227 lines
9.3 KiB
Python
227 lines
9.3 KiB
Python
# vim: tabstop=4 shiftwidth=4 softtabstop=4
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# Copyright 2012-2013 Red Hat, 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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A helper class for proxy objects to remote APIs.
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For more information about rpc API version numbers, see:
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rpc/dispatcher.py
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"""
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from muranorepository.openstack.common import rpc
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from muranorepository.openstack.common.rpc import common as rpc_common
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from muranorepository.openstack.common.rpc import serializer as rpc_serializer
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class RpcProxy(object):
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"""A helper class for rpc clients.
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This class is a wrapper around the RPC client API. It allows you to
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specify the topic and API version in a single place. This is intended to
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be used as a base class for a class that implements the client side of an
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rpc API.
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"""
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# The default namespace, which can be overriden in a subclass.
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RPC_API_NAMESPACE = None
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def __init__(self, topic, default_version, version_cap=None,
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serializer=None):
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"""Initialize an RpcProxy.
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:param topic: The topic to use for all messages.
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:param default_version: The default API version to request in all
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outgoing messages. This can be overridden on a per-message
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basis.
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:param version_cap: Optionally cap the maximum version used for sent
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messages.
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:param serializer: Optionaly (de-)serialize entities with a
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provided helper.
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"""
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self.topic = topic
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self.default_version = default_version
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self.version_cap = version_cap
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if serializer is None:
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serializer = rpc_serializer.NoOpSerializer()
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self.serializer = serializer
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super(RpcProxy, self).__init__()
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def _set_version(self, msg, vers):
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"""Helper method to set the version in a message.
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:param msg: The message having a version added to it.
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:param vers: The version number to add to the message.
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"""
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v = vers if vers else self.default_version
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if (self.version_cap and not
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rpc_common.version_is_compatible(self.version_cap, v)):
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raise rpc_common.RpcVersionCapError(version_cap=self.version_cap)
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msg['version'] = v
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def _get_topic(self, topic):
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"""Return the topic to use for a message."""
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return topic if topic else self.topic
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def can_send_version(self, version):
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"""Check to see if a version is compatible with the version cap."""
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return (not self.version_cap or
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rpc_common.version_is_compatible(self.version_cap, version))
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@staticmethod
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def make_namespaced_msg(method, namespace, **kwargs):
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return {'method': method, 'namespace': namespace, 'args': kwargs}
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def make_msg(self, method, **kwargs):
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return self.make_namespaced_msg(method, self.RPC_API_NAMESPACE,
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**kwargs)
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def _serialize_msg_args(self, context, kwargs):
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"""Helper method called to serialize message arguments.
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This calls our serializer on each argument, returning a new
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set of args that have been serialized.
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:param context: The request context
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:param kwargs: The arguments to serialize
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:returns: A new set of serialized arguments
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"""
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new_kwargs = dict()
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for argname, arg in kwargs.iteritems():
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new_kwargs[argname] = self.serializer.serialize_entity(context,
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arg)
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return new_kwargs
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def call(self, context, msg, topic=None, version=None, timeout=None):
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"""rpc.call() a remote method.
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:param context: The request context
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:param msg: The message to send, including the method and args.
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:param topic: Override the topic for this message.
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:param version: (Optional) Override the requested API version in this
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message.
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:param timeout: (Optional) A timeout to use when waiting for the
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response. If no timeout is specified, a default timeout will be
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used that is usually sufficient.
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:returns: The return value from the remote method.
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"""
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self._set_version(msg, version)
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msg['args'] = self._serialize_msg_args(context, msg['args'])
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real_topic = self._get_topic(topic)
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try:
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result = rpc.call(context, real_topic, msg, timeout)
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return self.serializer.deserialize_entity(context, result)
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except rpc.common.Timeout as exc:
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raise rpc.common.Timeout(
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exc.info, real_topic, msg.get('method'))
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def multicall(self, context, msg, topic=None, version=None, timeout=None):
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"""rpc.multicall() a remote method.
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:param context: The request context
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:param msg: The message to send, including the method and args.
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:param topic: Override the topic for this message.
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:param version: (Optional) Override the requested API version in this
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message.
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:param timeout: (Optional) A timeout to use when waiting for the
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response. If no timeout is specified, a default timeout will be
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used that is usually sufficient.
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:returns: An iterator that lets you process each of the returned values
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from the remote method as they arrive.
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"""
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self._set_version(msg, version)
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msg['args'] = self._serialize_msg_args(context, msg['args'])
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real_topic = self._get_topic(topic)
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try:
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result = rpc.multicall(context, real_topic, msg, timeout)
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return self.serializer.deserialize_entity(context, result)
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except rpc.common.Timeout as exc:
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raise rpc.common.Timeout(
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exc.info, real_topic, msg.get('method'))
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def cast(self, context, msg, topic=None, version=None):
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"""rpc.cast() a remote method.
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:param context: The request context
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:param msg: The message to send, including the method and args.
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:param topic: Override the topic for this message.
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:param version: (Optional) Override the requested API version in this
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message.
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:returns: None. rpc.cast() does not wait on any return value from the
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remote method.
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"""
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self._set_version(msg, version)
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msg['args'] = self._serialize_msg_args(context, msg['args'])
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rpc.cast(context, self._get_topic(topic), msg)
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def fanout_cast(self, context, msg, topic=None, version=None):
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"""rpc.fanout_cast() a remote method.
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:param context: The request context
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:param msg: The message to send, including the method and args.
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:param topic: Override the topic for this message.
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:param version: (Optional) Override the requested API version in this
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message.
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:returns: None. rpc.fanout_cast() does not wait on any return value
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from the remote method.
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"""
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self._set_version(msg, version)
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msg['args'] = self._serialize_msg_args(context, msg['args'])
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rpc.fanout_cast(context, self._get_topic(topic), msg)
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def cast_to_server(self, context, server_params, msg, topic=None,
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version=None):
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"""rpc.cast_to_server() a remote method.
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:param context: The request context
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:param server_params: Server parameters. See rpc.cast_to_server() for
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details.
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:param msg: The message to send, including the method and args.
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:param topic: Override the topic for this message.
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:param version: (Optional) Override the requested API version in this
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message.
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:returns: None. rpc.cast_to_server() does not wait on any
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return values.
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"""
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self._set_version(msg, version)
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msg['args'] = self._serialize_msg_args(context, msg['args'])
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rpc.cast_to_server(context, server_params, self._get_topic(topic), msg)
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def fanout_cast_to_server(self, context, server_params, msg, topic=None,
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version=None):
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"""rpc.fanout_cast_to_server() a remote method.
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:param context: The request context
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:param server_params: Server parameters. See rpc.cast_to_server() for
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details.
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:param msg: The message to send, including the method and args.
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:param topic: Override the topic for this message.
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:param version: (Optional) Override the requested API version in this
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message.
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:returns: None. rpc.fanout_cast_to_server() does not wait on any
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return values.
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"""
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self._set_version(msg, version)
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msg['args'] = self._serialize_msg_args(context, msg['args'])
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rpc.fanout_cast_to_server(context, server_params,
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self._get_topic(topic), msg)
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