Commit cc3bdf8b authored by Pierre-Elliott Bécue's avatar Pierre-Elliott Bécue
Browse files

[cmb] Un message broker asynchrone pour RabbitMQ

 * Il n'y a que consumer pour l'instant, le producer viendra quand on
 en aura besoin
parent 84f389db
from consumer import AsynchronousConsumer
#!/bin/bash /usr/scripts/python.sh
# -*- coding: utf-8 -*-
#
# This code is a Crans production, based on pika documentation examples
# and on the RabbitMQ tutorials.
#
# This code is placed under the terms of GNU General Public License v3.
#
# Author : Pierre-Elliott Bécue <becue@crans.org>
# Date : 27/04/2014
# License : GPLv3
import sys
import pika
import cranslib.clogger as clogger
logger = clogger.CLogger(sys.argv[0].split("/")[-1].replace(".py", ""), "info")
class AsynchronousConsumer(object):
"""AsynchronousConsumer class
"""
def __init__(self, url, exchange_name, exchange_type):
"""Create a new instance of the asynchronous consumer.
"""
self._connection = None
self._channel = None
self._closing = False
self._consumer_tag = {}
self._queues = {}
self._exchange_name = exchange_name
self._exchange_type = exchange_type
self._url = url
#+--------------------------------+
#| Connection workers |
#+--------------------------------+
def connect(self):
"""Opens connection to the RabbitMQ server, and stores the connection
handle. Invokes the callback self.on_connection_open when things are
okay.
This callback will execute further operations.
"""
logger.info("Opening connection to RabbitMQ AMQP host %s…", self._url)
return pika.SelectConnection(pika.ConnectionParameters(self._url),
self.on_connection_open,
stop_ioloop_on_close=False
)
def on_connection_open(self, connection):
"""This method is called by pika once the connection to RabbitMQ has
been established. It passes the handle to the connection object in
case we need it.
Opens a channel when everything is ok.
:type connection: pika.SelectConnection
"""
logger.info('Connection to %s opened', self._url)
self.add_on_connection_close_callback()
self.open_channel()
def add_on_connection_close_callback(self):
"""This method adds an on close callback that will be invoked by pika
when RabbitMQ closes the connection to the publisher unexpectedly.
"""
logger.info('Adding connection close callback')
self._connection.add_on_close_callback(self.on_connection_closed)
def on_connection_closed(self, connection, reply_code, reply_text):
"""This method is invoked by pika when the connection to RabbitMQ is
closed unexpectedly. Since it is unexpected, we will reconnect to
RabbitMQ if it disconnects.
:param pika.connection.Connection connection: The closed connection obj
:param int reply_code: The server provided reply_code if given
:param str reply_text: The server provided reply_text if given
"""
self._channel = None
if self._closing:
self._connection.ioloop.stop()
else:
logger.warning('Connection closed, reopening in 5 seconds: (%s) %s',
reply_code, reply_text)
def reconnect(self):
"""Will be invoked by the IOLoop timer if the connection is
closed. See the on_connection_closed method.
"""
# This is the old connection IOLoop instance, stop its ioloop
self._connection.ioloop.stop()
if not self._closing:
# Create a new connection
self._connection = self.connect()
# There is now a new connection, needs a new ioloop to run
self._connection.ioloop.start()
def close_connection(self):
"""This method closes the connection to RabbitMQ."""
logger.info('Closing connection')
self._connection.close()
#+-------------------------------------+
#| Channel workspace |
#+-------------------------------------+
def open_channel(self):
"""Open a new channel with RabbitMQ by issuing the Channel.Open RPC
command. When RabbitMQ responds that the channel is open, the
on_channel_open callback will be invoked by pika.
"""
logger.info('Creating a new channel…')
self._connection.channel(on_open_callback=self.on_channel_open)
def on_channel_open(self, channel):
"""This method is invoked by pika when the channel has been opened.
The channel object is passed in so we can make use of it.
Since the channel is now open, we'll declare the exchange to use.
:param pika.channel.Channel channel: The channel object
"""
logger.info('Channel created.')
self._channel = channel
self.add_on_channel_close_callback()
self.setup_exchange(self._exchange_name, self._exchange_type)
def add_on_channel_close_callback(self):
"""This method tells pika to call the on_channel_closed method if
RabbitMQ unexpectedly closes the channel.
