@Stephan
Both scenario 1 and 2 will be scalable because your controller methods can complete quickly and the hard work is done in a separate thread.

However, in scenario 2 you also get the benefit of leaving the response open after your controller method completes. This allows you to keep writing to it from the other thread. That is not possible in scenario 1.

Will there be something like ThreadLocal for these requests, but that spans the whole request? Like RequestLocal or something similar.

This is fantastic. There are so many areas where this will be extremely useful.

Hi Rossen,

Greate Post!

I tried your example for asychronous support. The container didn't start the new thread and didn't invoke the call() method. However it did print the request async support=true and async started=ture. After that its irgnoring return Callable() statement and expecting "process.jsp" as a view. So I am getting 404 error.

I configured async-supported=true for DispatchServlet in the web.xml.

Here is my controller method :

@RequestMapping(method = RequestMethod.POST, value="process")
public Callable process(final Model model, HttpServletRequest request) {
System.out.println("request asyncronouus support=" request.isAsyncSupported());
System.out.println("request asyncronouus started=" request.isAsyncStarted());
return new Callable() {
public String call() throws Exception {
System.out.println("entered call() method");
// Process input file..
//Thread.sleep(5000L);
String processName = _service.process("process");
model.addAttribute("message", "processMVC():name=" processName);
return "index";
}
};

}

Please let me know what is the issue here.
when you guys are expecting to release these changes?

I rather excited about this feature however I think it will require more work outside of the MVC layer to get it to work. At one point I was even trying to make my own AnnotationHandler that used Atmosphere till I ran into the ThreadLocal issue.

As mentioned earlier the ThreadLocal lifecycle is what concerns me most. I'm really hoping that this feature perhaps surfaces a generalized solution for Threadlocal management.

Right now Threadlocal is used in the TransactionSynchronizationManager, Spring Security and for some JSF things. Each of theses manage threadlocal in their own way. I believe we need a sort of Subscriber/Publisher pattern where different things know when to load/unload their Threadlocal data.

Whatever the solution I believe for complete usability with the existing spring framework some solution to the threadlocal issue needs to be addressed.

Hi Rossen

I have a question. Can i cancel this AsyncRequest from another Request.Think of this usecase.I have a high-computing action and i want to provide cancel option for this.How can i achieve this using Async support?

How does this feature compare to Asynchronous Controller in ASP.NET?

Hi Rossen,
This is exactly what i was looking for. I have started looking at PlayFramework. How is this new @Async support compared to what PlayFramework provides?

My Questions are
1) Are you using JBoss's NettyIO?
2) Who should manage the thread pool that is used to execute async requests?
3) Is this how the whole model looks like?
a) client sends request
b) Servlet thread starts processing.
c) Servlet thread makes an Async remote Rest call.
d) Servlet thread returns to serve other http connections.
e) Remote Http Call returns and an async thread is created to pack construct the response and sends it to the client.
Thanks
sri

Hi Rossen,

I've tried running the spring-mvc-async from a STS IDE VmWare vFabric tc Server Developer Edition and I am getting this exception.

org.springframework.web.util.NestedServletException: Request processing failed; nested exception is java.lang.IllegalStateException:
Async support must be enabled on a servlet and for all filters involved in async request processing.
This is done in Java code using the Servlet API or by adding
"true" to servlet and filter declarations in web.xml.
at org.springframework.web.servlet.FrameworkServlet.finalizeProcessing(FrameworkServlet.java:977)
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:923)
at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:801)

Please help. Thank you

Regards,
Alvin

Rossen,

Further to my prior email, I must mention that I don't see any such line as this

16:19:23 [SimpleAsyncTaskExecutor-1] DispatcherServlet

in the Tomcat 7.0.30 console.

Also, the browser hangs for the 3 seconds specified in the call() method.

Is this the expected behavior?

Julien.

There certainly wasn't any [MvcAsyncX] log in my Tomcat console. Only the usual synchronous tomcat logs. Never mind. I'll wait for the next article/post about this very interesting topic. Regards.

Please ignore my previous post. It has nothing to do with chunked encoding. What I was experiencing was making multiple requests to the same REST endpoint in the same browser. It appears all browsers make requests to the same url in a sequential manner, due to caching implementations. Nothing wrong with Spring.

Hi,

I thought the idea of comet was to allow a large number of requests to remain open, where the cost of each request was just the socket (i.e. not thread per connection, which is much more expensive). While this feature makes the requests async from the perspective of tomcat threads, there is still a thread per request (presumably spring is managing a cachedThreadPool)? Is the point of this feature really just to hack an unbounded thread pool on top of tomcat's fixed thread pool?

@Rossen I'm personally (you asked the community for feedback) much more interested in DeferredResult aka AMQP/JMS support. Especially AMQP as I think Spring's RabbitMQ support was a good move and we use/love RabbitMQ. It is superior to JMS.

The alternative of just returning some Future and putting into a different Thread pool does not interest me. An out of the box RabbitMQ with Spring MVC chat like app I think would be a killer demo. Its also whats missing as Atmosphere already has "Broadcasters" for Redis and JMS.

I can help participate in writing an example or app (or even maven archetype) if others are not already working on it.

Can DeferredResult object be reused?

Greets,

How can i jusy return an HttpStatus on success from an async hbase put?
By using DeferredResult ?

I have an async serverside proceasing -a db write.
On fail i will just call deferredRes.onError(throwable) and that will ttansparently go thru my apring configures ExceptionResolver to figure out some 50x return status.

Now i just wonder how to efficiently return a 204 on success….or how to redirect to other controller method annotated to return 204..for tjat i use SmartView namely RrdirectView?

What type T other than String is supported by DeferredResult generic type?
I would use a HttpStatus for sucess..or a RedirectView to a controller merhod which would return 204 status

Hi. The following responds 200 on second dispatch spring says "Null modelView, assuming done".
When debugging, i saw that the deferredResult had no resultHandler set.

@RequestMapping(value = STREAM_PATH, method = RequestMethod.POST)
@ResponseBody
public DeferredResult<ResponseEntity> heartbeat(@PathVariable(DEVICE_ID) String deviceId,..){
..
final DeferredResult<ResponseEntity> deferredResult = new DeferredResult<ResponseEntity>();
heartRateMonitor.heartbeat(deviceId, streamId, duration, until).setFutureMutationListener(
new FutureMutationListener() {
@Override
public void done() {
deferredResult.setResult(new ResponseEntity("", HttpStatus.NO_CONTENT));
}

@Override
public void failedOn(Throwable e) {
deferredResult.setErrorResult(e);
}
});
}
Please help:)