# Copyright 2011 Cloudscaling Group, Inc # # Licensed under the Apache License, Version 2.0 (the "License"); you may # not use this file except in compliance with the License. You may obtain # a copy of the License at # # http://www.apache.org/licenses/LICENSE-2.0 # # Unless required by applicable law or agreed to in writing, software # distributed under the License is distributed on an "AS IS" BASIS, WITHOUT # WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the # License for the specific language governing permissions and limitations # under the License. import collections import logging import os import pprint import re import socket import sys import threading import types import uuid import eventlet import greenlet import six from six import moves from oslo.config import cfg from oslo.messaging._drivers import base from oslo.messaging._drivers import common as rpc_common from oslo.messaging._executors import impl_eventlet # FIXME(markmc) from oslo.messaging._i18n import _ from oslo.serialization import jsonutils from oslo.utils import excutils from oslo.utils import importutils zmq = importutils.try_import('eventlet.green.zmq') # for convenience, are not modified. pformat = pprint.pformat Timeout = eventlet.timeout.Timeout LOG = logging.getLogger(__name__) RPCException = rpc_common.RPCException zmq_opts = [ cfg.StrOpt('rpc_zmq_bind_address', default='*', help='ZeroMQ bind address. Should be a wildcard (*), ' 'an ethernet interface, or IP. ' 'The "host" option should point or resolve to this ' 'address.'), # The module.Class to use for matchmaking. cfg.StrOpt( 'rpc_zmq_matchmaker', default=('oslo.messaging._drivers.' 'matchmaker.MatchMakerLocalhost'), help='MatchMaker driver.', ), # The following port is unassigned by IANA as of 2012-05-21 cfg.IntOpt('rpc_zmq_port', default=9501, help='ZeroMQ receiver listening port.'), cfg.IntOpt('rpc_zmq_contexts', default=1, help='Number of ZeroMQ contexts, defaults to 1.'), cfg.IntOpt('rpc_zmq_topic_backlog', help='Maximum number of ingress messages to locally buffer ' 'per topic. Default is unlimited.'), cfg.StrOpt('rpc_zmq_ipc_dir', default='/var/run/openstack', help='Directory for holding IPC sockets.'), cfg.StrOpt('rpc_zmq_host', default=socket.gethostname(), sample_default='localhost', help='Name of this node. Must be a valid hostname, FQDN, or ' 'IP address. Must match "host" option, if running Nova.'), cfg.IntOpt('rpc_cast_timeout', default=30, help='Seconds to wait before a cast expires (TTL). ' 'Only supported by impl_zmq.'), ] CONF = cfg.CONF matchmaker = None # memoized matchmaker object def _serialize(data): """Serialization wrapper. We prefer using JSON, but it cannot encode all types. Error if a developer passes us bad data. """ try: return jsonutils.dumps(data, ensure_ascii=True) except TypeError: with excutils.save_and_reraise_exception(): LOG.error(_("JSON serialization failed.")) def _deserialize(data): """Deserialization wrapper.""" LOG.debug("Deserializing: %s", data) return jsonutils.loads(data) class ZmqSocket(object): """A tiny wrapper around ZeroMQ. Simplifies the send/recv protocol and connection management. Can be used as a Context (supports the 'with' statement). """ def __init__(self, addr, zmq_type, bind=True, subscribe=None): self.ctxt = zmq.Context(CONF.rpc_zmq_contexts) self.sock = self.ctxt.socket(zmq_type) self.addr = addr self.type = zmq_type self.subscriptions = [] # Support failures on sending/receiving on wrong socket type. self.can_recv = zmq_type in (zmq.PULL, zmq.SUB) self.can_send = zmq_type in (zmq.PUSH, zmq.PUB) self.can_sub = zmq_type in (zmq.SUB, ) # Support list, str, & None for subscribe arg (cast to list) do_sub = { list: subscribe, str: [subscribe], type(None): [] }[type(subscribe)] for f in do_sub: self.subscribe(f) str_data = {'addr': addr, 'type': self.socket_s(), 'subscribe': subscribe, 'bind': bind} LOG.debug("Connecting to %(addr)s with %(type)s", str_data) LOG.debug("-> Subscribed