322 lines
9.1 KiB
Python
322 lines
9.1 KiB
Python
# Copyright 2011 Cloudscaling Group, Inc
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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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The MatchMaker classes should except a Topic or Fanout exchange key and
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return keys for direct exchanges, per (approximate) AMQP parlance.
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"""
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import contextlib
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import logging
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import eventlet
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from oslo.config import cfg
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from oslo.messaging._i18n import _
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matchmaker_opts = [
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cfg.IntOpt('matchmaker_heartbeat_freq',
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default=300,
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help='Heartbeat frequency.'),
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cfg.IntOpt('matchmaker_heartbeat_ttl',
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default=600,
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help='Heartbeat time-to-live.'),
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]
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CONF = cfg.CONF
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CONF.register_opts(matchmaker_opts)
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LOG = logging.getLogger(__name__)
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contextmanager = contextlib.contextmanager
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class MatchMakerException(Exception):
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"""Signified a match could not be found."""
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message = _("Match not found by MatchMaker.")
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class Exchange(object):
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"""Implements lookups.
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Subclass this to support hashtables, dns, etc.
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"""
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def __init__(self):
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pass
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def run(self, key):
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raise NotImplementedError()
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class Binding(object):
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"""A binding on which to perform a lookup."""
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def __init__(self):
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pass
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def test(self, key):
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raise NotImplementedError()
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class MatchMakerBase(object):
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"""Match Maker Base Class.
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Build off HeartbeatMatchMakerBase if building a heartbeat-capable
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MatchMaker.
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"""
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def __init__(self):
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# Array of tuples. Index [2] toggles negation, [3] is last-if-true
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self.bindings = []
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self.no_heartbeat_msg = _('Matchmaker does not implement '
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'registration or heartbeat.')
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def register(self, key, host):
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"""Register a host on a backend.
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Heartbeats, if applicable, may keepalive registration.
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"""
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pass
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def ack_alive(self, key, host):
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"""Acknowledge that a key.host is alive.
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Used internally for updating heartbeats, but may also be used
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publicly to acknowledge a system is alive (i.e. rpc message
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successfully sent to host)
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"""
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pass
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def is_alive(self, topic, host):
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"""Checks if a host is alive."""
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pass
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def expire(self, topic, host):
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"""Explicitly expire a host's registration."""
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pass
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def send_heartbeats(self):
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"""Send all heartbeats.
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Use start_heartbeat to spawn a heartbeat greenthread,
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which loops this method.
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"""
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pass
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def unregister(self, key, host):
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"""Unregister a topic."""
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pass
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def start_heartbeat(self):
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"""Spawn heartbeat greenthread."""
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pass
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def stop_heartbeat(self):
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"""Destroys the heartbeat greenthread."""
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pass
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def add_binding(self, binding, rule, last=True):
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self.bindings.append((binding, rule, False, last))
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# NOTE(ewindisch): kept the following method in case we implement the
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# underlying support.
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# def add_negate_binding(self, binding, rule, last=True):
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# self.bindings.append((binding, rule, True, last))
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def queues(self, key):
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workers = []
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# bit is for negate bindings - if we choose to implement it.
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# last stops processing rules if this matches.
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for (binding, exchange, bit, last) in self.bindings:
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if binding.test(key):
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workers.extend(exchange.run(key))
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# Support last.
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if last:
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return workers
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return workers
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class HeartbeatMatchMakerBase(MatchMakerBase):
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"""Base for a heart-beat capable MatchMaker.
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Provides common methods for registering, unregistering, and maintaining
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heartbeats.
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"""
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def __init__(self):
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self.hosts = set()
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self._heart = None
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self.host_topic = {}
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super(HeartbeatMatchMakerBase, self).__init__()
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def send_heartbeats(self):
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"""Send all heartbeats.
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Use start_heartbeat to spawn a heartbeat greenthread,
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which loops this method.
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"""
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for key, host in self.host_topic:
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self.ack_alive(key, host)
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def ack_alive(self, key, host):
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"""Acknowledge that a host.topic is alive.
