Introduce a separate RPC server

As the Pecan server only server REST requests over HTTP, this
patch introduces a new server implementing the RPC over AMQP
endpoints for agent/server communication.

However, the REST server does not yet have the ability to send
notifications to the RPC server or directly to the agents.
This patch simply adapts the ML2 plugin to run the RPC notifiers
only when initialized in the pecan server, so that notification
to agents can still be sent.

This patch therefore is tantamount to a poor man's
implementation of REST/RPC separation which will be iteratively
improved.

Change-Id: Ie471869d9b2793acdc412f13507038433f6a72c6

neutron/cmd/eventlet/server/__init__.py

@@ -10,14 +10,20 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
+from neutron.server import rpc_eventlet
 from neutron.server import wsgi_eventlet
 from neutron.server import wsgi_pecan
 
 
 def main_wsgi_eventlet():
-    # This also starts the RPC server
     wsgi_eventlet.main()
 
 
+# Eventlet patching is not required for Pecan, but some plugins still spawn
+# eventlet threads
 def main_wsgi_pecan():
     wsgi_pecan.main()
+
+
+def main_rpc_eventlet():
+    rpc_eventlet.main()

neutron/plugins/ml2/plugin.py

@@ -146,17 +146,12 @@ class Ml2Plugin(db_base_plugin_v2.NeutronDbPluginV2,
         self.type_manager.initialize()
         self.extension_manager.initialize()
         self.mechanism_manager.initialize()
-
-        self._setup_rpc()
         self._setup_dhcp()
+        self._start_rpc_notifiers()
         LOG.info(_LI("Modular L2 Plugin initialization complete"))
 
     def _setup_rpc(self):
         """Initialize components to support agent communication."""
-        self.notifier = rpc.AgentNotifierApi(topics.AGENT)
-        self.agent_notifiers[const.AGENT_TYPE_DHCP] = (
-            dhcp_rpc_agent_api.DhcpAgentNotifyAPI()
-        )
         self.endpoints = [
             rpc.RpcCallbacks(self.notifier, self.type_manager),
             securitygroups_rpc.SecurityGroupServerRpcCallback(),
@@ -178,9 +173,18 @@ class Ml2Plugin(db_base_plugin_v2.NeutronDbPluginV2,
     def supported_qos_rule_types(self):
         return self.mechanism_manager.supported_qos_rule_types
 
+    @log_helpers.log_method_call
+    def _start_rpc_notifiers(self):
+        """Initialize RPC notifiers for agents."""
+        self.notifier = rpc.AgentNotifierApi(topics.AGENT)
+        self.agent_notifiers[const.AGENT_TYPE_DHCP] = (
+            dhcp_rpc_agent_api.DhcpAgentNotifyAPI()
+        )
+
     @log_helpers.log_method_call
     def start_rpc_listeners(self):
         """Start the RPC loop to let the plugin communicate with agents."""
+        self._setup_rpc()
         self.topic = topics.PLUGIN
         self.conn = n_rpc.create_connection(new=True)
         self.conn.create_consumer(self.topic, self.endpoints, fanout=False)

neutron/server/rpc_eventlet.py

@@ -0,0 +1,45 @@
+#!/usr/bin/env python
+
+# Copyright 2011 VMware, Inc.
+# All Rights Reserved.
+#
+#    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.
+
+# If ../neutron/__init__.py exists, add ../ to Python search path, so that
+# it will override what happens to be installed in /usr/(local/)lib/python...
+
+import eventlet
+from oslo_log import log
+
+from neutron.i18n import _LI
+from neutron import server
+from neutron import service
+
+LOG = log.getLogger(__name__)
+
+
+def _eventlet_rpc_server():
+    pool = eventlet.GreenPool()
+    LOG.info(_LI("Eventlet based AMQP RPC server starting..."))
+    try:
+        neutron_rpc = service.serve_rpc()
+    except NotImplementedError:
+        LOG.info(_LI("RPC was already started in parent process by "
+                     "plugin."))
+    else:
+        pool.spawn(neutron_rpc.wait)
+    pool.waitall()
+
+
+def main():
+    server.boot_server(_eventlet_rpc_server)

setup.cfg

@@ -97,6 +97,7 @@ console_scripts =
     neutron-restproxy-agent = neutron.plugins.bigswitch.agent.restproxy_agent:main
     neutron-server = neutron.cmd.eventlet.server:main_wsgi_eventlet
     neutron-dev-server = neutron.cmd.eventlet.server:main_wsgi_pecan
+    neutron-rpc-server = neutron.cmd.eventlet.server:main_rpc_eventlet
     neutron-rootwrap = oslo_rootwrap.cmd:main
     neutron-rootwrap-daemon = oslo_rootwrap.cmd:daemon
     neutron-usage-audit = neutron.cmd.usage_audit:main