to %(subscribe)s", str_data) LOG.debug("-> bind: %(bind)s", str_data) try: if bind: self.sock.bind(addr) else: self.sock.connect(addr) except Exception: raise RPCException(_("Could not open socket.")) def socket_s(self): """Get socket type as string.""" t_enum = ('PUSH', 'PULL', 'PUB', 'SUB', 'REP', 'REQ', 'ROUTER', 'DEALER') return dict(map(lambda t: (getattr(zmq, t), t), t_enum))[self.type] def subscribe(self, msg_filter): """Subscribe.""" if not self.can_sub: raise RPCException("Cannot subscribe on this socket.") LOG.debug("Subscribing to %s", msg_filter) try: self.sock.setsockopt(zmq.SUBSCRIBE, msg_filter) except Exception: return self.subscriptions.append(msg_filter) def unsubscribe(self, msg_filter): """Unsubscribe.""" if msg_filter not in self.subscriptions: return self.sock.setsockopt(zmq.UNSUBSCRIBE, msg_filter) self.subscriptions.remove(msg_filter) def close(self): if self.sock is None or self.sock.closed: return # We must unsubscribe, or we'll leak descriptors. if self.subscriptions: for f in self.subscriptions: try: self.sock.setsockopt(zmq.UNSUBSCRIBE, f) except Exception: pass self.subscriptions = [] try: # Default is to linger self.sock.close() self.ctxt.term() except Exception: # While this is a bad thing to happen, # it would be much worse if some of the code calling this # were to fail. For now, lets log, and later evaluate # if we can safely raise here. LOG.error("ZeroMQ socket could not be closed.") self.sock = None def recv(self, **kwargs): if not self.can_recv: raise RPCException(_("You cannot recv on this socket.")) return self.sock.recv_multipart(**kwargs) def send(self, data, **kwargs): if not self.can_send: raise RPCException(_("You cannot send on this socket.")) self.sock.send_multipart(data, **kwargs) class ZmqClient(object): """Client for ZMQ sockets.""" def __init__(self, addr): self.outq = ZmqSocket(addr, zmq.PUSH, bind=False) def cast(self, msg_id, topic, data, envelope): msg_id = msg_id or 0 if not envelope: self.outq.send(map(bytes, (msg_id, topic, 'cast', _serialize(data)))) return rpc_envelope = rpc_common.serialize_msg(data[1]) zmq_msg = moves.reduce(lambda x, y: x + y, rpc_envelope.items()) self.outq.send(map(bytes, (msg_id, topic, 'impl_zmq_v2', data[0]) + zmq_msg)) def close(self): self.outq.close() class RpcContext(rpc_common.CommonRpcContext): """Context that supports replying to a rpc.call.""" def __init__(self, **kwargs): self.replies = [] super(RpcContext, self).__init__(**kwargs) def deepcopy(self): values = self.to_dict() values['replies'] = self.replies return self.__class__(**values) def reply(self, reply=None, failure=None, ending=False): if ending: return self.replies.append(reply) @classmethod def marshal(self, ctx): ctx_data = ctx.to_dict() return _serialize(ctx_data) @classmethod def unmarshal(self, data): return RpcContext.from_dict(_deserialize(data)) class InternalContext(object): """Used by ConsumerBase as a private context for - methods.""" def __init__(self, proxy): self.proxy = proxy self.msg_waiter = None def _get_response(self, ctx, proxy, topic, data): """Process a curried message and cast the result to topic.""" LOG.debug("Running func with context: %s", ctx.to_dict()) data.setdefault('version', None) data.setdefault('args', {}) try: result = proxy.dispatch( ctx, data['version'], data['method'], data.get('namespace'), **data['args']) return ConsumerBase.normalize_reply(result, ctx.replies) except greenlet.GreenletExit: # ignore these since they are just from shutdowns pass except rpc_common.ClientException as e: LOG.debug("Expected exception during message handling (%s)", e._exc_info[1]) return {'exc': rpc_common.serialize_remote_exception(e._exc_info, log_failure=False)} except Exception: LOG.error(_("Exception during message handling")) return {'exc': rpc_common.serialize_remote_exception(sys.exc_info())} def reply(self, ctx, proxy, msg_id=None, context=None, topic=None, msg=None): """Reply to a casted call.""" # NOTE(ewindisch): context kwarg exists for Grizzly compat. # this may be able to be removed earlier than # 'I' if ConsumerBase.process were refactored. if type(msg) is list: payload = msg[-1] else: payload = msg response = ConsumerBase.normalize_reply( self._get_response(ctx, proxy, topic, payload), ctx.replies) LOG.debug("Sending reply") _multi_send(_cast, ctx, topic, { 'method': '-process_reply', 'args': { 'msg_id': msg_id, # Include for Folsom compat. 