394 lines
14 KiB
Python
394 lines
14 KiB
Python
# vim: tabstop=4 shiftwidth=4 softtabstop=4
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# Copyright 2010 United States Government as represented by the
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# Administrator of the National Aeronautics and Space Administration.
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# All Rights Reserved.
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#
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# Licensed under the Apache License, Version 2.0 (the "License"); you may
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# not use this file except in compliance with the License. You may obtain
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# a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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# License for the specific language governing permissions and limitations
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# under the License.
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"""
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AMQP-based RPC. Queues have consumers and publishers.
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No fan-out support yet.
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"""
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import json
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import sys
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import time
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import traceback
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import uuid
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from carrot import connection as carrot_connection
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from carrot import messaging
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from eventlet import greenthread
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from nova import context
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from nova import exception
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from nova import fakerabbit
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from nova import flags
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from nova import log as logging
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from nova import utils
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FLAGS = flags.FLAGS
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LOG = logging.getLogger('nova.rpc')
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class Connection(carrot_connection.BrokerConnection):
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"""Connection instance object"""
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@classmethod
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def instance(cls, new=False):
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"""Returns the instance"""
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if new or not hasattr(cls, '_instance'):
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params = dict(hostname=FLAGS.rabbit_host,
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port=FLAGS.rabbit_port,
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userid=FLAGS.rabbit_userid,
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password=FLAGS.rabbit_password,
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virtual_host=FLAGS.rabbit_virtual_host)
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if FLAGS.fake_rabbit:
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params['backend_cls'] = fakerabbit.Backend
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# NOTE(vish): magic is fun!
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# pylint: disable-msg=W0142
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if new:
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return cls(**params)
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else:
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cls._instance = cls(**params)
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return cls._instance
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@classmethod
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def recreate(cls):
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"""Recreates the connection instance
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This is necessary to recover from some network errors/disconnects"""
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del cls._instance
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return cls.instance()
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class Consumer(messaging.Consumer):
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"""Consumer base class
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Contains methods for connecting the fetch method to async loops
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"""
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def __init__(self, *args, **kwargs):
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for i in xrange(FLAGS.rabbit_max_retries):
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if i > 0:
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time.sleep(FLAGS.rabbit_retry_interval)
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try:
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super(Consumer, self).__init__(*args, **kwargs)
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self.failed_connection = False
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break
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except: # Catching all because carrot sucks
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LOG.exception(_("AMQP server on %s:%d is unreachable."
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" Trying again in %d seconds.") % (
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FLAGS.rabbit_host,
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FLAGS.rabbit_port,
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FLAGS.rabbit_retry_interval))
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self.failed_connection = True
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if self.failed_connection:
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LOG.exception(_("Unable to connect to AMQP server "
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"after %d tries. Shutting down."),
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FLAGS.rabbit_max_retries)
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sys.exit(1)
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def fetch(self, no_ack=None, auto_ack=None, enable_callbacks=False):
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"""Wraps the parent fetch with some logic for failed connections"""
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# TODO(vish): the logic for failed connections and logging should be
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# refactored into some sort of connection manager object
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try:
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if self.failed_connection:
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# NOTE(vish): connection is defined in the parent class, we can
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# recreate it as long as we create the backend too
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# pylint: disable-msg=W0201
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self.connection = Connection.recreate()
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self.backend = self.connection.create_backend()
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self.declare()
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super(Consumer, self).fetch(no_ack, auto_ack, enable_callbacks)
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if self.failed_connection:
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LOG.error(_("Reconnected to queue"))
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self.failed_connection = False
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# NOTE(vish): This is catching all errors because we really don't
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# exceptions to be logged 10 times a second if some
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# persistent failure occurs.
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except Exception: # pylint: disable-msg=W0703
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if not self.failed_connection:
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LOG.exception(_("Failed to fetch message from queue"))
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self.failed_connection = True
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def attach_to_eventlet(self):
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"""Only needed for unit tests!"""