"""
logger.info('Adding channel close callback')
self._channel.add_on_close_callback(self.on_channel_closed)
def on_channel_closed(self, channel, reply_code, reply_text):
"""Invoked by pika when RabbitMQ unexpectedly closes the channel.
Channels are usually closed if you attempt to do something that
violates the protocol, such as re-declare an exchange or queue with
different parameters. In this case, we'll close the connection
to shutdown the object.
:param pika.channel.Channel: The closed channel
:param int reply_code: The numeric reason the channel was closed
:param str reply_text: The text reason the channel was closed
"""
logger.info("Channel %i was closed : (%s) %s",
channel, reply_code, reply_text)
logger.info('Channel was closed : (%s) %s',
reply_code, reply_text)
if not self._closing:
self.close_connection()
def close_channel(self):
"""Call to close the channel with RabbitMQ cleanly by issuing the
Channel.Close RPC command.
"""
logger.info('Closing the channel')
self._channel.close()
#+-------------------------------------+
#| Exchange methods |
#+-------------------------------------+
def setup_exchange(self, exchange_name, exchange_type):
"""Setup the exchange on RabbitMQ by invoking the Exchange.Declare RPC
command. When it is complete, the on_exchange_declareok method will
be invoked by pika.
:param str|unicode exchange_name: The name of the exchange to declare
"""
logger.info('Declaring exchange %s', exchange_name)
self._channel.exchange_declare(callback=self.on_exchange_declareok,
exchange=exchange_name,
exchange_type=exchange_type,
durable=True
)
def on_exchange_declareok(self, frame):
"""Invoked by pika when RabbitMQ has finished the Exchange.Declare RPC
command.
:param pika.Frame.Method frame: Exchange.DeclareOk response frame
"""
logger.info('Exchange declared')
self.setup_queues()
#+-------------------------------------+
#| Queue methods |
#+-------------------------------------+
def add_queue(self, queue_name, routing_key=''):
"""Add to self._queues the queue and the routing key
:param str|unicode queue_name: The name of the queue to add
:param str|unicode routing_key: The routing key associated
"""
self._queues[queue_name] = routing_key
def setup_queues(self):
"""Setup the queue on RabbitMQ by invoking the Queue.Declare RPC
command. When it is complete, the on_queue_declareok method will
be invoked by pika.
"""
for (queue_name, routing_key) in self._queues.items():
logger.info('Setting queue %s with routing key %s' % (queue_name, routing_key))
self._channel.queue_declare(
callback=self.on_queue_declareok,
queue=queue_name,
durable=True
)
def on_queue_declareok(self, method_frame):
"""Method invoked by pika when the Queue.Declare RPC call made in
setup_queues has completed. In this method we will bind the queue
and exchange together with the routing key by issuing the Queue.Bind
RPC command. When this command is complete, the on_bindok method will
be invoked by pika.
:param pika.frame.Method method_frame: The Queue.DeclareOk frame
"""
queue_name = method_frame.method.queue
routing_key = self._queues[queue_name]
logger.info('Binding %s to %s with %s',
self._exchange_name, queue_name, routing_key)
def on_bindok(frame):
"""Invoked by pika when the Queue.Bind method has completed. At this
point we will start consuming messages by calling start_consuming
which will invoke the needed RPC commands to start the process.
:param pika.frame.Method frame: The Queue.BindOk response frame
"""
logger.info('Queue %s bound.', queue_name)
self.start_consuming(queue_name)
self._channel.queue_bind(
callback=on_bindok,
queue=queue_name,
exchange=self._exchange_name,
routing_key=routing_key
)
def on_bindok(self, frame):
"""Invoked by pika when the Queue.Bind method has completed. At this
point we will start consuming messages by calling start_consuming
which will invoke the needed RPC commands to start the process.
:param pika.frame.Method frame: The Queue.BindOk response frame
"""
logger.info('Queue bound')
self.start_consuming(frame.method.queue)
#+-------------------------------------+
#| Cancel handle |
#+-------------------------------------+
def add_on_cancel_callback(self):
"""Add a callback that will be invoked if RabbitMQ cancels the consumer
for some reason. If RabbitMQ does cancel the consumer,
on_consumer_cancelled will be invoked by pika.
"""
logger.info('Adding consumer cancellation callback')
self._channel.add_on_cancel_callback(self.on_consumer_cancelled)
def on_consumer_cancelled(self, method_frame):
"""Invoked by pika when RabbitMQ sends a Basic.Cancel for a consumer
receiving messages.
