Pika basic_publish hangs when publishing on multiple queues

Question

I need to setup multiple queues on an exchange. I would like to create a single connection, then declare multiple queues (this works) then, publish messages on the multiple queues (this does not work).

I setup some test code to do this, but it gets hung up on the 2nd publish everytime. I think it does not like publishing on multiple queues without closing the connection, as this code works when I publish on a single queue (even multiple messages on a single queue).

Is there something I need to add to make this work? I would really like to not have to close the connection between publishes. Also, when I have my consumers up, they do not see anything when I send to basic_publish()'s when sending on multiple queues. I do see messages appear almost instantly when I am publishing on a single queue.

#!/usr/bin/env python
import pika


queue_names = ['1a', '2b', '3c', '4d']


# Variables to hold our connection and channel
connection = None
channel = None


# Called when our connection to RabbitMQ is closed
def on_closed(frame):
    global connection
    # connection.ioloop is blocking, this will stop and exit the app
    connection.ioloop.stop()



def on_connected(connection):
    """
    Called when we have connected to RabbitMQ
    This creates a channel on the connection
    """
    global channel #TODO: Test removing this global call

    connection.add_on_close_callback(on_closed)

    # Create a channel on our connection passing the on_channel_open callback
    connection.channel(on_channel_open)



def on_channel_open(channel_):
    """
    Called when channel opened
    Declare a queue on the channel
    """
    global channel

    # Our usable channel has been passed to us, assign it for future use
    channel = channel_


    # Declare a set of queues on this channel
    for queue_name in reversed(queue_names):
        channel.queue_declare(queue=queue_name, durable=True,
                              exclusive=False, auto_delete=False,
                              callback=on_queue_declared)
        #print "done making hash"

def on_queue_declared(frame):
    """
    Called when a queue is declared
    """
    global channel

    print "Sending 'Hello World!' on ", frame.method.queue

    # Send a message
    channel.basic_publish(exchange='',
                          routing_key=frame.method.queue,
                          body='Hello World!')


# Create our connection parameters and connect to RabbitMQ
connection = pika.SelectConnection(pika.ConnectionParameters('localhost'), \
                                   on_connected)

# Start our IO/Event loop
try:
    connection.ioloop.start()
except KeyboardInterrupt:
    print "interrupt"
    # Gracefully close the connection
    connection.close()
    # Loop until we're fully closed, will stop on its own
    #connection.ioloop.start()

Answer 1

My solution to this was to have a variable keep track of whether all my queues were declared or not.

In on_queue_declared(), I would check this variable and, if all my queues were declared, then I start publishing messages. I believe attempting to publish messages before getting back all the Queue.DeclareOks was causing the issues.