[rabbitmq-discuss] Problem extending code from tutorial #6

Wed Aug 24 02:49:51 BST 2011

I'm hoping someone can help he with my RabbitMQ problem; I've got some
code based on the tutorial #6 code, and it's not doing what I'm expecting.
I tried to create a shell where I can send strings to the server and
receive the MD5 digest, but I only ever seem to get the first reply.

Here's the source:

##########################################################################
# server.py

import pika
import hashlib

connection = pika.BlockingConnection(
    pika.ConnectionParameters(host='localhost'))

channel = connection.channel()
channel.queue_declare(queue='my_request')

def on_request(ch, method, props, body):

    response = hashlib.md5(body).hexdigest()

    print("Received '%r', sending '%r'" % (body, response))

    ch.basic_publish(exchange='',
                     routing_key=props.reply_to,
                     properties=pika.BasicProperties(correlation_id = \
                                                     props.correlation_id),
                     body=response)

    ch.basic_ack(delivery_tag = method.delivery_tag)

channel.basic_qos(prefetch_count=1)
channel.basic_consume(on_request, queue='my_request')

print " [x] Awaiting requests"
channel.start_consuming()
##########################################################################

##########################################################################
# client.py

import pika
import uuid

class RabbitClient(object):

    def __init__(self):
        self.connection = pika.BlockingConnection(
            pika.ConnectionParameters(host='localhost'))

        self.channel = self.connection.channel()

        result = self.channel.queue_declare(exclusive=True)
        self.callback_queue = result.method.queue

        self.channel.basic_consume(self.on_response, no_ack=True,
                                   queue=self.callback_queue)

    def on_response(self, ch, method, props, body):
        print(" [.] Received correlation ID %r" % (props.correlation_id,))
        if self.corr_id == props.correlation_id:
            self.response = body
            self.channel.stop_consuming()
        else:
            print(" [~] Correlation IDs do not match")

    def call(self, n):
        self.corr_id = str(uuid.uuid4())
        self.channel.basic_publish(exchange='',
                                   routing_key='my_request',
                                   properties=pika.BasicProperties(
                                         reply_to=self.callback_queue,
                                         correlation_id=self.corr_id,
                                         ),
                                   body=n)
        self.channel.start_consuming()
        return self.response

auth = RabbitClient()

while True:
    send = raw_input('> ')
    if send == 'quit': break
    print(" [x] sending '%s'" % (send))
    response = auth.call(send)
    print(" [^] sent with correlation ID %s" % (auth.corr_id,))
    print(" [.] Got %r" % (response,))
##########################################################################

Here's the output from the server:

##########################################################################
 [x] Awaiting requests
Received ''Hello World'', sending ''b10a8db164e0754105b7a99be72e3fe5''
Received ''Hello Rabbit'', sending ''5bec01f45b43f6202e84242fcb71b04f''
##########################################################################

And here's the output from the server:
##########################################################################
> Hello World
 [x] sending 'Hello World'
 [.] Received correlation ID '1805f131-1fbc-40a3-86fb-2a113b5f9b9a'
 [^] sent with correlation ID 1805f131-1fbc-40a3-86fb-2a113b5f9b9a
 [.] Got 'b10a8db164e0754105b7a99be72e3fe5'
> Hello Rabbit
 [x] sending 'Hello Rabbit'
 [^] sent with correlation ID fdb089ff-44ea-4b81-885b-be7e0178d5a1
 [.] Got 'b10a8db164e0754105b7a99be72e3fe5'
> quit
##########################################################################

So, my question is, what am I doing wrong that I didn't get the '5bec'
response to the second message?

Thanks for your help,
-- 
Doug Gorley | doug at gorley.ca