:param pika.frame.Method method_frame: The Basic.Cancel frame
"""
logger.info('Consumer was cancelled remotely, shutting down: %r',
method_frame)
if self._channel:
self._channel.close()
def on_cancelok(self, frame):
"""This method is invoked by pika when RabbitMQ acknowledges the
cancellation of a consumer. At this point we will close the channel.
This will invoke the on_channel_closed method once the channel has been
closed, which will in-turn close the connection.
:param pika.frame.Method frame: The Basic.CancelOk frame
"""
logger.info('RabbitMQ acknowledged the cancellation of the consumer %s' %(frame.method.consumer_tag,))
self.close_channel()
#+-------------------------------------+
#| Message handling |
#+-------------------------------------+
def acknowledge_message(self, delivery_tag):
"""Acknowledge the message delivery from RabbitMQ by sending a
Basic.Ack RPC method for the delivery tag.
:param int delivery_tag: The delivery tag from the Basic.Deliver frame
"""
logger.info('Acknowledging message %s', delivery_tag)
self._channel.basic_ack(delivery_tag)
def on_message(self, channel, basic_deliver, properties, body):
"""Invoked by pika when a message is delivered from RabbitMQ. The
channel is passed for your convenience. The basic_deliver object that
is passed in carries the exchange, routing key, delivery tag and
a redelivered flag for the message. The properties passed in is an
instance of BasicProperties with the message properties and the body
is the message that was sent.
:param pika.channel.Channel channel: The channel object
:param pika.Spec.Basic.Deliver: basic_deliver method
:param pika.Spec.BasicProperties: properties
:param str|unicode body: The message body
"""
logger.info('Received message # %s from %s: %s',
basic_deliver.delivery_tag, properties.app_id, body)
self.acknowledge_message(basic_deliver.delivery_tag)
#+-------------------------------------+
#| Consumer handling |
#+-------------------------------------+
def stop_consuming(self, queue, tag):
"""Tell RabbitMQ that you would like to stop consuming by sending the
Basic.Cancel RPC command.
"""
if self._channel:
logger.info('Sending a Basic.Cancel RPC command to RabbitMQ for queue %s (tag : %s)' % (queue, tag,))
self._channel.basic_cancel(self.on_cancelok, tag)
def start_consuming(self, queue):
"""This method sets up the consumer by first calling
add_on_cancel_callback so that the object is notified if RabbitMQ
cancels the consumer. It then issues the Basic.Consume RPC command
which returns the consumer tag that is used to uniquely identify the
consumer with RabbitMQ. We keep the value to use it when we want to
cancel consuming. The on_message method is passed in as a callback pika
will invoke when a message is fully received.
"""
logger.info('Issuing consumer related RPC commands')
self.add_on_cancel_callback()
self._consumer_tag[queue] = self._channel.basic_consume(self.on_message,
queue)
def run(self):
"""Run the example consumer by connecting to RabbitMQ and then
starting the IOLoop to block and allow the SelectConnection to operate.
"""
logger.info("""Crans Message Broker
+--------------------------------------------+
| Welcome on CMB |
+--------------------------------------------+""")
self._connection = self.connect()
self.add_queue("test", "*.*.dhcp")
self._connection.ioloop.start()
def stop(self):
"""Cleanly shutdown the connection to RabbitMQ by stopping the consumer
with RabbitMQ. When RabbitMQ confirms the cancellation, on_cancelok
will be invoked by pika, which will then closing the channel and
connection. The IOLoop is started again because this method is invoked
when CTRL-C is pressed raising a KeyboardInterrupt exception. This
exception stops the IOLoop which needs to be running for pika to
communicate with RabbitMQ. All of the commands issued prior to starting
the IOLoop will be buffered but not processed.
"""
logger.info('Stopping')
self._closing = True
for (queue, tag) in self._consumer_tag.items():
self.stop_consuming(queue, tag)
self._consumer_tag.pop(queue)
self.close_channel()
self.close_connection()
logger.info('Stopped')
def main():
example = AsynchronousConsumer("civet.adm.crans.org", "exchange", "topic")
try:
example.run()
except KeyboardInterrupt:
logger.warning("Caught SIGINT, will now go for shutdown.")
example.stop()
if __name__ == '__main__':
main()
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