'response': response } }, _msg_id=msg_id) class ConsumerBase(object): """Base Consumer.""" def __init__(self): self.private_ctx = InternalContext(None) @classmethod def normalize_reply(self, result, replies): # TODO(ewindisch): re-evaluate and document this method. if isinstance(result, types.GeneratorType): return list(result) elif replies: return replies else: return [result] def process(self, proxy, ctx, data): data.setdefault('version', None) data.setdefault('args', {}) # Method starting with - are # processed internally. (non-valid method name) method = data.get('method') if not method: LOG.error(_("RPC message did not include method.")) return # Internal method # uses internal context for safety. if method == '-reply': self.private_ctx.reply(ctx, proxy, **data['args']) return proxy.dispatch(ctx, data['version'], data['method'], data.get('namespace'), **data['args']) class ZmqBaseReactor(ConsumerBase): """A consumer class implementing a centralized casting broker (PULL-PUSH). Used for RoundRobin requests. """ def __init__(self, conf): super(ZmqBaseReactor, self).__init__() self.proxies = {} self.threads = [] self.sockets = [] self.subscribe = {} self.pool = eventlet.greenpool.GreenPool(conf.rpc_thread_pool_size) def register(self, proxy, in_addr, zmq_type_in, in_bind=True, subscribe=None): LOG.info(_("Registering reactor")) if zmq_type_in not in (zmq.PULL, zmq.SUB): raise RPCException("Bad input socktype") # Items push in. inq = ZmqSocket(in_addr, zmq_type_in, bind=in_bind, subscribe=subscribe) self.proxies[inq] = proxy self.sockets.append(inq) LOG.info(_("In reactor registered")) def consume_in_thread(self): def _consume(sock): LOG.info(_("Consuming socket")) while True: self.consume(sock) for k in self.proxies.keys(): self.threads.append( self.pool.spawn(_consume, k) ) def wait(self): for t in self.threads: t.wait() def close(self): for s in self.sockets: s.close() for t in self.threads: t.kill() class ZmqProxy(ZmqBaseReactor): """A consumer class implementing a topic-based proxy. Forwards to IPC sockets. """ def __init__(self, conf): super(ZmqProxy, self).__init__(conf) pathsep = set((os.path.sep or '', os.path.altsep or '', '/', '\\')) self.badchars = re.compile(r'[%s]' % re.escape(''.join(pathsep))) self.topic_proxy = {} def consume(self, sock): ipc_dir = CONF.rpc_zmq_ipc_dir data = sock.recv(copy=False) topic = data[1].bytes if topic.startswith('fanout~'): sock_type = zmq.PUB topic = topic.split('.', 1)[0] elif topic.startswith('zmq_replies'): sock_type = zmq.PUB else: sock_type = zmq.PUSH if topic not in self.topic_proxy: def publisher(waiter): LOG.info(_("Creating proxy for topic: %s"), topic) try: # The topic is received over the network, # don't trust this input. if self.badchars.search(topic) is not None: emsg = _("Topic contained dangerous characters.") LOG.warn(emsg) raise RPCException(emsg) out_sock = ZmqSocket("ipc://%s/zmq_topic_%s" % (ipc_dir, topic), sock_type, bind=True) except RPCException: waiter.send_exception(*sys.exc_info()) return self.topic_proxy[topic] = eventlet.queue.LightQueue( CONF.rpc_zmq_topic_backlog) self.sockets.append(out_sock) # It takes some time for a pub socket to open, # before we can have any faith in doing a send() to it. if sock_type == zmq.PUB: eventlet.sleep(.5) waiter.send(True) while(True): data = self.topic_proxy[topic].get() out_sock.send(data, copy=False) wait_sock_creation = eventlet.event.Event() eventlet.spawn(publisher, wait_sock_creation) try: wait_sock_creation.wait() except