root / snf-common / synnefo / lib / amqp_puka.py @ 2ef10562
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# Copyright 2012 GRNET S.A. All rights reserved.
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#
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# Redistribution and use in source and binary forms, with or
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# without modification, are permitted provided that the following
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# conditions are met:
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#
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# 1. Redistributions of source code must retain the above
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# copyright notice, this list of conditions and the following
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# disclaimer.
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#
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# 2. Redistributions in binary form must reproduce the above
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# copyright notice, this list of conditions and the following
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# disclaimer in the documentation and/or other materials
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# provided with the distribution.
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#
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# THIS SOFTWARE IS PROVIDED BY GRNET S.A. ``AS IS'' AND ANY EXPRESS
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# OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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# WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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# PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL GRNET S.A OR
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# CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
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# USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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# AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
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# ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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# POSSIBILITY OF SUCH DAMAGE.
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#
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# The views and conclusions contained in the software and
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# documentation are those of the authors and should not be
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# interpreted as representing official policies, either expressed
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# or implied, of GRNET S.A.
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""" Module implementing connection and communication with an AMQP broker.
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AMQP Client's implemented by this module silenty detect connection failures and
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try to reconnect to any available broker. Also publishing takes advantage of
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publisher-confirms in order to guarantee that messages are properly delivered
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to the broker.
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"""
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import logging |
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from puka import Client |
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from puka import spec_exceptions |
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from socket import error as socket_error |
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from time import sleep |
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from random import shuffle |
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from functools import wraps |
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from ordereddict import OrderedDict |
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from synnefo import settings |
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logging.basicConfig(level=logging.DEBUG, |
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format="[%(levelname)s %(asctime)s] %(message)s")
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logger = logging.getLogger() |
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def reconnect_decorator(func): |
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"""
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Decorator for persistent connection with one or more AMQP brokers.
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"""
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@wraps(func)
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def wrapper(self, *args, **kwargs): |
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try:
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return func(self, *args, **kwargs) |
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except (socket_error, spec_exceptions.ConnectionForced) as e: |
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logger.error('Connection Closed while in %s: %s', func.__name__, e)
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self.consume_promises = []
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self.connect()
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return wrapper
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class AMQPPukaClient(object): |
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"""
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AMQP generic client implementing most of the basic AMQP operations.
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"""
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def __init__(self, hosts=settings.AMQP_HOSTS, max_retries=30, |
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confirms=True, confirm_buffer=100): |
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"""
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Format hosts as "amqp://username:pass@host:port"
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max_retries=0 defaults to unlimited retries
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"""
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self.hosts = hosts
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shuffle(self.hosts)
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self.max_retries = max_retries
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self.confirms = confirms
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self.confirm_buffer = confirm_buffer
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self.connection = None |
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self.channel = None |
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self.consumers = {}
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self.unacked = OrderedDict()
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self.unsend = OrderedDict()
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self.consume_promises = []
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self.exchanges = []
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def connect(self, retries=0): |
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if self.max_retries and retries >= self.max_retries: |
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logger.error("Aborting after %d retries", retries)
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raise AMQPConnectionError('Aborting after %d connection failures.'\ |
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% retries) |
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return
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# Pick up a host
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host = self.hosts.pop()
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self.hosts.insert(0, host) |
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self.client = Client(host, pubacks=self.confirms) |
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host = host.split('@')[-1] |
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logger.debug('Connecting to node %s' % host)
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try:
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promise = self.client.connect()
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self.client.wait(promise)
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except socket_error as e: |
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if retries < len(self.hosts): |
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logger.warning('Cannot connect to host %s: %s', host, e)
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else:
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logger.error('Cannot connect to host %s: %s', host, e)
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sleep(1)
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return self.connect(retries + 1) |
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logger.info('Successfully connected to host: %s', host)
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logger.info('Creating channel')
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if self.unacked: |
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self._resend_unacked_messages()
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if self.unsend: |
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self._resend_unsend_messages()
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if self.consumers: |
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for queue, callback in self.consumers.items(): |
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self.basic_consume(queue, callback)
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if self.exchanges: |
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exchanges = self.exchanges
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self.exchanges = []
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for exchange, type in exchanges: |
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self.exchange_declare(exchange, type) |
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def exchange_declare(self, exchange, type='direct'): |
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"""Declare an exchange
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@type exchange_name: string
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@param exchange_name: name of the exchange
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@type exchange_type: string
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@param exhange_type: one of 'direct', 'topic', 'fanout'
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"""
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logger.info('Declaring %s exchange: %s', type, exchange) |
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promise = self.client.exchange_declare(exchange=exchange,
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type=type,
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durable=True,
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auto_delete=False)
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self.client.wait(promise)
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self.exchanges.append((exchange, type)) |
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@reconnect_decorator
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def queue_declare(self, queue, exclusive=False, |
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mirrored=True, mirrored_nodes='all'): |
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"""Declare a queue
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@type queue: string
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@param queue: name of the queue
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@param mirrored: whether the queue will be mirrored to other brokers
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@param mirrored_nodes: the policy for the mirrored queue.
