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From Gordon Sim <g...@redhat.com>
Subject Re: Request/response between .NET server and python client
Date Wed, 11 Aug 2010 10:17:20 GMT
On 08/11/2010 09:54 AM, Chris Howard wrote:
> Hi,
>
> I am having difficulty with sending a simple request/response between a
> server written in C# and a client written in python. I have no such
> problems when the client and server are both written in python. I am
> using qpid 0.7 (built from the trunk approx. 3 weeks ago)
>
> Here is the code for the C# server:
>
> try
> {
> Connection connection = new Connection("localhost:5672");
> connection.Open();
> Session session = connection.CreateSession();
> Receiver receiver = session.CreateReceiver("send ; {create: always,
> delete: always}");
>
> while (true)
> {
> Message request = receiver.Fetch(DurationConstants.FORVER);
> Sender sender = session.CreateSender(request.ReplyTo);
> Message response = new Message("pong");
> sender.Send(response);
> }
> }
> catch (System.Exception e)
> {
> Console.WriteLine(e.ToString());
> }
>
> And here is the code for the python client:
>
> import qpid.messaging
>
> connection = qpid.messaging.Connection('amqp://localhost:5672')
> connection.open()
> session = connection.session()
> receiver = session.receiver('#reply ; {create: always, delete: always}')
> sender = session.sender('send ; {create: always, delete: always}')
> request = qpid.messaging.Message(content = 'ping', reply_to =
> receiver.source)
> sender.send(request)
> response = receiver.fetch(10)
> print response.content
> connection.close()
>
> I start the server, and then start the client. The server receives the
> request from the client, but the call to CreateSender throws an
> exception with the message:
>
> "Exchange 9224f93b-8c4b-4675-bc04-61e721387140#reply does not exist"

This appears to me to be a bug in the python client in converting an 
address to an AMQP 0-10 reply-to struct. It is sending the reply-to as 
an exchange value:

  {MessageProperties: reply-to={ReplyTo: 
exchange=95004e55-23c9-4c41-acd0-bde7c09a6096#reply; }; 
application-headers={}; }

As it represents a queue, I believe the name should be sent as the 
routing-key of the reply-to struct, with the exchange left empty to 
refer to the default (nameless exchange). Certainly this is what the c++ 
client expects.

Rafi, do you agree?

> Furthermore, there is another exception thrown during program exit:
>
> Unhandled Exception: System.AccessViolationException: Attempted to read
> or write
> protected memory. This is often an indication that other memory is corrupt.
> at qpid.messaging.Message.{dtor}(Message* )
> at qpid.messaging.Message.__delDtor(Message* , UInt32 )
> at Org.Apache.Qpid.Messaging.Message.Cleanup()
> at Org.Apache.Qpid.Messaging.Message.!Message()
> at Org.Apache.Qpid.Messaging.Message.Dispose(Boolean )
> at Org.Apache.Qpid.Messaging.Message.Finalize()

This is a different issue and looks on first glance like a bug in the 
.NET 'binding' for the c++ implementation of the messaging API.

Chuck, any thoughts on this?

> Also, the output from the broker suggests that the queue /has /been
> created:
>
> 2010-08-11 09:44:37 info Queue
> "9224f93b-8c4b-4675-bc04-61e721387140#reply": Policy created:
> type=reject; maxCount=0; maxSize=104857600
> 2010-08-11 09:44:37 error Execution exception: not-found: Exchange not
> found: 9224f93b-8c4b-4675-bc04-61e721387140#reply
> (..\..\qpid\cpp\src\qpid\broker\ExchangeRegistry.cpp:92)
>
> Can anyone explain what I am doing wrong here? Or is this a bug?

It's a bug (perhaps two in fact!).

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