RPCException: LOG.error(_("Topic socket file creation failed.")) return try: self.topic_proxy[topic].put_nowait(data) except eventlet.queue.Full: LOG.error(_("Local per-topic backlog buffer full for topic " "%s. Dropping message."), topic) def consume_in_thread(self): """Runs the ZmqProxy service.""" ipc_dir = CONF.rpc_zmq_ipc_dir consume_in = "tcp://%s:%s" % \ (CONF.rpc_zmq_bind_address, CONF.rpc_zmq_port) consumption_proxy = InternalContext(None) try: os.makedirs(ipc_dir) except os.error: if not os.path.isdir(ipc_dir): with excutils.save_and_reraise_exception(): LOG.error(_("Required IPC directory does not exist at" " %s"), ipc_dir) try: self.register(consumption_proxy, consume_in, zmq.PULL) except zmq.ZMQError: if os.access(ipc_dir, os.X_OK): with excutils.save_and_reraise_exception(): LOG.error(_("Permission denied to IPC directory at" " %s"), ipc_dir) with excutils.save_and_reraise_exception(): LOG.error(_("Could not create ZeroMQ receiver daemon. " "Socket may already be in use.")) super(ZmqProxy, self).consume_in_thread() def unflatten_envelope(packenv): """Unflattens the RPC envelope. Takes a list and returns a dictionary. i.e. [1,2,3,4] => {1: 2, 3: 4} """ i = iter(packenv) h = {} try: while True: k = six.next(i) h[k] = six.next(i) except StopIteration: return h class ZmqReactor(ZmqBaseReactor): """A consumer class implementing a consumer for messages. Can also be used as a 1:1 proxy """ def __init__(self, conf): super(ZmqReactor, self).__init__(conf) def consume(self, sock): # TODO(ewindisch): use zero-copy (i.e. references, not copying) data = sock.recv() LOG.debug("CONSUMER RECEIVED DATA: %s", data) proxy = self.proxies[sock] if data[2] == 'cast': # Legacy protocol packenv = data[3] ctx, msg = _deserialize(packenv) request = rpc_common.deserialize_msg(msg) ctx = RpcContext.unmarshal(ctx) elif data[2] == 'impl_zmq_v2': packenv = data[4:] msg = unflatten_envelope(packenv) request = rpc_common.deserialize_msg(msg) # Unmarshal only after verifying the message. ctx = RpcContext.unmarshal(data[3]) else: LOG.error(_("ZMQ Envelope version unsupported or unknown.")) return self.pool.spawn_n(self.process, proxy, ctx, request) class Connection(rpc_common.Connection): """Manages connections and threads.""" def __init__(self, conf): self.topics = [] self.reactor = ZmqReactor(conf) def create_consumer(self, topic, proxy, fanout=False): # Register with matchmaker. _get_matchmaker().register(topic, CONF.rpc_zmq_host) # Subscription scenarios if fanout: sock_type = zmq.SUB subscribe = ('', fanout)[type(fanout) == str] topic = 'fanout~' + topic.split('.', 1)[0] else: sock_type = zmq.PULL subscribe = None topic = '.'.join((topic.split('.', 1)[0], CONF.rpc_zmq_host)) if topic in self.topics: LOG.info(_("Skipping topic registration. Already registered.")) return # Receive messages from (local) proxy inaddr = "ipc://%s/zmq_topic_%s" % \ (CONF.rpc_zmq_ipc_dir, topic) LOG.debug("Consumer is a zmq.%s", ['PULL', 'SUB'][sock_type == zmq.SUB]) self.reactor.register(proxy, inaddr, sock_type, subscribe=subscribe, in_bind=False) self.topics.append(topic) def close(self): _get_matchmaker().stop_heartbeat() for topic in self.topics: _get_matchmaker().unregister(topic, CONF.rpc_zmq_host) self.reactor.close() self.topics = [] def wait(self): self.reactor.wait() def consume_in_thread(self): _get_matchmaker().start_heartbeat() self.reactor.consume_in_thread() def _cast(addr, context, topic, msg, timeout=None, envelope=False, _msg_id=None, allowed_remote_exmods=None): allowed_remote_exmods = allowed_remote_exmods or [] timeout_cast = timeout or CONF.rpc_cast_timeout payload = [RpcContext.marshal(context), msg] with Timeout(timeout_cast, exception=rpc_common.Timeout): try: conn = ZmqClient(addr) # assumes cast can't return an exception conn.cast(_msg_id, topic, payload, envelope) except zmq.ZMQError: raise RPCException("Cast failed. ZMQ Socket Exception") finally: if 'conn' in vars(): conn.close() def _call(addr, context, topic, msg, timeout=None, envelope=False, allowed_remote_exmods=None): allowed_remote_exmods = allowed_remote_exmods or [] # timeout_response is how long we wait for a response timeout = timeout or CONF.rpc_response_timeout # The msg_id is used to track replies. msg_id = uuid.uuid4().hex # Replies always come into the reply service. reply_topic = "zmq_replies.