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Used internally for updating heartbeats, but may also be used
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publicly to acknowledge a system is alive (i.e. rpc message
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successfully sent to host)
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"""
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raise NotImplementedError("Must implement ack_alive")
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def backend_register(self, key, host):
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"""Implements registration logic.
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Called by register(self,key,host)
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"""
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raise NotImplementedError("Must implement backend_register")
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def backend_unregister(self, key, key_host):
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"""Implements de-registration logic.
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Called by unregister(self,key,host)
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"""
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raise NotImplementedError("Must implement backend_unregister")
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def register(self, key, host):
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"""Register a host on a backend.
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Heartbeats, if applicable, may keepalive registration.
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"""
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self.hosts.add(host)
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self.host_topic[(key, host)] = host
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key_host = '.'.join((key, host))
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self.backend_register(key, key_host)
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self.ack_alive(key, host)
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def unregister(self, key, host):
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"""Unregister a topic."""
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if (key, host) in self.host_topic:
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del self.host_topic[(key, host)]
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self.hosts.discard(host)
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self.backend_unregister(key, '.'.join((key, host)))
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LOG.info(_("Matchmaker unregistered: %(key)s, %(host)s"),
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{'key': key, 'host': host})
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def start_heartbeat(self):
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"""Implementation of MatchMakerBase.start_heartbeat.
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Launches greenthread looping send_heartbeats(),
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yielding for CONF.matchmaker_heartbeat_freq seconds
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between iterations.
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"""
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if not self.hosts:
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raise MatchMakerException(
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_("Register before starting heartbeat."))
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def do_heartbeat():
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while True:
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self.send_heartbeats()
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eventlet.sleep(CONF.matchmaker_heartbeat_freq)
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self._heart = eventlet.spawn(do_heartbeat)
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def stop_heartbeat(self):
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"""Destroys the heartbeat greenthread."""
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if self._heart:
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self._heart.kill()
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class DirectBinding(Binding):
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"""Specifies a host in the key via a '.' character.
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Although dots are used in the key, the behavior here is
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that it maps directly to a host, thus direct.
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"""
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def test(self, key):
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return '.' in key
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class TopicBinding(Binding):
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"""Where a 'bare' key without dots.
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AMQP generally considers topic exchanges to be those *with* dots,
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but we deviate here in terminology as the behavior here matches
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that of a topic exchange (whereas where there are dots, behavior
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matches that of a direct exchange.
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"""
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def test(self, key):
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return '.' not in key
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class FanoutBinding(Binding):
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"""Match on fanout keys, where key starts with 'fanout.' string."""
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def test(self, key):
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return key.startswith('fanout~')
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class StubExchange(Exchange):
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"""Exchange that does nothing."""
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def run(self, key):
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return [(key, None)]
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class LocalhostExchange(Exchange):
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"""Exchange where all direct topics are local."""
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def __init__(self, host='localhost'):
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self.host = host
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super(Exchange, self).__init__()
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def run(self, key):
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return [('.'.join((key.split('.')[0], self.host)), self.host)]
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class DirectExchange(Exchange):
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"""Exchange where all topic keys are split, sending to second half.
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i.e. "compute.host" sends a message to "compute.host" running on "host"
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"""
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def __init__(self):
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super(Exchange, self).__init__()
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def run(self, key):
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e = key.split('.', 1)[1]
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return [(key, e)]
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class MatchMakerLocalhost(MatchMakerBase):
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"""Match Maker where all bare topics resolve to localhost.
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Useful for testing.
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"""
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def __init__(self, host='localhost'):
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super(MatchMakerLocalhost, self).__init__()
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self.add_binding(FanoutBinding(), LocalhostExchange(host))
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self.add_binding(DirectBinding(), DirectExchange())
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self.add_binding(TopicBinding(), LocalhostExchange(host))
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class MatchMakerStub(MatchMakerBase):
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"""Match Maker where topics are untouched.
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Useful for testing, or for AMQP/brokered queues.
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Will not work where knowledge of hosts is known (i.e. zeromq)
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"""
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def __init__(self):
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super(MatchMakerStub, self).__init__()
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self.add_binding(FanoutBinding(), StubExchange())
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self.add_binding(DirectBinding(), StubExchange())
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self.add_binding(TopicBinding(), StubExchange())
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