def dispatch(self, ctxt, version, method, namespace, **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 namespace: The namespace for the requested method. If None,
the dispatcher will look for a method on a callback
object with no namespace set.
: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'
had_compatible = False
for proxyobj in self.callbacks:
# Check for namespace compatibility
try:
cb_namespace = proxyobj.RPC_API_NAMESPACE
except AttributeError:
cb_namespace = None
if namespace != cb_namespace:
continue
# Check for version compatibility
try:
rpc_api_version = proxyobj.RPC_API_VERSION
except AttributeError:
rpc_api_version = '1.0'
is_compatible = rpc_common.version_is_compatible(rpc_api_version,
version)
had_compatible = had_compatible or is_compatible
if not hasattr(proxyobj, method):
continue
if is_compatible:
kwargs = self._deserialize_args(ctxt, kwargs)
result = getattr(proxyobj, method)(ctxt, **kwargs)
return self.serializer.serialize_entity(ctxt, result)
if had_compatible:
raise AttributeError("No such RPC function '%s'" % method)
else:
raise rpc_common.UnsupportedRpcVersion(version=version)