I have a fairly simple program that, so far, is based pretty much on
the sample c++ pub/sub code. I'm having an issue where QPID reports
"No listener found for destination" about half the time.
I have a subscription manager that's a factory style object. It holds
the connection and a session object created from that connection. It
creates Listener objects that are derived from the following base
class:
class QPListenerBase : public MessageListener {
private:
void received(Message& message);
protected:
Session& m_session;
SubscriptionManager m_subscriptions;
std::string m_GUID;
public:
QPListenerBase(Session& session);
virtual void prepareQueue(const std::string& routing_key);
virtual void listen();
virtual void unlisten();
virtual void waitforstop();
virtual void receiveMessage(Message& message);
virtual ~QPListenerBase() { };
};
I have specialized listeners that are subclasses of QPListenerBase.
My base received() simply calls the specialized receiveMessage() in
the subclasses.
The factory, when it creates a listener, initializes it using
prepareQueue() almost exactly as per the sample code:
void QPListenerBase::prepareQueue(const std::string& routing_key) {
std::string queue = "listener." + routing_key + "." + m_GUID;
m_session.queueDeclare(arg::queue=queue, arg::exclusive=true,
arg::autoDelete=true);
m_session.exchangeBind(arg::exchange = "amq.topic",
arg::queue=queue, arg::bindingKey=routing_key);
m_subscriptions.subscribe(*this, queue);
}
... and stores it in a vector of listeners as follows:
boost::shared_ptr<QPListenerBase> ptr(new QPListenerBase(m_session));
ptr->prepareQueue("channel.msgs." + senderGUID);
m_listeners.push_back(ptr);
(I'm using shared_ptr here because QPListenerBase, with its Session
reference, doesn't meet the stl criteria of being copyable, so I wrap
it in a shared_ptr, which is copyable).
When it's runtime I simply iterate over the listener collection and
ultimately call QPListenerBase.m_subscriptions.start()
I have a python test script that sends messages that should be picked
up by specific listeners. And they are, about half the time.
Here's what I get when I have two listeners listening on a topic
exchange. Messages are sent randomly to either channel.msgs.0 or
channel.msgs.1 here. The message content is a UUID. I first print
out the message in the base received() and then in my subclass
receiveMessage().
[received ef923fdc-83dd-4c54-875a-97e8be218860]:
a011bede-92cb-47a9-95d0-4125303b8cfd
[receiveMessage ef923fdc-83dd-4c54-875a-97e8be218860]:
a011bede-92cb-47a9-95d0-4125303b8cfd
2009-12-12 10:29:59 error No listener found for destination
listener.channel.msgs.1.ef923fdc-83dd-4c54-875a-97e8be218860
2009-12-12 10:30:04 error No listener found for destination
listener.channel.msgs.0.f7a20b18-9b30-4ada-abb5-a8bf492b5353
2009-12-12 10:30:09 error No listener found for destination
listener.channel.msgs.1.ef923fdc-83dd-4c54-875a-97e8be218860
[received ef923fdc-83dd-4c54-875a-97e8be218860]:
7e1426b1-fba7-4e70-969a-c0b726293ebb
[receiveMessage ef923fdc-83dd-4c54-875a-97e8be218860]:
7e1426b1-fba7-4e70-969a-c0b726293ebb
[received f7a20b18-9b30-4ada-abb5-a8bf492b5353]:
93ab5106-c774-419e-bf1d-4df99c5f97a1
[receiveMessage f7a20b18-9b30-4ada-abb5-a8bf492b5353]:
93ab5106-c774-419e-bf1d-4df99c5f97a1
[received ef923fdc-83dd-4c54-875a-97e8be218860]:
aeaa41a1-b709-4fde-8ca2-8cf650ec4baf
[receiveMessage ef923fdc-83dd-4c54-875a-97e8be218860]:
aeaa41a1-b709-4fde-8ca2-8cf650ec4baf
2009-12-12 10:30:29 error No listener found for destination
listener.channel.msgs.1.ef923fdc-83dd-4c54-875a-97e8be218860
2009-12-12 10:30:34 error No listener found for destination
listener.channel.msgs.0.f7a20b18-9b30-4ada-abb5-a8bf492b5353
Why are my listeners listening only half the time? Any ideas?
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