A very simple way to interact with python amqplib

flopsy.py

"""
Copyright (c) 2008-2009, Nathan Borror
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SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

Flopsy
======

A very simple way to interact with python AMQPlib. For my case I'm using
RabbitMQ as my implementation but it should work with others.

settings.py
-----------

AMQP_SERVER = '24.143.38.241'
AMQP_PORT = 5672
AMQP_USER = 'guest'
AMQP_PASSWORD = 'guest'
AMQP_VHOST = '/'

Consumer
--------

>>> from flopsy import Connection, Consumer
>>> consumer = Consumer(connection=Connection())
>>> consumer.declare(queue='po_box', exchange='sorting_room', routing_key='jason', auto_delete=False)

>>> def message_callback(message):
...     print 'Recieved: ' + message.body
...     consumer.channel.basic_ack(message.delivery_tag)
>>>
>>> consumer.register(message_callback)
>>> consumer.wait()

Publisher
---------

>>> from flopsy import Connection, Publisher
>>> publisher = Publisher(connection=Connection(), exchange='sorting_room', routing_key='jason')
>>> publisher.publish('Test message!')
>>> publisher.close()
"""


from django.conf import settings
from amqplib import client_0_8 as amqp


class Connection(object):
    def __init__(self, *args, **kwargs):

        self.host = kwargs.get('host', getattr(settings, 'AMQP_SERVER'))
        self.user_id = kwargs.get('user_id', getattr(settings, 'AMQP_USER'))
        self.password = kwargs.get('password', getattr(settings, 'AMQP_PASSWORD'))
        self.vhost = kwargs.get('vhost', getattr(settings, 'AMQP_VHOST', '/'))
        self.port = kwargs.get('port', getattr(settings, 'AMQP_PORT', 5672))
        self.insist = False

        self.connect()

    def connect(self):
        self.connection = amqp.Connection(host='%s:%s' % (self.host, self.port), userid=self.user_id,
                password=self.password, virtual_host=self.vhost, insist=self.insist)


class Consumer(object):
    def __init__(self, connection):
        self.connection = connection
        self.channel = self.connection.connection.channel()

    def close(self):
        if getattr(self, 'channel'):
            self.channel.close()
        if getattr(self, 'connection'):
            self.connection.close()

    def declare(self, queue, exchange, routing_key, durable=True, exclusive=False, auto_delete=False):
        self.queue = queue
        self.exchange = exchange
        self.routing_key = routing_key

        self.channel.queue_declare(queue=self.queue, durable=durable,
                exclusive=exclusive, auto_delete=auto_delete)
        self.channel.exchange_declare(exchange=self.exchange, type='direct',
                durable=durable, auto_delete=auto_delete)
        self.channel.queue_bind(queue=self.queue, exchange=self.exchange,
                routing_key=self.routing_key)

    def wait(self):
        while True:
            self.channel.wait()

    def register(self, callback, queue=None, consumer_tag='flopsy_callback'):
        if hasattr(self, 'queue') or queue:
            self.consumer_tag = consumer_tag
            self.channel.basic_consume(queue=getattr(self, 'queue', queue), no_ack=True, 
                callback=callback, consumer_tag=consumer_tag)

    def unregister(self, consumer_tag='flopsy_callback'):
        self.channel.basic_cancel(consumer_tag)


class Publisher(object):
    def __init__(self, connection, exchange, routing_key, delivery_mode=2):
        self.connection = connection
        self.channel = self.connection.connection.channel()
        self.exchange = exchange
        self.routing_key = routing_key
        self.delivery_mode = delivery_mode

    def publish(self, message_data):
        message = amqp.Message(message_data)
        message.properties['delivery_mode'] = self.delivery_mode
        self.channel.basic_publish(message, exchange=self.exchange, routing_key=self.routing_key)
        return message

    def close(self):
        if getattr(self, 'channel'):
            self.channel.close()
        if getattr(self, 'connection'):
            self.connection.connection.close()

I'm wondering whether there's a way to wait for a single message with flopsy, without mucking with the underlying amqplib code. consumer.wait() seems to go into an infinite loop that can't be broken; is that right? Is there a way to just check for messages periodically?