Catch PortNotFound and SubnetNotFound during network_delete

In some cases PortNotFound exception during network_delete
could be caused by concurrent port deletion by DHCP agent.
This condition should not prevent network from deleting.

(cherry picked from 8479921e11)

Change-Id: Ie6eae4cecb64120c41de9823d9e72066094ad2ce
Closes-Bug: #1405197

neutron/plugins/ml2/plugin.py

@@ -561,6 +561,31 @@ class Ml2Plugin(db_base_plugin_v2.NeutronDbPluginV2,
 
         return [self._fields(net, fields) for net in nets]
 
+    def _delete_ports(self, context, ports):
+        for port in ports:
+            try:
+                self.delete_port(context, port.id)
+            except exc.PortNotFound:
+                # concurrent port deletion can be performed by
+                # release_dhcp_port caused by concurrent subnet_delete
+                LOG.info(_("Port %s was deleted concurrently"), port.id)
+            except Exception:
+                with excutils.save_and_reraise_exception():
+                    LOG.exception(_("Exception auto-deleting port %s"),
+                                  port.id)
+
+    def _delete_subnets(self, context, subnets):
+        for subnet in subnets:
+            try:
+                self.delete_subnet(context, subnet.id)
+            except exc.SubnetNotFound:
+                LOG.info(_("Subnet %s was deleted concurrently"),
+                         subnet.id)
+            except Exception:
+                with excutils.save_and_reraise_exception():
+                    LOG.exception(_("Exception auto-deleting subnet %s"),
+                                  subnet.id)
+
     def delete_network(self, context, id):
         # REVISIT(rkukura) The super(Ml2Plugin, self).delete_network()
         # function is not used because it auto-deletes ports and
@@ -636,22 +661,8 @@ class Ml2Plugin(db_base_plugin_v2.NeutronDbPluginV2,
                         msg = _("A concurrent port creation has occurred")
                         LOG.warning(msg)
                         continue
-
-            for port in ports:
-                try:
-                    self.delete_port(context, port.id)
-                except Exception:
-                    with excutils.save_and_reraise_exception():
-                        LOG.exception(_("Exception auto-deleting port %s"),
-                                      port.id)
-
-            for subnet in subnets:
-                try:
-                    self.delete_subnet(context, subnet.id)
-                except Exception:
-                    with excutils.save_and_reraise_exception():
-                        LOG.exception(_("Exception auto-deleting subnet %s"),
-                                      subnet.id)
+            self._delete_ports(context, ports)
+            self._delete_subnets(context, subnets)
 
         try:
             self.mechanism_manager.delete_network_postcommit(mech_context)

neutron/tests/unit/ml2/test_ml2_plugin.py

@@ -117,7 +117,17 @@ class TestMl2V2HTTPResponse(test_plugin.TestV2HTTPResponse,
 
 class TestMl2NetworksV2(test_plugin.TestNetworksV2,
                         Ml2PluginV2TestCase):
-    pass
+    def test_port_delete_helper_tolerates_failure(self):
+        plugin = manager.NeutronManager.get_plugin()
+        with mock.patch.object(plugin, "delete_port",
+                               side_effect=exc.PortNotFound(port_id="123")):
+            plugin._delete_ports(None, [mock.MagicMock()])
+
+    def test_subnet_delete_helper_tolerates_failure(self):
+        plugin = manager.NeutronManager.get_plugin()
+        with mock.patch.object(plugin, "delete_subnet",
+                               side_effect=exc.SubnetNotFound(subnet_id="1")):
+            plugin._delete_subnets(None, [mock.MagicMock()])
 
 
 class TestMl2SubnetsV2(test_plugin.TestSubnetsV2,