diff --git a/synapse/util/distributor.py b/synapse/util/distributor.py
new file mode 100644
index 0000000000..32d19402b4
--- /dev/null
+++ b/synapse/util/distributor.py
@@ -0,0 +1,108 @@
+# -*- coding: utf-8 -*-
+# Copyright 2014 matrix.org
+#
+# 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.
+from twisted.internet import defer
+
+import logging
+
+
+logger = logging.getLogger(__name__)
+
+
+class Distributor(object):
+ """A central dispatch point for loosely-connected pieces of code to
+ register, observe, and fire signals.
+
+ Signals are named simply by strings.
+
+ TODO(paul): It would be nice to give signals stronger object identities,
+ so we can attach metadata, docstrings, detect typoes, etc... But this
+ model will do for today.
+ """
+
+ def __init__(self):
+ self.signals = {}
+ self.pre_registration = {}
+
+ def declare(self, name):
+ if name in self.signals:
+ raise KeyError("%r already has a signal named %s" % (self, name))
+
+ self.signals[name] = Signal(name)
+
+ if name in self.pre_registration:
+ signal = self.signals[name]
+ for observer in self.pre_registration[name]:
+ signal.observe(observer)
+
+ def observe(self, name, observer):
+ if name in self.signals:
+ self.signals[name].observe(observer)
+ else:
+ # TODO: Avoid strong ordering dependency by allowing people to
+ # pre-register observations on signals that don't exist yet.
+ if name not in self.pre_registration:
+ self.pre_registration[name] = []
+ self.pre_registration[name].append(observer)
+
+ def fire(self, name, *args, **kwargs):
+ if name not in self.signals:
+ raise KeyError("%r does not have a signal named %s" % (self, name))
+
+ return self.signals[name].fire(*args, **kwargs)
+
+
+class Signal(object):
+ """A Signal is a dispatch point that stores a list of callables as
+ observers of it.
+
+ Signals can be "fired", meaning that every callable observing it is
+ invoked. Firing a signal does not change its state; it can be fired again
+ at any later point. Firing a signal passes any arguments from the fire
+ method into all of the observers.
+ """
+
+ def __init__(self, name):
+ self.name = name
+ self.observers = []
+
+ def observe(self, observer):
+ """Adds a new callable to the observer list which will be invoked by
+ the 'fire' method.
+
+ Each observer callable may return a Deferred."""
+ self.observers.append(observer)
+
+ def fire(self, *args, **kwargs):
+ """Invokes every callable in the observer list, passing in the args and
+ kwargs. Exceptions thrown by observers are logged but ignored. It is
+ not an error to fire a signal with no observers.
+
+ Returns a Deferred that will complete when all the observers have
+ completed."""
+ deferreds = []
+ for observer in self.observers:
+ d = defer.maybeDeferred(observer, *args, **kwargs)
+
+ def eb(failure):
+ logger.warning(
+ "%s signal observer %s failed: %r",
+ self.name, observer, failure,
+ exc_info=(
+ failure.type,
+ failure.value,
+ failure.getTracebackObject()))
+ deferreds.append(d.addErrback(eb))
+
+ return defer.DeferredList(deferreds)
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