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diff --git a/openstack/common/rpc/dispatcher.py b/openstack/common/rpc/dispatcher.py
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+# vim: tabstop=4 shiftwidth=4 softtabstop=4
+
+# Copyright 2012 Red Hat, 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.
+
+"""
+Code for rpc message dispatching.
+
+Messages that come in have a version number associated with them.  RPC API
+version numbers are in the form:
+
+    Major.Minor
+
+For a given message with version X.Y, the receiver must be marked as able to
+handle messages of version A.B, where:
+
+    A = X
+
+    B >= Y
+
+The Major version number would be incremented for an almost completely new API.
+The Minor version number would be incremented for backwards compatible changes
+to an existing API.  A backwards compatible change could be something like
+adding a new method, adding an argument to an existing method (but not
+requiring it), or changing the type for an existing argument (but still
+handling the old type as well).
+
+The conversion over to a versioned API must be done on both the client side and
+server side of the API at the same time.  However, as the code stands today,
+there can be both versioned and unversioned APIs implemented in the same code
+base.
+"""
+
+from openstack.common.rpc import common as rpc_common
+
+
+class RpcDispatcher(object):
+    """Dispatch rpc messages according to the requested API version.
+
+    This class can be used as the top level 'manager' for a service.  It
+    contains a list of underlying managers that have an API_VERSION attribute.
+    """
+
+    def __init__(self, callbacks):
+        """Initialize the rpc dispatcher.
+
+        :param callbacks: List of proxy objects that are an instance
+                          of a class with rpc methods exposed.  Each proxy
+                          object should have an RPC_API_VERSION attribute.
+        """
+        self.callbacks = callbacks
+        super(RpcDispatcher, self).__init__()
+
+    @staticmethod
+    def _is_compatible(mversion, version):
+        """Determine whether versions are compatible.
+
+        :param mversion: The API version implemented by a callback.
+        :param version: The API version requested by an incoming message.
+        """
+        version_parts = version.split('.')
+        mversion_parts = mversion.split('.')
+        if int(version_parts[0]) != int(mversion_parts[0]):  # Major
+            return False
+        if int(version_parts[1]) > int(mversion_parts[1]):  # Minor
+            return False
+        return True
+
+    def dispatch(self, ctxt, version, method, **kwargs):
+        """Dispatch a message based on a requested version.
+
+        :param ctxt: The request context
+        :param version: The requested API version from the incoming message
+        :param method: The method requested to be called by the incoming
+                       message.
+        :param kwargs: A dict of keyword arguments to be passed to the method.
+
+        :returns: Whatever is returned by the underlying method that gets
+                  called.
+        """
+        if not version:
+            version = '1.0'
+
+        for proxyobj in self.callbacks:
+            if hasattr(proxyobj, 'RPC_API_VERSION'):
+                rpc_api_version = proxyobj.RPC_API_VERSION
+            else:
+                rpc_api_version = '1.0'
+            if not hasattr(proxyobj, method):
+                continue
+            if self._is_compatible(rpc_api_version, version):
+                return getattr(proxyobj, method)(ctxt, **kwargs)
+
+        raise rpc_common.UnsupportedRpcVersion(version=version)