Merge "Ensure update config function can handle new headers"

src/lib/charm/openstack/mysql_router.py

@@ -635,7 +635,12 @@ class MySQLRouterCharm(charms_openstack.charm.OpenStackCharm):
         config.read(self.mysqlrouter_conf)
         for heading in parameters.keys():
             for param in parameters[heading].keys():
-                config[heading][param] = parameters[heading][param]
+                # BUG LP#1927981 - heading may not exist during a charm upgrade
+                # Handle missing heading via direct assignment in except.
+                try:
+                    config[heading][param] = parameters[heading][param]
+                except KeyError:
+                    config[heading] = {param: parameters[heading][param]}
         ch_core.hookenv.log("Writing {}".format(
             self.mysqlrouter_conf))
         with open(self.mysqlrouter_conf, 'w') as configfile:

unit_tests/test_lib_charm_openstack_mysql_router.py

@@ -661,6 +661,35 @@ class TestMySQLRouterCharm(test_utils.PatchHelper):
         _mock_config_parser.write.assert_called_once_with(
             self.mock_open()().__enter__())
 
+    def test_update_config_parameters_missing_heading(self):
+        # test fix for Bug LP#1927981
+        class FakeConfigParser(dict):
+            def read(*args, **kwargs):
+                pass
+
+            def write(*args, **kwargs):
+                pass
+
+        current_config = {"DEFAULT": {"client_ssl_mode": "NONE"}}
+        fake_config = FakeConfigParser(current_config)
+
+        self.patch_object(mysql_router.configparser, "ConfigParser",
+                          return_value=fake_config)
+
+        # metadata_cache:jujuCluster didn't exist in the previous config so the
+        # header needs to be created (c.f. BUG LP#1927981)
+        _params = {
+            "DEFAULT": {"client_ssl_mode": "PREFERRED"},
+            "metadata_cache:jujuCluster": {"thing": "a-thing"},
+        }
+
+        mrc = mysql_router.MySQLRouterCharm()
+        # should not throw a key error.
+        mrc.update_config_parameters(_params)
+        self.assertIn('metadata_cache:jujuCluster', fake_config)
+        self.assertEqual(fake_config['metadata_cache:jujuCluster'],
+                         {"thing": "a-thing"})
+
     def test_config_changed(self):
         _config_data = {
             "ttl": '5',