Hello World using ‘kombu’ library and python

2013/09/30
16:32

Development, Models and Methodologies, System administration, Databases, Messaging and Security, Technology

Reading time: 62 – 103 minutes

Some times schemas and snippets don’t need large descriptions. If you think this is not enough in this case tell me and I’m going to add explanations.

Using a python library called kombu as an abstraction to talk with AMQP broker we are going to develop different message routes setting each type of Exchange. As a backend I used RabbitMQ with default configuration.

AMQP schema using an exchange of type direct

Queue definition:

from kombu import Exchange, Queue

task_exchange = Exchange("msgs", type="direct")
queue_msg_1 = Queue("messages_1", task_exchange, routing_key = 'message_1')
queue_msg_2 = Queue("messages_2", task_exchange, routing_key = 'message_2')

The producer:

from __future__ import with_statement
from queues import task_exchange

from kombu.common import maybe_declare
from kombu.pools import producers


if __name__ == "__main__":
    from kombu import BrokerConnection

    connection = BrokerConnection("amqp://guest:guest@localhost:5672//")

    with producers[connection].acquire(block=True) as producer:
        maybe_declare(task_exchange, producer.channel)
        
        payload = {"type": "handshake", "content": "hello #1"}
        producer.publish(payload, exchange = 'msgs', serializer="pickle", routing_key = 'message_1')
        
        payload = {"type": "handshake", "content": "hello #2"}
        producer.publish(payload, exchange = 'msgs', serializer="pickle", routing_key = 'message_2')

One consumer:

from queues import queue_msg_1
from kombu.mixins import ConsumerMixin

class C(ConsumerMixin):
    def __init__(self, connection):
        self.connection = connection
        return
    
    def get_consumers(self, Consumer, channel):
        return [Consumer( queue_msg_1, callbacks = [ self.on_message ])]
    
    def on_message(self, body, message):
        print ("RECEIVED MSG - body: %r" % (body,))
        print ("RECEIVED MSG - message: %r" % (message,))
        message.ack()
        return
    

if __name__ == "__main__":
    from kombu import BrokerConnection
    from kombu.utils.debug import setup_logging
    
    setup_logging(loglevel="DEBUG")

    with BrokerConnection("amqp://guest:guest@localhost:5672//") as connection:
        try:
            C(connection).run()
        except KeyboardInterrupt:
            print("bye bye")

AMQP schema using an exchange of type fanout

Queue definition:

from kombu import Exchange, Queue

task_exchange = Exchange("ce", type="fanout")
queue_events_db = Queue("events.db", task_exchange)
queue_events_notify = Queue("events.notify", task_exchange)

The producer:

from __future__ import with_statement
from queues import task_exchange

from kombu.common import maybe_declare
from kombu.pools import producers


if __name__ == "__main__":
    from kombu import BrokerConnection

    connection = BrokerConnection("amqp://guest:guest@localhost:5672//")

    with producers[connection].acquire(block=True) as producer:
        maybe_declare(task_exchange, producer.channel)
        
        payload = {"operation": "create", "content": "the object"}
        producer.publish(payload, exchange = 'ce', serializer="pickle", routing_key = 'user.write')

        payload = {"operation": "update", "content": "updated fields", "id": "id of the object"}
        producer.publish(payload, exchange = 'ce', serializer="pickle", routing_key = 'user.write')

One consumer:

from queues import queue_events_db
from kombu.mixins import ConsumerMixin

class C(ConsumerMixin):
    def __init__(self, connection):
        self.connection = connection
        return
    
    def get_consumers(self, Consumer, channel):
        return [Consumer( queue_events_db, callbacks = [self.on_message])]
    
    def on_message(self, body, message):
        print ("save_db: RECEIVED MSG - body: %r" % (body,))
        print ("save_db: RECEIVED MSG - message: %r" % (message,))
        message.ack()
        return


if __name__ == "__main__":
    from kombu import BrokerConnection
    from kombu.utils.debug import setup_logging
    
    setup_logging(loglevel="DEBUG")

    with BrokerConnection("amqp://guest:guest@localhost:5672//") as connection:
        try:
            C(connection).run()
        except KeyboardInterrupt:
            print("bye bye")

