Add rpc to openstack-common.

Implements blueprint common-rpc.

This patch imports nova.rpc to openstack-common.  All of the necessary
changes to the core code to make it compatible with openstack-common
have been done in nova, so the only changes made here are to imports.

There are more changes made to the tests, but nothing that changes the
core functionality of the tests.

Change-Id: I17330aa4adfd0f22c449a2376833c7fe9dfd0cf1

1 files changed, 248 insertions, 0 deletions

diff --git a/openstack/common/rpc/__init__.py b/openstack/common/rpc/__init__.py
new file mode 100644
index 0000000..116aa84
--- /dev/null
+++ b/openstack/common/rpc/__init__.py
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+# vim: tabstop=4 shiftwidth=4 softtabstop=4
+
+# Copyright 2010 United States Government as represented by the
+# Administrator of the National Aeronautics and Space Administration.
+# All Rights Reserved.
+# Copyright 2011 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 remote procedure call (rpc) abstraction.
+
+For some wrappers that add message versioning to rpc, see:
+    rpc.dispatcher
+    rpc.proxy
+"""
+
+from openstack.common import cfg
+from openstack.common import importutils
+
+
+rpc_opts = [
+    cfg.StrOpt('rpc_backend',
+               default='nova.rpc.impl_kombu',
+               help="The messaging module to use, defaults to kombu."),
+    cfg.IntOpt('rpc_thread_pool_size',
+               default=64,
+               help='Size of RPC thread pool'),
+    cfg.IntOpt('rpc_conn_pool_size',
+               default=30,
+               help='Size of RPC connection pool'),
+    cfg.IntOpt('rpc_response_timeout',
+               default=60,
+               help='Seconds to wait for a response from call or multicall'),
+    cfg.ListOpt('allowed_rpc_exception_modules',
+                default=['openstack.common.exception', 'nova.exception'],
+                help='Modules of exceptions that are permitted to be recreated'
+                     'upon receiving exception data from an rpc call.'),
+    cfg.StrOpt('control_exchange',
+               default='nova',
+               help='AMQP exchange to connect to if using RabbitMQ or Qpid'),
+    cfg.BoolOpt('fake_rabbit',
+                default=False,
+                help='If passed, use a fake RabbitMQ provider'),
+    ]
+
+cfg.CONF.register_opts(rpc_opts)
+
+
+def create_connection(new=True):
+    """Create a connection to the message bus used for rpc.
+
+    For some example usage of creating a connection and some consumers on that
+    connection, see nova.service.
+
+    :param new: Whether or not to create a new connection.  A new connection
+                will be created by default.  If new is False, the
+                implementation is free to return an existing connection from a
+                pool.
+
+    :returns: An instance of nova.rpc.common.Connection
+    """
+    return _get_impl().create_connection(cfg.CONF, new=new)
+
+
+def call(context, topic, msg, timeout=None):
+    """Invoke a remote method that returns something.
+
+    :param context: Information that identifies the user that has made this
+                    request.
+    :param topic: The topic to send the rpc message to.  This correlates to the
+                  topic argument of
+                  nova.rpc.common.Connection.create_consumer() and only applies
+                  when the consumer was created with fanout=False.
+    :param msg: This is a dict in the form { "method" : "method_to_invoke",
+                                             "args" : dict_of_kwargs }
+    :param timeout: int, number of seconds to use for a response timeout.
+                    If set, this overrides the rpc_response_timeout option.
+
+    :returns: A dict from the remote method.
+
+    :raises: nova.rpc.common.Timeout if a complete response is not received
+             before the timeout is reached.
+    """
+    return _get_impl().call(cfg.CONF, context, topic, msg, timeout)
+
+
+def cast(context, topic, msg):
+    """Invoke a remote method that does not return anything.
+
+    :param context: Information that identifies the user that has made this
+                    request.
+    :param topic: The topic to send the rpc message to.  This correlates to the
+                  topic argument of
+                  nova.rpc.common.Connection.create_consumer() and only applies
+                  when the consumer was created with fanout=False.
+    :param msg: This is a dict in the form { "method" : "method_to_invoke",
+                                             "args" : dict_of_kwargs }
+
+    :returns: None
+    """
+    return _get_impl().cast(cfg.CONF, context, topic, msg)
+
+
+def fanout_cast(context, topic, msg):
+    """Broadcast a remote method invocation with no return.
+
+    This method will get invoked on all consumers that were set up with this
+    topic name and fanout=True.
+
+    :param context: Information that identifies the user that has made this
