From d15244ab4f2562b46c5fbdb6ccebe18f66e5a579 Mon Sep 17 00:00:00 2001
From: Vadim ponomarev <velizarx@gmail.com>
Date: Mon, 12 Feb 2018 16:48:29 +0300
Subject: [PATCH] Fixing the filter in get MTU by network list query.

Based on the observation that a call to sync_routers can be slow
(10-15 seconds for one virtual router), and that profiling data show
that a significant amount of time is spent in function
_get_mtus_by_network_list, this change fixes incorrect the database
query for getting information about networks.

What changed:
- before: SQL query spent time O(#networks in database)
          (select all exists networks from database)
- after : SQL query spent time O(#network_ids passed to the function)
          (select only needed networks)

A basic test shows a drastic improvements, from 2 second to around
~0.2 second, in the processing of a _get_mtus_by_network_list call
with 300 networks in database.

Change-Id: Id50d1aaddd0d2a1110502de9c5b974063daa296a
Closes-Bug: #1748888
---
 neutron/db/l3_db.py                 |  2 +-
 neutron/tests/unit/db/test_l3_db.py | 16 ++++++++++++++++
 2 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/neutron/db/l3_db.py b/neutron/db/l3_db.py
index f5372c0d7c6..d25ec00fa3b 100644
--- a/neutron/db/l3_db.py
+++ b/neutron/db/l3_db.py
@@ -1716,7 +1716,7 @@ class L3_NAT_dbonly_mixin(l3.RouterPluginBase,
     def _get_mtus_by_network_list(self, context, network_ids):
         if not network_ids:
             return {}
-        filters = {'network_id': network_ids}
+        filters = {'id': network_ids}
         fields = ['id', 'mtu']
         networks = self._core_plugin.get_networks(context, filters=filters,
                                                   fields=fields)
diff --git a/neutron/tests/unit/db/test_l3_db.py b/neutron/tests/unit/db/test_l3_db.py
index a24df258130..8e0969f8092 100644
--- a/neutron/tests/unit/db/test_l3_db.py
+++ b/neutron/tests/unit/db/test_l3_db.py
@@ -85,6 +85,22 @@ class TestL3_NAT_dbonly_mixin(base.BaseTestCase):
                 'address_scope_id': mock.sentinel.address_scope_id,
                 'network_id': mock.sentinel.network_id}]}, subnets)
 
+    def test__get_mtus_by_network_list(self):
+        """Basic test that the query get_networks is correctly"""
+        network = {'id': mock.sentinel.network_id,
+                   'name': mock.sentinel.name,
+                   'mtu': mock.sentinel.mtu}
+        with mock.patch.object(directory, 'get_plugin') as get_p:
+            get_p().get_networks.return_value = [network]
+            result = self.db._get_mtus_by_network_list(
+                mock.sentinel.context, [mock.sentinel.network_id])
+            get_p().get_networks.assert_called_once_with(
+                mock.sentinel.context,
+                filters={'id': [mock.sentinel.network_id]},
+                fields=['id', 'mtu'])
+            self.assertEqual({mock.sentinel.network_id: mock.sentinel.mtu},
+                             result)
+
     def test__populate_ports_for_subnets_none(self):
         """Basic test that the method runs correctly with no ports"""
         ports = []