Add option to ignore backend HTTP error in BigSwitch plugin

This patch fixes the way the BigSwitch plugin ignores 404
errors from the backend controller by allowing HTTP codes
to be selectively ignored on REST calls. This prevents
unnecessary exception handling and failover logic in calls
where 404 codes are acceptable.

Change-Id: Ia1118c039af3b45d96fb3f8a5fb5d3febdf50f4f
Fixes: bug #1200023

neutron/plugins/bigswitch/plugin.py

@@ -268,13 +268,13 @@ class ServerPool(object):
         return ServerProxy(server, port, self.ssl, self.auth, self.neutron_id,
                            self.timeout, self.base_uri, self.name)
 
-    def server_failure(self, resp):
+    def server_failure(self, resp, ignore_codes=[]):
         """Define failure codes as required.
 
         Note: We assume 301-303 is a failure, and try the next server in
         the server pool.
         """
-        return resp[0] in FAILURE_CODES
+        return (resp[0] in FAILURE_CODES and resp[0] not in ignore_codes)
 
     def action_success(self, resp):
         """Defining success codes as required.
@@ -283,12 +283,12 @@ class ServerPool(object):
         """
         return resp[0] in SUCCESS_CODES
 
-    def rest_call(self, action, resource, data, headers):
+    def rest_call(self, action, resource, data, headers, ignore_codes):
         failed_servers = []
         while self.servers:
             active_server = self.servers[0]
             ret = active_server.rest_call(action, resource, data, headers)
-            if not self.server_failure(ret):
+            if not self.server_failure(ret, ignore_codes):
                 self.servers.extend(failed_servers)
                 return ret
             else:
@@ -308,17 +308,17 @@ class ServerPool(object):
         self.servers.extend(failed_servers)
         return (0, None, None, None)
 
-    def get(self, resource, data='', headers=None):
-        return self.rest_call('GET', resource, data, headers)
+    def get(self, resource, data='', headers=None, ignore_codes=[]):
+        return self.rest_call('GET', resource, data, headers, ignore_codes)
 
-    def put(self, resource, data, headers=None):
-        return self.rest_call('PUT', resource, data, headers)
+    def put(self, resource, data, headers=None, ignore_codes=[]):
+        return self.rest_call('PUT', resource, data, headers, ignore_codes)
 
-    def post(self, resource, data, headers=None):
-        return self.rest_call('POST', resource, data, headers)
+    def post(self, resource, data, headers=None, ignore_codes=[]):
+        return self.rest_call('POST', resource, data, headers, ignore_codes)
 
-    def delete(self, resource, data='', headers=None):
-        return self.rest_call('DELETE', resource, data, headers)
+    def delete(self, resource, data='', headers=None, ignore_codes=[]):
+        return self.rest_call('DELETE', resource, data, headers, ignore_codes)
 
 
 class RpcProxy(dhcp_rpc_base.DhcpRpcCallbackMixin):
@@ -790,12 +790,13 @@ class NeutronRestProxyV2(db_base_plugin_v2.NeutronDbPluginV2,
         # delete from network ctrl. Remote error on delete is ignored
         try:
             resource = ATTACHMENT_PATH % (tenant_id, net_id, port_id)
-            ret = self.servers.delete(resource)
-            if not self.servers.action_success(ret):
+            ret = self.servers.delete(resource, ignore_codes=[404])
+            if self.servers.server_failure(ret, ignore_codes=[404]):
                 raise RemoteRestError(ret[2])
         except RemoteRestError as e:
             LOG.error(_("NeutronRestProxyV2: Unable to update remote port: "
                         "%s"), e.message)
+            raise
 
     def create_subnet(self, context, subnet):
         LOG.debug(_("NeutronRestProxyV2: create_subnet() called"))

neutron/tests/unit/bigswitch/test_restproxy_plugin.py

@@ -43,16 +43,33 @@ class HTTPResponseMock():
         return "{'status': '200 OK'}"
 
 
+class HTTPResponseMock404():
+    status = 404
+    reason = 'Not Found'
+
+    def __init__(self, sock, debuglevel=0, strict=0, method=None,
+                 buffering=False):
+        pass
+
+    def read(self):
+        return "{'status': '404 Not Found'}"
+
+
 class HTTPConnectionMock():
 
     def __init__(self, server, port, timeout):
+        self.response = None
         pass
 
     def request(self, action, uri, body, headers):
+        if uri.endswith('attachment') and action == 'DELETE':
+            self.response = HTTPResponseMock404(None)
+        else:
+            self.response = HTTPResponseMock(None)
         return
 
     def getresponse(self):
-        return HTTPResponseMock(None)
+        return self.response
 
     def close(self):
         pass