+                    request.
+    :param topic: The topic to send the rpc message to.  This correlates to the
+                  topic argument of
+                  nova.rpc.common.Connection.create_consumer() and only applies
+                  when the consumer was created with fanout=True.
+    :param msg: This is a dict in the form { "method" : "method_to_invoke",
+                                             "args" : dict_of_kwargs }
+
+    :returns: None
+    """
+    return _get_impl().fanout_cast(cfg.CONF, context, topic, msg)
+
+
+def multicall(context, topic, msg, timeout=None):
+    """Invoke a remote method and get back an iterator.
+
+    In this case, the remote method will be returning multiple values in
+    separate messages, so the return values can be processed as the come in via
+    an iterator.
+
+    :param context: Information that identifies the user that has made this
+                    request.
+    :param topic: The topic to send the rpc message to.  This correlates to the
+                  topic argument of
+                  nova.rpc.common.Connection.create_consumer() and only applies
+                  when the consumer was created with fanout=False.
+    :param msg: This is a dict in the form { "method" : "method_to_invoke",
+                                             "args" : dict_of_kwargs }
+    :param timeout: int, number of seconds to use for a response timeout.
+                    If set, this overrides the rpc_response_timeout option.
+
+    :returns: An iterator.  The iterator will yield a tuple (N, X) where N is
+              an index that starts at 0 and increases by one for each value
+              returned and X is the Nth value that was returned by the remote
+              method.
+
+    :raises: nova.rpc.common.Timeout if a complete response is not received
+             before the timeout is reached.
+    """
+    return _get_impl().multicall(cfg.CONF, context, topic, msg, timeout)
+
+
+def notify(context, topic, msg):
+    """Send notification event.
+
+    :param context: Information that identifies the user that has made this
+                    request.
+    :param topic: The topic to send the notification to.
+    :param msg: This is a dict of content of event.
+
+    :returns: None
+    """
+    return _get_impl().notify(cfg.CONF, context, topic, msg)
+
+
+def cleanup():
+    """Clean up resoruces in use by implementation.
+
+    Clean up any resources that have been allocated by the RPC implementation.
+    This is typically open connections to a messaging service.  This function
+    would get called before an application using this API exits to allow
+    connections to get torn down cleanly.
+
+    :returns: None
+    """
+    return _get_impl().cleanup()
+
+
+def cast_to_server(context, server_params, topic, msg):
+    """Invoke a remote method that does not return anything.
+
+    :param context: Information that identifies the user that has made this
+                    request.
+    :param server_params: Connection information
+    :param topic: The topic to send the notification to.
+    :param msg: This is a dict in the form { "method" : "method_to_invoke",
+                                             "args" : dict_of_kwargs }
+
+    :returns: None
+    """
+    return _get_impl().cast_to_server(cfg.CONF, context, server_params, topic,
+                                      msg)
+
+
+def fanout_cast_to_server(context, server_params, topic, msg):
+    """Broadcast to a remote method invocation with no return.
+
+    :param context: Information that identifies the user that has made this
+                    request.
+    :param server_params: Connection information
+    :param topic: The topic to send the notification to.
+    :param msg: This is a dict in the form { "method" : "method_to_invoke",
+                                             "args" : dict_of_kwargs }
+
+    :returns: None
+    """
+    return _get_impl().fanout_cast_to_server(cfg.CONF, context, server_params,
+                                             topic, msg)
+
+
+def queue_get_for(context, topic, host):
+    """Get a queue name for a given topic + host.
+
+    This function only works if this naming convention is followed on the
+    consumer side, as well.  For example, in nova, every instance of the
+    nova-foo service calls create_consumer() for two topics:
+
+        foo
+        foo.<host>
+
+    Messages sent to the 'foo' topic are distributed to exactly one instance of
+    the nova-foo service.  The services are chosen in a round-robin fashion.
+    Messages sent to the 'foo.<host>' topic are sent to the nova-foo service on
+    <host>.
+    """
+    return '%s.%s' % (topic, host)
+
+
+_RPCIMPL = None
+
+
+def _get_impl():
+    """Delay import of rpc_backend until configuration is loaded."""
+    global _RPCIMPL
+    if _RPCIMPL is None:
+        _RPCIMPL = importutils.import_module(cfg.CONF.rpc_backend)
+    return _RPCIMPL