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Available policies:
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- 'all': The queue is mirrored to all nodes and the
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master node is the one to which the client is
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connected
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- a list of nodes. The queue will be mirrored only to
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the specified nodes, and the master will be the
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first node in the list. Node names must be provided
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and not host IP. example: [node1@rabbit,node2@rabbit]
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"""
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logger.info('Declaring queue: %s', queue)
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if mirrored:
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if mirrored_nodes == 'all': |
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arguments = {'x-ha-policy': 'all'} |
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elif isinstance(mirrored_nodes, list): |
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arguments = {'x-ha-policy': 'nodes', |
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'x-ha-policy-params': mirrored_nodes}
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else:
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raise AttributeError |
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else:
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arguments = {} |
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promise = self.client.queue_declare(queue=queue, durable=True, |
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exclusive=exclusive, |
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auto_delete=False,
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arguments=arguments) |
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self.client.wait(promise)
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def queue_bind(self, queue, exchange, routing_key): |
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logger.debug('Binding queue %s to exchange %s with key %s'
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% (queue, exchange, routing_key)) |
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promise = self.client.queue_bind(exchange=exchange, queue=queue,
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routing_key=routing_key) |
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self.client.wait(promise)
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@reconnect_decorator
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def basic_publish(self, exchange, routing_key, body): |
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"""Publish a message with a specific routing key """
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self._publish(exchange, routing_key, body)
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self.flush_buffer()
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if self.confirms and len(self.unacked) >= self.confirm_buffer: |
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self.get_confirms()
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@reconnect_decorator
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def basic_publish_multi(self, exchange, routing_key, bodies): |
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for body in bodies: |
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self.unsend[body] = (exchange, routing_key)
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for body in bodies: |
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self._publish(exchange, routing_key, body)
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self.unsend.pop(body)
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self.flush_buffer()
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if self.confirms: |
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self.get_confirms()
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def _publish(self, exchange, routing_key, body): |
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# Persisent messages by default!
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headers = {} |
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headers['delivery_mode'] = 2 |
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promise = self.client.basic_publish(exchange=exchange,
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routing_key=routing_key, |
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body=body, headers=headers) |
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if self.confirms: |
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self.unacked[promise] = (exchange, routing_key, body)
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return promise
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@reconnect_decorator
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def flush_buffer(self): |
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while self.client.needs_write(): |
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self.client.on_write()
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@reconnect_decorator
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def get_confirms(self): |
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for promise in self.unacked.keys(): |
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self.client.wait(promise)
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self.unacked.pop(promise)
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@reconnect_decorator
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def _resend_unacked_messages(self): |
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"""Resend unacked messages in case of a connection failure."""
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msgs = self.unacked.values()
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self.unacked.clear()
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for exchange, routing_key, body in msgs: |
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logger.debug('Resending message %s' % body)
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self.basic_publish(exchange, routing_key, body)
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@reconnect_decorator
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def _resend_unsend_messages(self): |
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"""Resend unsend messages in case of a connection failure."""
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for body in self.unsend.keys(): |
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(exchange, routing_key) = self.unsend[body]
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self.basic_publish(exchange, routing_key, body)
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self.unsend.pop(body)
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@reconnect_decorator
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def basic_consume(self, queue, callback, prefetch_count=0): |
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"""Consume from a queue.
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@type queue: string or list of strings
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@param queue: the name or list of names from the queues to consume
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@type callback: function
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@param callback: the callback function to run when a message arrives
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"""
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# Store the queues and the callback
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self.consumers[queue] = callback
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def handle_delivery(promise, msg): |
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"""Hide promises and messages without body"""
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if 'body' in msg: |
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callback(self, msg)
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else:
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logger.debug("Message without body %s" % msg)
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raise socket_error
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consume_promise = \ |
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self.client.basic_consume(queue=queue,
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prefetch_count=prefetch_count, |
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callback=handle_delivery) |
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self.consume_promises.append(consume_promise)
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return consume_promise
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@reconnect_decorator
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def basic_wait(self, promise=None, timeout=0): |
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"""Wait for messages from the queues declared by basic_consume.
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This function will block until a message arrives from the queues that
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have been declared with basic_consume. If the optional arguments
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'promise' is given, only messages for this promise will be delivered.
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"""
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if promise is not None: |
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self.client.wait(promise, timeout)
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else:
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self.client.wait(self.consume_promises) |
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@reconnect_decorator
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def basic_get(self, queue): |
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"""Get a single message from a queue.
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This is a non-blocking method for getting messages from a queue.
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It will return None if the queue is empty.
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"""
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get_promise = self.client.basic_get(queue=queue)
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result = self.client.wait(get_promise)
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if 'empty' in result: |
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# The queue is empty
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return None |
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else:
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return result
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@reconnect_decorator
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def basic_ack(self, message): |
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self.client.basic_ack(message)
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@reconnect_decorator
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def basic_nack(self, message): |
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#TODO:
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pass
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def close(self): |
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"""Check that messages have been send and close the connection."""
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try:
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if self.confirms: |
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self.get_confirms()
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close_promise = self.client.close()
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self.client.wait(close_promise)
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except (socket_error, spec_exceptions.ConnectionForced) as e: |
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logger.error('Connection closed while closing connection:%s',
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e) |
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def queue_delete(self, queue, if_unused=True, if_empty=True): |
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"""Delete a queue.
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Returns False if the queue does not exist
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"""
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try:
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promise = self.client.queue_delete(queue=queue,
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if_unused=if_unused, |
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if_empty=if_empty) |
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self.client.wait(promise)
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return True |
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except spec_exceptions.NotFound:
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logger.info("Queue %s does not exist", queue)
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return False |
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def exchange_delete(self, exchange, if_unused=True): |
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"""Delete an exchange."""
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try:
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promise = self.client.exchange_delete(exchange=exchange,
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if_unused=if_unused) |
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self.client.wait(promise)
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return True |
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except spec_exceptions.NotFound:
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logger.info("Exchange %s does not exist", exchange)
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return False |
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@reconnect_decorator
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def basic_cancel(self, promise=None): |
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"""Cancel consuming from a queue. """
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if promise is not None: |
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self.client.basic_cancel(promise)
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else:
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for promise in self.consume_promises: |
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self.client.basic_cancel(promise)
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class AMQPConnectionError(Exception): |
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pass
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