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timer = utils.LoopingCall(self.fetch, enable_callbacks=True)
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timer.start(0.1)
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return timer
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class Publisher(messaging.Publisher):
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"""Publisher base class"""
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pass
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class TopicConsumer(Consumer):
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"""Consumes messages on a specific topic"""
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exchange_type = "topic"
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def __init__(self, connection=None, topic="broadcast"):
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self.queue = topic
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self.routing_key = topic
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self.exchange = FLAGS.control_exchange
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self.durable = False
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super(TopicConsumer, self).__init__(connection=connection)
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class AdapterConsumer(TopicConsumer):
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"""Calls methods on a proxy object based on method and args"""
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def __init__(self, connection=None, topic="broadcast", proxy=None):
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LOG.debug(_('Initing the Adapter Consumer for %s') % (topic))
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self.proxy = proxy
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super(AdapterConsumer, self).__init__(connection=connection,
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topic=topic)
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@exception.wrap_exception
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def receive(self, message_data, message):
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"""Magically looks for a method on the proxy object and calls it
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Message data should be a dictionary with two keys:
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method: string representing the method to call
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args: dictionary of arg: value
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Example: {'method': 'echo', 'args': {'value': 42}}
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"""
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LOG.debug(_('received %s') % (message_data))
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msg_id = message_data.pop('_msg_id', None)
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ctxt = _unpack_context(message_data)
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method = message_data.get('method')
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args = message_data.get('args', {})
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message.ack()
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if not method:
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# NOTE(vish): we may not want to ack here, but that means that bad
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# messages stay in the queue indefinitely, so for now
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# we just log the message and send an error string
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# back to the caller
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LOG.warn(_('no method for message: %s') % (message_data))
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msg_reply(msg_id, _('No method for message: %s') % message_data)
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return
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node_func = getattr(self.proxy, str(method))
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node_args = dict((str(k), v) for k, v in args.iteritems())
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# NOTE(vish): magic is fun!
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try:
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rval = node_func(context=ctxt, **node_args)
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if msg_id:
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msg_reply(msg_id, rval, None)
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except Exception as e:
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logging.exception("Exception during message handling")
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if msg_id:
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msg_reply(msg_id, None, sys.exc_info())
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return
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class TopicPublisher(Publisher):
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"""Publishes messages on a specific topic"""
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exchange_type = "topic"
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def __init__(self, connection=None, topic="broadcast"):
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self.routing_key = topic
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self.exchange = FLAGS.control_exchange
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self.durable = False
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super(TopicPublisher, self).__init__(connection=connection)
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class DirectConsumer(Consumer):
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"""Consumes messages directly on a channel specified by msg_id"""
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exchange_type = "direct"
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def __init__(self, connection=None, msg_id=None):
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self.queue = msg_id
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self.routing_key = msg_id
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self.exchange = msg_id
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self.auto_delete = True
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self.exclusive = True
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super(DirectConsumer, self).__init__(connection=connection)
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class DirectPublisher(Publisher):
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"""Publishes messages directly on a channel specified by msg_id"""
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exchange_type = "direct"
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def __init__(self, connection=None, msg_id=None):
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self.routing_key = msg_id
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self.exchange = msg_id
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self.auto_delete = True
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super(DirectPublisher, self).__init__(connection=connection)
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def msg_reply(msg_id, reply=None, failure=None):
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"""Sends a reply or an error on the channel signified by msg_id
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failure should be a sys.exc_info() tuple.
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"""
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if failure:
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message = str(failure[1])
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tb = traceback.format_exception(*failure)
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LOG.error(_("Returning exception %s to caller"), message)
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LOG.error(tb)
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failure = (failure[0].__name__, str(failure[1]), tb)
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conn = Connection.instance(True)
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publisher = DirectPublisher(connection=conn, msg_id=msg_id)
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try:
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publisher.send({'result': reply, 'failure': failure})
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except TypeError:
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publisher.send(
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{'result': dict((k, repr(v))
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for k, v in reply.__dict__.iteritems()),
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'failure': failure})
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publisher.close()
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class RemoteError(exception.Error):
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"""Signifies that a remote class has raised an exception
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Containes a string representation of the type of the original exception,
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the value of the original exception, and the traceback. These are
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sent to the parent as a joined string so printing the exception
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contains all of the relevent info."""