AMQP schema using an exchange of type topic

Queue definition:

from kombu import Exchange, Queue

task_exchange = Exchange("user", type="topic")
queue_user_write = Queue("user.write", task_exchange, routing_key = 'user.write')
queue_user_read = Queue("user.read", task_exchange, routing_key = 'user.read')
queue_notify = Queue("notify", task_exchange, routing_key = 'user.#')

The producer:

from __future__ import with_statement
from queues import task_exchange

from kombu.common import maybe_declare
from kombu.pools import producers


if __name__ == "__main__":
    from kombu import BrokerConnection

    connection = BrokerConnection("amqp://guest:guest@localhost:5672//")

    with producers[connection].acquire(block=True) as producer:
        maybe_declare(task_exchange, producer.channel)
        
        payload = {"operation": "create", "content": "the object"}
        producer.publish(payload, exchange = 'user', serializer="pickle", routing_key = 'user.write')

        payload = {"operation": "update", "content": "updated fields", "id": "id of the object"}
        producer.publish(payload, exchange = 'user', serializer="pickle", routing_key = 'user.write')

        payload = {"operation": "delete", "id": "id of the object"}
        producer.publish(payload, exchange = 'user', serializer="pickle", routing_key = 'user.write')

        payload = {"operation": "read", "id": "id of the object"}
        producer.publish(payload, exchange = 'user', serializer="pickle", routing_key = 'user.read')

One consumer:

from queues import queue_events_db
from kombu.mixins import ConsumerMixin

class C(ConsumerMixin):
    def __init__(self, connection):
        self.connection = connection
        return
    
    def get_consumers(self, Consumer, channel):
        return [Consumer( queue_events_db, callbacks = [self.on_message])]
    
    def on_message(self, body, message):
        print ("save_db: RECEIVED MSG - body: %r" % (body,))
        print ("save_db: RECEIVED MSG - message: %r" % (message,))
        message.ack()
        return


if __name__ == "__main__":
    from kombu import BrokerConnection
    from kombu.utils.debug import setup_logging
    
    setup_logging(loglevel="DEBUG")

    with BrokerConnection("amqp://guest:guest@localhost:5672//") as connection:
        try:
            C(connection).run()
        except KeyboardInterrupt:
            print("bye bye")

Simple queues

Kombu implements SimpleQueue and SimpleBuffer as simple solution for queues with exchange of type ‘direct’, with the same exchange name, routing key and queue name.

Pusher:

from kombu import BrokerConnection

connection = BrokerConnection("amqp://guest:guest@localhost:5672//")
queue = connection.SimpleQueue("logs")

payload = { "severity":"info", "message":"this is just a log", "ts":"2013/09/30T15:10:23" }
queue.put(payload, serializer='pickle')

queue.close()

Getter:

from kombu import BrokerConnection
from Queue import  Empty

connection = BrokerConnection("amqp://guest:guest@localhost:5672//")

queue = connection.SimpleQueue("logs")

while 1:
    try:
        message = queue.get(block=True, timeout=1)
        print message.payload
        message.ack()
    except Empty:
        pass
    except KeyboardInterrupt:
        break
    print message

queue.close()

The files

Download all example files: kombu-tests.tar.gz

5 thoughts on “Hello World using ‘kombu’ library and python”

Richard Loo
2013/10/14 at 23:42

thanks for sharing, great post.

I have one question, what is “maybe_declare” used for?
Oriol Rius
2013/10/15 at 06:49

It’s used to create, if it’s necessary, the entities of RabbitMQ: exchange, binding and queues. If the entities was created before it does nothing.
Anuj
2014/01/17 at 10:53

I know this question does not make sense..But can I extend this to run on Django Web Server and create an IOS app that use API to send and receive message, more like chat application ?
Germán Larraín
2014/07/09 at 16:14

It’s like “create if it does not exist”
gamesbook
2015/01/19 at 16:14

Rather look to use Django REST API and a tool such SwampDragon.

Comments are closed.