%s" % CONF.rpc_zmq_host LOG.debug("Creating payload") # Curry the original request into a reply method. mcontext = RpcContext.marshal(context) payload = { 'method': '-reply', 'args': { 'msg_id': msg_id, 'topic': reply_topic, # TODO(ewindisch): safe to remove mcontext in I. 'msg': [mcontext, msg] } } LOG.debug("Creating queue socket for reply waiter") # Messages arriving async. # TODO(ewindisch): have reply consumer with dynamic subscription mgmt with Timeout(timeout, exception=rpc_common.Timeout): try: msg_waiter = ZmqSocket( "ipc://%s/zmq_topic_zmq_replies.%s" % (CONF.rpc_zmq_ipc_dir, CONF.rpc_zmq_host), zmq.SUB, subscribe=msg_id, bind=False ) LOG.debug("Sending cast") _cast(addr, context, topic, payload, envelope=envelope) LOG.debug("Cast sent; Waiting reply") # Blocks until receives reply msg = msg_waiter.recv() LOG.debug("Received message: %s", msg) LOG.debug("Unpacking response") if msg[2] == 'cast': # Legacy version raw_msg = _deserialize(msg[-1])[-1] elif msg[2] == 'impl_zmq_v2': rpc_envelope = unflatten_envelope(msg[4:]) raw_msg = rpc_common.deserialize_msg(rpc_envelope) else: raise rpc_common.UnsupportedRpcEnvelopeVersion( _("Unsupported or unknown ZMQ envelope returned.")) responses = raw_msg['args']['response'] # ZMQError trumps the Timeout error. except zmq.ZMQError: raise RPCException("ZMQ Socket Error") except (IndexError, KeyError): raise RPCException(_("RPC Message Invalid.")) finally: if 'msg_waiter' in vars(): msg_waiter.close() # It seems we don't need to do all of the following, # but perhaps it would be useful for multicall? # One effect of this is that we're checking all # responses for Exceptions. for resp in responses: if isinstance(resp, types.DictType) and 'exc' in resp: raise rpc_common.deserialize_remote_exception( resp['exc'], allowed_remote_exmods) return responses[-1] def _multi_send(method, context, topic, msg, timeout=None, envelope=False, _msg_id=None, allowed_remote_exmods=None): """Wraps the sending of messages. Dispatches to the matchmaker and sends message to all relevant hosts. """ allowed_remote_exmods = allowed_remote_exmods or [] conf = CONF LOG.debug(' '.join(map(pformat, (topic, msg)))) queues = _get_matchmaker().queues(topic) LOG.debug("Sending message(s) to: %s", queues) # Don't stack if we have no matchmaker results if not queues: LOG.warn(_("No matchmaker results. Not casting.")) # While not strictly a timeout, callers know how to handle # this exception and a timeout isn't too big a lie. raise rpc_common.Timeout(_("No match from matchmaker.")) # This supports brokerless fanout (addresses > 1) return_val = None for queue in queues: _topic, ip_addr = queue _addr = "tcp://%s:%s" % (ip_addr, conf.rpc_zmq_port) if method.__name__ == '_cast': eventlet.spawn_n(method, _addr, context, _topic, msg, timeout, envelope, _msg_id) else: return_val = method(_addr, context, _topic, msg, timeout, envelope, allowed_remote_exmods) return return_val def _get_matchmaker(*args, **kwargs): global matchmaker if not matchmaker: mm = CONF.rpc_zmq_matchmaker if mm.endswith('matchmaker.MatchMakerRing'): mm.replace('matchmaker', 'matchmaker_ring') LOG.warn(_('rpc_zmq_matchmaker = %(orig)s is deprecated; use' ' %(new)s instead') % dict( orig=CONF.rpc_zmq_matchmaker, new=mm)) matchmaker = importutils.import_object(mm, *args, **kwargs) return matchmaker class ZmqIncomingMessage(base.IncomingMessage): ReceivedReply = collections.namedtuple( 'ReceivedReply', ['reply', 'failure', 'log_failure']) def __init__(self, listener, ctxt, message): super(ZmqIncomingMessage, self).