Decouple ceilometerclient without aodh services running

Currently, the ceilometerclient will be broken if aodh services not
running, it will be worse if users don't want alarming service and they
must start the aodh services.

Change-Id: Idf7468f28cee001262b67b6e110357ffc971535a
Closes-Bug: #1550095

ceilometerclient/tests/unit/test_client.py

@@ -17,6 +17,7 @@ from keystoneclient.auth.identity import v3 as v3_auth
 from keystoneclient import exceptions as ks_exc
 from keystoneclient import session as ks_session
 import mock
+import requests
 
 from ceilometerclient import client
 from ceilometerclient import exc
@@ -218,6 +219,15 @@ class ClientTestWithAodh(ClientTest):
         self.assertEqual('True', (client.alarm_client.http_client.
                                   auth_plugin.opts['insecure']))
 
+    def test_ceilometerclient_available_without_aodh_services_running(self):
+        env = FAKE_ENV.copy()
+        env.pop('auth_plugin', None)
+        with mock.patch('ceilometerclient.openstack.common.apiclient.client.'
+                        'HTTPClient.client_request') as mocked_request:
+            mocked_request.side_effect = requests.exceptions.ConnectionError
+            ceiloclient = client.get_client(2, **env)
+            self.assertIsInstance(ceiloclient, v2client.Client)
+
 
 class ClientAuthTest(utils.BaseTestCase):
 

ceilometerclient/v2/client.py

@@ -16,6 +16,8 @@
 #    under the License.
 import copy
 
+import requests
+
 from ceilometerclient import client as ceiloclient
 from ceilometerclient.v2 import alarms
 from ceilometerclient.v2 import capabilities
@@ -125,3 +127,5 @@ class Client(object):
             return None
         except kc_exc.EndpointNotFound:
             return None
+        except requests.exceptions.ConnectionError:
+            return None