1 files changed, 257 insertions, 0 deletions
diff --git a/openstack/common/rpc/matchmaker.py b/openstack/common/rpc/matchmaker.py
new file mode 100644
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+++ b/openstack/common/rpc/matchmaker.py
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+# vim: tabstop=4 shiftwidth=4 softtabstop=4
+
+#    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.
+"""
+The MatchMaker classes should except a Topic or Fanout exchange key and
+return keys for direct exchanges, per (approximate) AMQP parlance.
+"""
+
+import contextlib
+import itertools
+import json
+import logging
+
+from openstack.common import cfg
+
+
+matchmaker_opts = [
+    # Matchmaker ring file
+    cfg.StrOpt('matchmaker_ringfile',
+        default='/etc/nova/matchmaker_ring.json',
+        help='Matchmaker ring file (JSON)'),
+]
+
+CONF = cfg.CONF
+CONF.register_opts(matchmaker_opts)
+LOG = logging.getLogger(__name__)
+contextmanager = contextlib.contextmanager
+
+
+class MatchMakerException(Exception):
+    """Signified a match could not be found."""
+    message = _("Match not found by MatchMaker.")
+
+
+class Exchange(object):
+    """
+    Implements lookups.
+    Subclass this to support hashtables, dns, etc.
+    """
+    def __init__(self):
+        pass
+
+    def run(self, key):
+        raise NotImplementedError()
+
+
+class Binding(object):
+    """
+    A binding on which to perform a lookup.
+    """
+    def __init__(self):
+        pass
+
+    def test(self, key):
+        raise NotImplementedError()
+
+
+class MatchMakerBase(object):
+    """Match Maker Base Class."""
+
+    def __init__(self):
+        # Array of tuples. Index [2] toggles negation, [3] is last-if-true
+        self.bindings = []
+
+    def add_binding(self, binding, rule, last=True):
+        self.bindings.append((binding, rule, False, last))
+
+    #NOTE(ewindisch): kept the following method in case we implement the
+    #                 underlying support.
+    #def add_negate_binding(self, binding, rule, last=True):
+    #    self.bindings.append((binding, rule, True, last))
+
+    def queues(self, key):
+        workers = []
+
+        # bit is for negate bindings - if we choose to implement it.
+        # last stops processing rules if this matches.
+        for (binding, exchange, bit, last) in self.bindings:
+            if binding.test(key):
+                workers.extend(exchange.run(key))
+
+                # Support last.
+                if last:
+                    return workers
+        return workers
+
+
+class DirectBinding(Binding):
+    """
+    Specifies a host in the key via a '.' character
+    Although dots are used in the key, the behavior here is
+    that it maps directly to a host, thus direct.
+    """
+    def test(self, key):
+        if '.' in key:
+            return True
+        return False
+
+
+class TopicBinding(Binding):
+    """
+    Where a 'bare' key without dots.
+    AMQP generally considers topic exchanges to be those *with* dots,
+    but we deviate here in terminology as the behavior here matches
+    that of a topic exchange (whereas where there are dots, behavior
+    matches that of a direct exchange.
+    """
+    def test(self, key):
+        if '.' not in key:
+            return True
+        return False
+
+
+class FanoutBinding(Binding):
+    """Match on fanout keys, where key starts with 'fanout.' string."""
+    def test(self, key):
+        if key.startswith('fanout~'):
+            return True
+        return False
+
+
+class StubExchange(Exchange):
+    """Exchange that does nothing."""
+    def run(self, key):
+        return [(key, None)]
+
+
+class RingExchange(Exchange):
+    """
+    Match Maker where hosts are loaded from a static file containing
+    a hashmap (JSON formatted).
+
+    __init__ takes optional ring dictionary argument, otherwise
+    loads the ringfile from CONF.mathcmaker_ringfile.
+    """
+    def __init__(self, ring=None):
+        super(RingExchange, self).__init__()
+
+        if ring:
+            self.ring = ring
+        else:
+            fh = open(CONF.matchmaker_ringfile, 'r')
+            self.ring = json.load(fh)
+            fh.close()
+
+        self.ring0 = {}
+        for k in self.ring.keys():
+            self.ring0[k] = itertools.cycle(self.ring[k])
+
+    def _ring_has(self, key):
+        if key in self.ring0:
+            return True
+        return False
+
+
+class RoundRobinRingExchange(RingExchange):
+    """A Topic Exchange based on a hashmap."""
+    def __init__(self, ring=None):
+        super(RoundRobinRingExchange, self).__init__(ring)
+
+    def run(self, key):
+        if not self._ring_has(key):
+            LOG.warn(
+                _("No key defining hosts for topic '%s', "
+                  "see ringfile") % (key, )
+            )
+            return []
+        host = next(self.ring0[key])
+        return [(key + '.' + host, host)]
+
+
+class FanoutRingExchange(RingExchange):
+    """Fanout Exchange based on a hashmap."""
+    def __init__(self, ring=None):
+        super(FanoutRingExchange, self).__init__(ring)
+
+    def run(self, key):
+        # Assume starts with "fanout~", strip it for lookup.
+        nkey = key.split('fanout~')[1:][0]
+        if not self._ring_has(nkey):
+            LOG.warn(
+                _("No key defining hosts for topic '%s', "
+                  "see ringfile") % (nkey, )
+            )
+            return []
+        return map(lambda x: (key + '.' + x, x), self.ring[nkey])
+
+
+class LocalhostExchange(Exchange):
+    """Exchange where all direct topics are local."""
+    def __init__(self):
+        super(Exchange, self).__init__()
+
+    def run(self, key):
+        return [(key.split('.')[0] + '.localhost', 'localhost')]
+
+
+class DirectExchange(Exchange):
+    """
+    Exchange where all topic keys are split, sending to second half.
+    i.e. "compute.host" sends a message to "compute" running on "host"
+    """
+    def __init__(self):
+        super(Exchange, self).__init__()
+
+    def run(self, key):
+        b, e = key.split('.', 1)
+        return [(b, e)]
+
+
+class MatchMakerRing(MatchMakerBase):
+    """
+    Match Maker where hosts are loaded from a static hashmap.
+    """
+    def __init__(self, ring=None):
+        super(MatchMakerRing, self).__init__()
+        self.add_binding(FanoutBinding(), FanoutRingExchange(ring))
+        self.add_binding(DirectBinding(), DirectExchange())
+        self.add_binding(TopicBinding(), RoundRobinRingExchange(ring))
+
+
+class MatchMakerLocalhost(MatchMakerBase):
+    """
+    Match Maker where all bare topics resolve to localhost.
+    Useful for testing.
+    """
+    def __init__(self):
+        super(MatchMakerLocalhost, self).__init__()
+        self.add_binding(FanoutBinding(), LocalhostExchange())
+        self.add_binding(DirectBinding(), DirectExchange())
+        self.add_binding(TopicBinding(), LocalhostExchange())
+
+
+class MatchMakerStub(MatchMakerBase):
+    """
+    Match Maker where topics are untouched.
+    Useful for testing, or for AMQP/brokered queues.
+    Will not work where knowledge of hosts is known (i.e. zeromq)
+    """
+    def __init__(self):
+        super(MatchMakerLocalhost, self).__init__()
+
+        self.add_binding(FanoutBinding(), StubExchange())
+        self.add_binding(DirectBinding(), StubExchange())
+        self.add_binding(TopicBinding(), StubExchange())