__init__(listener, ctxt, message) self.condition = threading.Condition() self.received = None def reply(self, reply=None, failure=None, log_failure=True): self.received = self.ReceivedReply(reply, failure, log_failure) with self.condition: self.condition.notify() def requeue(self): pass class ZmqListener(base.Listener): def __init__(self, driver): super(ZmqListener, self).__init__(driver) self.incoming_queue = moves.queue.Queue() def dispatch(self, ctxt, version, method, namespace, **kwargs): message = { 'method': method, 'args': kwargs } if version: message['version'] = version if namespace: message['namespace'] = namespace incoming = ZmqIncomingMessage(self, ctxt.to_dict(), message) self.incoming_queue.put(incoming) with incoming.condition: incoming.condition.wait() assert incoming.received if incoming.received.failure: raise incoming.received.failure else: return incoming.received.reply def poll(self, timeout=None): try: return self.incoming_queue.get(timeout=timeout) except six.moves.queue.Empty: # timeout return None class ZmqDriver(base.BaseDriver): # FIXME(markmc): allow this driver to be used without eventlet def __init__(self, conf, url, default_exchange=None, allowed_remote_exmods=None): if not zmq: raise ImportError("Failed to import eventlet.green.zmq") conf.register_opts(zmq_opts) conf.register_opts(impl_eventlet._eventlet_opts) super(ZmqDriver, self).__init__(conf, url, default_exchange, allowed_remote_exmods) # FIXME(markmc): handle default_exchange # FIXME(markmc): handle transport URL if self._url.hosts: raise NotImplementedError('The ZeroMQ driver does not yet support ' 'transport URLs') # FIXME(markmc): use self.conf everywhere if self.conf is not CONF: raise NotImplementedError('The ZeroMQ driver currently only works ' 'with oslo.config.cfg.CONF') def _send(self, target, ctxt, message, wait_for_reply=None, timeout=None, envelope=False): # FIXME(markmc): remove this temporary hack class Context(object): def __init__(self, d): self.d = d def to_dict(self): return self.d context = Context(ctxt) if wait_for_reply: method = _call else: method = _cast topic = target.topic if target.fanout: # NOTE(ewindisch): fanout~ is used because it avoid splitting on # and acts as a non-subtle hint to the matchmaker and ZmqProxy. topic = 'fanout~' + topic elif target.server: topic = '%s.%s' % (topic, target.server) reply = _multi_send(method, context, topic, message, envelope=envelope, allowed_remote_exmods=self._allowed_remote_exmods) if wait_for_reply: return reply[-1] def send(self, target, ctxt, message, wait_for_reply=None, timeout=None, retry=None): # NOTE(sileht): retry is not implemented because this driver never # retry anything return self._send(target, ctxt, message, wait_for_reply, timeout) def send_notification(self, target, ctxt, message, version, retry=None): # NOTE(ewindisch): dot-priority in rpc notifier does not # work with our assumptions. # NOTE(sileht): retry is not implemented because this driver never # retry anything target = target(topic=target.topic.replace('.', '-')) return self._send(target, ctxt, message, envelope=(version == 2.0)) def listen(self, target): conn = Connection(self.conf) listener = ZmqListener(self) conn.create_consumer(target.topic, listener) conn.create_consumer('%s.%s' % (target.topic, target.server), listener) conn.create_consumer(target.topic, listener, fanout=True) conn.consume_in_thread() return listener def listen_for_notifications(self, targets_and_priorities, pool): # NOTE(sileht): this listener implementation is limited # because zeromq doesn't support: # * requeing message # * pool conn = Connection(self.conf) listener = ZmqListener(self) for target, priority in targets_and_priorities: # NOTE(ewindisch): dot-priority in rpc notifier does not # work with our assumptions. # NOTE(sileht): create_consumer doesn't support target.exchange conn.create_consumer('%s-%s' % (target.topic, priority), listener) conn.consume_in_thread() return listener def cleanup(self): pass