Qpid Proton Python detecting an empty queue in on_message

Question

I am using Qpid Proton using Python to consume messages from a queue in AMQ. I am learning this as I go - I am far from an expert at it so I am reaching out for some help. I have a situation where the AMQ queue holds messages that represent work to be done and it goes against a database (which takes time to do). So I am Receiving "N-number" of messages from the queue, doing the work, and repeat. The problem is I cant' figure out a way to know if the queue is empty...

Is there a way to detect if a queue in a broker is empty after the last message has been consumed? If this were a single-threaded consumer, then no problem; but I may have several consumers going against the one queue so knowing exactly how many messages are on the queue is not possible.

So for example, on the on_message method (this comes from the Qpid Python documentation (direct_recv.py) we have this:

    def on_message(self, event):
        if event.message.id and event.message.id < self.received:
            # ignore duplicate message
            return
        if self.expected == 0 or self.received < self.expected:
            print(event.message.body)
            self.received += 1
            if self.received == self.expected:
                event.receiver.close()
                event.connection.close()
                self.acceptor.close()

This fragment shows that when self.received == self.expected, then the consumer will close. For example, suppose a queue in a broker has 65 messages and the consumer calling this method sets self.expected = 25, then after 25 messages are consumed then this will end; I can make that work.

Now suppose the code tries to consume the same 25 messages (self.expected = 25), however the queue only has at that moment 12 messages then, the receiver will hang indefinitely - until more messages are added to the queue. However in my case, no more messages will be added.

Is there a way, to query the queue and determine if the queue is "empty" and if so, exit? In other words something like:

            if ( self.received == self.expected ) or (empty queue)
                event.receiver.close()
                event.connection.close()
                self.acceptor.close()

I just can't figure out how to know if the queue is empty. Is this even possible?

As a side note I am able to make this work by using a BlockingConnection. It is not as elegant as using the Receive class and is also not as fast. So essentially:

1. create the Blocking Connection
2. write a loop to receive and accept "N-number" of messages (or wait for a timeout when the queue is empty)
3. close the Blocking Connection.

Any help would be appreciated, thanks!