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def __init__(self, exc_type, value, traceback):
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self.exc_type = exc_type
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self.value = value
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self.traceback = traceback
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super(RemoteError, self).__init__("%s %s\n%s" % (exc_type,
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value,
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traceback))
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def _unpack_context(msg):
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"""Unpack context from msg."""
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context_dict = {}
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for key in list(msg.keys()):
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# NOTE(vish): Some versions of python don't like unicode keys
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# in kwargs.
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key = str(key)
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if key.startswith('_context_'):
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value = msg.pop(key)
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context_dict[key[9:]] = value
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LOG.debug(_('unpacked context: %s'), context_dict)
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return context.RequestContext.from_dict(context_dict)
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def _pack_context(msg, context):
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"""Pack context into msg.
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Values for message keys need to be less than 255 chars, so we pull
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context out into a bunch of separate keys. If we want to support
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more arguments in rabbit messages, we may want to do the same
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for args at some point.
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"""
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context = dict([('_context_%s' % key, value)
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for (key, value) in context.to_dict().iteritems()])
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msg.update(context)
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def call(context, topic, msg):
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"""Sends a message on a topic and wait for a response"""
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LOG.debug(_("Making asynchronous call..."))
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msg_id = uuid.uuid4().hex
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msg.update({'_msg_id': msg_id})
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LOG.debug(_("MSG_ID is %s") % (msg_id))
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_pack_context(msg, context)
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class WaitMessage(object):
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def __call__(self, data, message):
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"""Acks message and sets result."""
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message.ack()
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if data['failure']:
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self.result = RemoteError(*data['failure'])
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else:
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self.result = data['result']
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wait_msg = WaitMessage()
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conn = Connection.instance(True)
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consumer = DirectConsumer(connection=conn, msg_id=msg_id)
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consumer.register_callback(wait_msg)
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conn = Connection.instance()
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publisher = TopicPublisher(connection=conn, topic=topic)
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publisher.send(msg)
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publisher.close()
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try:
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consumer.wait(limit=1)
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except StopIteration:
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pass
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consumer.close()
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# NOTE(termie): this is a little bit of a change from the original
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# non-eventlet code where returning a Failure
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# instance from a deferred call is very similar to
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# raising an exception
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if isinstance(wait_msg.result, Exception):
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raise wait_msg.result
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return wait_msg.result
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def cast(context, topic, msg):
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"""Sends a message on a topic without waiting for a response"""
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LOG.debug("Making asynchronous cast...")
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_pack_context(msg, context)
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conn = Connection.instance()
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publisher = TopicPublisher(connection=conn, topic=topic)
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publisher.send(msg)
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publisher.close()
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def generic_response(message_data, message):
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"""Logs a result and exits"""
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LOG.debug(_('response %s'), message_data)
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message.ack()
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sys.exit(0)
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def send_message(topic, message, wait=True):
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"""Sends a message for testing"""
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msg_id = uuid.uuid4().hex
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message.update({'_msg_id': msg_id})
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LOG.debug(_('topic is %s'), topic)
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LOG.debug(_('message %s'), message)
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if wait:
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consumer = messaging.Consumer(connection=Connection.instance(),
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queue=msg_id,
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exchange=msg_id,
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auto_delete=True,
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exchange_type="direct",
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routing_key=msg_id)
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consumer.register_callback(generic_response)
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publisher = messaging.Publisher(connection=Connection.instance(),
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exchange=FLAGS.control_exchange,
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durable=False,
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exchange_type="topic",
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routing_key=topic)
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publisher.send(message)
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publisher.close()
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if wait:
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consumer.wait()
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if __name__ == "__main__":
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# NOTE(vish): you can send messages from the command line using
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# topic and a json sting representing a dictionary
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# for the method
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send_message(sys.argv[1], json.loads(sys.argv[2]))
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