Subscription with selector does not work from python - stomp.py

Question

I have run into a problem where a Python subscriber using stomp (stomp.py) with a message selector does not receive the messages it should. Interestingly enough, it appears to me at least that the problem is somehow with the sending of the message and not the subscription.

I am using ActiveMQ.

Here's the subscriber code:

class Listener(object):

    def __init__(self, count):
        if count <= 0:
            count = float('inf')
        self.count = count

    def on_error(self, headers, message):
        print("=" * 72)
        print('RECEIVED AN ERROR.')
        print('Message headers:')
        pp = pprint.PrettyPrinter(indent=4)
        pp.pprint(headers)
        print('Message body:')
        print(message)

    def on_message(self, headers, message):
        print("=" * 72)
        print('Message headers:')
        pp = pprint.PrettyPrinter(indent=4)
        pp.pprint(headers)
        print('Message body:')
        print(message)

def main():
    global conn

    args = parse_args()
    conn = stomp.Connection([(args.host, args.port)])
    conn.set_listener('Listener', Listener(args.count))
    conn.start()
    conn.connect(login=args.user, passcode=args.password)

    if (args.selector):
        conn.subscribe(
            destination=args.destination,
            id=1,
            ack='auto',
            headers={'selector': args.selector}
        )
    else:
        conn.subscribe(
            destination=args.destination,
            id=1,
            ack='auto'
        )

Now I can run this subscriber with a selector such as "type = 'test'".

If I publish a message using Java JMS, the message is received just fine. However, if I publish the identical message from Python it is not.

Here's the relevant Python publishing code:

headers = {}
headers['type'] = 'test'

conn = stomp.Connection12([(args.host, args.port)], auto_content_length=False)
conn.start()
conn.connect(login=args.user, passcode=args.password)
conn.send(body=body, headers=headers, destination=args.destination)
conn.disconnect()
print 'Message sent.'

Some interesting notes from my testing and debugging:

1. Running the subscriber with a selector receives a matching message sent from Java JMS but not from Python.
2. Running the subscriber with no selector receives a message sent from Java and also a message sent from Python.

Answer 1

fairly old, but I was currently facing the same issue and so I would like to leave a possible solution here.

At first, according to the documentation, you can provide a field called selectorwith SQL like syntax and should be part of the headers. In your example:

headers = {}
headers['selector'] = "type='test'"
conn = stomp.Connection12([(args.host, args.port)], auto_content_length=False)
conn.start()
conn.connect(login=args.user, passcode=args.password)
conn.send(body=body, headers=headers, destination=args.destination)
conn.disconnect()
print 'Message sent.'

I was also facing the error, that I could not receive any message send from JMS, but after a lot of reading, I found here, that there is a field name JMSType. I changed the code to

headers['selector'] = "type='test' OR JMSType='test'"

With that JMSType in there everything works like expected. Hope that helps somebody