Distinguish the source of requests

1. What is the problem?
When receiving a request, we don't know whether the request
comes from  'Central Neutron' or 'Local Neutron'.

2. What is the solution to the problem?
In order to determine the source of requests, we add a
filter to get the source message in the header of requests.
Next step we tag the source message into the context. When
deploy the WSGI app, we checkout the User-Agent in the
request's headers and tag the requests.

3. What the features need to be implemented to the Tricircle
to realize the solution?
No

Change-Id: I990fa46e887cc0822b8e6d74d199d92e39df0bd6

devstack/plugin.sh

@@ -327,6 +327,14 @@ function start_central_neutron_server {
     iniset $NEUTRON_CONF.$server_index tricircle type_drivers $type_drivers
     iniset $NEUTRON_CONF.$server_index tricircle tenant_network_types $tenant_network_types
     iniset $NEUTRON_CONF.$server_index tricircle enable_api_gateway False
+
+    # reconfigure api-paste.ini in central neutron server
+    local API_PASTE_INI=$NEUTRON_CONF_DIR/api-paste.ini
+    sudo sed -e "
+        /^keystone.*neutronapiapp/s/neutronapiapp/request_source &/;
+        /app:neutronapiapp/i\[filter:request_source]\npaste.filter_factory = tricircle.common.request_source:RequestSource.factory\n
+    " -i $API_PASTE_INI
+
     # default value of bridge_network_type is vxlan
 
     if [ "$TRICIRCLE_ENABLE_QOS" == "True" ]; then

tricircle/common/constants.py

@@ -218,3 +218,11 @@ job_primary_resource_map = {
 # admin API request path
 ROUTING_PATH = '/v1.0/routings'
 JOB_PATH = '/v1.0/jobs'
+
+USER_AGENT = 'User-Agent'
+# The name of the source flag when the request is from central Neutron
+CENTRAL = 'central-neutronclient'
+# The name of the source flag when the request is from local Neutron
+LOCAL = 'local-neutronclient'
+
+REQUEST_SOURCE_TYPE = set([CENTRAL, LOCAL])

tricircle/common/request_source.py

@@ -0,0 +1,47 @@
+#    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.
+from oslo_log import log as logging
+from oslo_middleware import base
+import webob
+
+import constants as cons
+
+LOG = logging.getLogger(__name__)
+
+
+class RequestSource(base.ConfigurableMiddleware):
+    """RequestSource Middleware
+
+    This middleware distinguishes the source of the requests. It can find out
+    which request is from central Neutron and which is from local Neutron.
+
+    This middleware updates the context to put the source of requests
+    extracted from headers.
+
+    In order to make RequestSource Middleware work, this middleware should
+    place after keystoneContext(in etc/neutron/api-paste.ini).
+    """
+
+    def distinguish_requests_source(self, req):
+        source_header = req.headers.get(cons.USER_AGENT, "")
+
+        if source_header in cons.REQUEST_SOURCE_TYPE:
+            ctx = req.environ['neutron.context']
+            ctx.USER_AGENT = source_header
+            req.environ['neutron.context'] = ctx
+
+    @webob.dec.wsgify
+    def __call__(self, req):
+        self.distinguish_requests_source(req)
+
+        response = req.get_response(self.application)
+        return response

tricircle/network/central_plugin.py

@@ -60,6 +60,7 @@ from neutron_lib import constants
 from neutron_lib import exceptions
 from neutron_lib.exceptions import availability_zone as az_exc
 from neutron_lib.plugins import directory
+import neutronclient.client as neutronclient
 import neutronclient.common.exceptions as q_cli_exceptions
 
 from sqlalchemy import sql
@@ -184,6 +185,7 @@ class TricirclePlugin(db_base_plugin_v2.NeutronDbPluginV2,
         self.extension_manager.initialize()
         self.type_manager.initialize()
         self.helper = helper.NetworkHelper(self)
+        neutronclient.USER_AGENT = t_constants.CENTRAL
         qos_driver.register()
 
     def _setup_rpc(self):

tricircle/network/local_plugin.py

@@ -26,6 +26,7 @@ import neutron_lib.constants as q_constants
 import neutron_lib.exceptions as q_exceptions
 from neutron_lib.plugins import directory
 from neutron_lib.utils import runtime
+import neutronclient.client as neutronclient
 
 from neutron.common import utils
 import neutron.extensions.securitygroup as ext_sg
@@ -78,6 +79,7 @@ class TricirclePlugin(plugin.Ml2Plugin):
             cfg.CONF.tricircle.central_neutron_url
         self.on_trunk_create = {}
         self.on_subnet_delete = {}
+        neutronclient.USER_AGENT = t_constants.LOCAL
 
     def start_rpc_listeners(self):
         return self.core_plugin.start_rpc_listeners()