[user] Re: async call issue

I think I found the cause for this behavior. Basically Lingo creates only one JMS session for the "server" /consumer which is exported via org.logicblaze.lingo.jms.JmsServiceExporter and a JMS Session essentially is required to (per jms spec) serialize execution of consumer message listeners.

 

This behaviour does not map well to the semantics of asynchronous calls which Lingo provides as the remoting provider. (alteast based on my interpretation of expected behavior).

 

There are a couple of possible solutions that I can think of right now :

 

The single consumer on the server side should simply add requests to a thread pool for execution.. This would effectively translate to a JMS Session which does not serialize execution of registered listeners. Webmethods has a flag which allows you to change the behavior from serialized to pooled execution. This behaviour translates better to a remote method invocation protocol.

 

The other options is that Lingo creates a separate session-destination for each method in the exported service. This way each method call on the service API (potentailly from different clients) does not block for other method calls to complete. This option is not as good as the first one as the same method call from different clients will be serialized.

 

Let me know your thoughts.

 

Sanjiv
 

On 5/13/06, Sanjiv Jivan <sanjiv.jivan@...> wrote:

I decided to upgrade to the latest Lingo/Active MQ CVS versions and see if that helps resolve this issue. I noticed that in the test case

 

\src\test\org\logicblaze\lingo\example\ExampleTest.java

 

the asynchronous test case "testAsyncRequestResponse" has been disabled.

 

 public void TODO_testAsyncRequestResponse() throws Exception {

..

 }

 

Was there any reason for doing this? Are they any known issues with asynchronous calls?

 

The issue I've encountered is a show stopper for us. The asynchronous call returns control to the client but not further calls to the server are not possible while the previous method call is still executing on the server. I'm trying to debug this issue myself but would appreciate some comments/investigation from the Lingo team as well.

 

Thanks,

Sanjiv

 

---------- Forwarded message ----------
From: Sanjiv Jivan <sanjiv.jivan@...>
Date: May 9, 2006 2:49 PM
Subject: Re: async call issue
To: user@...

 

I should mention that I ran the test under a debugger but wasn't able to pin point the issue. The source of the issue seems to be with the temporary queues created/shared in MultiplexingRequestor.

 

On 5/9/06, Sanjiv Jivan <sanjiv.jivan@...> wrote:

Hi,

I created an issue for this but figured I'd post my question incase anyone else had encountered a similar issue.

 

Making an async call to a service prevents subsequent calls to the service from being made prior to when the async method on the server completes execution.

Consider the Lingo test case org.logicblaze.lingo.example.ExampleTest#testClient

Change the delay in ExampleServiceImpl.asyncRequestResponse(String stock, ResultListener listener) to 35 seconds.

public void testClient() throws Exception {
   // START SNIPPET: simple

   // lets lookup the client in Spring
   // (we could be using DI here instead)
   ExampleService service = (ExampleService) getBean("client");

   // regular synchronous request-response
   int i = service.regularRPC("Foo");
   System.out.println("Found result: " + i);

   // async request-response
   TestResultListener listener = new TestResultListener();
   service.asyncRequestResponse("IBM", listener);

   //------------> sanjiv : new test code
   int ret = service.regularRPC("foo");
   System.out.println("return value is " + ret);
   //------------> sanjiv : end new test code

   // the server side will now invoke the listener
   // objects's methods asynchronously
   // END SNIPPET: simple

   listener.waitForAsyncResponses(2);

   System.out.println("Found results: " + listener.getResults());
}

In the example above, the async call is made (which runs for 35 seconds on the "server"). However when the next call of "ret = service.regularRPC("foo");" is made on the client, it blocks and eventually times out.

If we call an asynchronous call instead of service.regularRPC, that message is never received by the server.

This is the same behaviour when the destination is a Queue or a Topic.

 

Thanks,

Sanjiv