExecutor()
>> signature.
>> Use a separate Executor pool per Engine/Host or Context
>> How do we have to implemented the error handling?
>> - JioEndpoint has a timeout detection thread, but we don't start it!
>> I easy fix it with revision 958362,
>> but the polling strategy is slow and ineffectiv.
>> I didn't make a test at NIO/APR-HTTP or AJP-Connectors.
>> - After the timeout event is emitted, the completed method is
>> automatically called!
>> Servlet API 3.0 Spec says:
>> ====
>> ■In the event that an asynchronous operation times out, the container
>> must run
>> through the following steps:
>> ■ Invoke the AsyncListener.onTimeout method on all the AsyncListener
>> instances registered with the ServletRequest on which the asynchronous
>> operation was initiated.
>> ■ If none of the listeners called AsyncContext.complete() or any of the
>> AsyncContext.dispatch methods, perform an error dispatch with a status
>> code equal to HttpServletResponse.SC_INTERNAL_SERVER_ERROR.
>> ■ If no matching error page was found, or the error page did not call
>> AsyncContext.complete() or any of the AsyncContext.dispatch
>> methods, the container MUST call AsyncContext.complete().
>> ===
>> I miss the implementation that we call the error page!
>> - Currently a AsyncListener can't reinit a async cycle!
>> see o.a.c.connector.Request.startAsync
>> ... L1555ff
>> if (asyncContext==null) {
>> asyncContext = new AsyncContextImpl(this);
>> } else if (asyncContext.isStarted()) {
>> throw new IllegalStateException("Already started.");
>> }
>> ...
>> What does this spec definition really mean?
>> === Ch 2 Page 18
>> ■public void onStartAsync(AsyncEvent event) - Is used to notify the
>> listener that a new asynchronous cycle is being initiated via a call
>> to one of the
>> ServletRequest.startAsync methods. The AsyncContext corresponding
>> to the asynchronous operation that is being reinitialized may be
>> obtained by
>> calling AsyncEvent.getAsyncContext on the given event.
>> ====
>> - AsyncListener doesn't receive a onStartAsync event.
>> We don't implement it.
>> At AsyncListenerWrapper fireOnStartAsync is missing
>> As AsyncContext.startAsync method doesn't emit an event
>> - ContextClassLoader at AsyncContext.dispatch is not set!
>> I can't see that we correcly set the application ContextClassLoader
>> before
>> we dispatch the Request. What must we do at a CrossContext dispatch?
>> - After first complete async cycle, an AsyncListner receive
>> onStartAsync as code start next async cycle?
>> Why doesn't the Servlet 3.0 TCK check basic AsyncContext functionalities?
>> It seams that we better start a open test suite implementation at the
>> new Servlet 3.0 API.
>> Regards,
>> Peter
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