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