Handle deletion of errored instances

When a new instance is created and the state is in error,
the event "compute.instance.create.end" is never sent.

However, when we delete an errored instance the deletion event is
sent, but the entity doesn't exists in te database.

This fix avoid false positives in the critical queue.

Change-Id: I70a4ae92bda37909cfd6021e0311a69b7ad189bc

almanach/collector/handlers/instance_handler.py

@@ -12,7 +12,12 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+from oslo_log import log as logging
+
 from almanach.collector.handlers import base_handler
+from almanach.core import exception
+
+LOG = logging.getLogger(__name__)
 
 
 class InstanceHandler(base_handler.BaseHandler):
@@ -45,7 +50,15 @@ class InstanceHandler(base_handler.BaseHandler):
     def _on_instance_deleted(self, notification):
         date = notification.payload.get("terminated_at")
         instance_id = notification.payload.get("instance_id")
-        self.controller.delete_instance(instance_id, date)
+
+        try:
+            self.controller.delete_instance(instance_id, date)
+        except exception.EntityNotFoundException as e:
+            if notification.payload.get('state') == 'error':
+                LOG.info('Instance deletion event ignored because instance %s was badly created',
+                         instance_id)
+            else:
+                raise e
 
     def _on_instance_resized(self, notification):
         date = notification.context.get("timestamp")

almanach/tests/unit/collector/handlers/test_instance_handler.py

@@ -15,6 +15,7 @@
 import mock
 
 from almanach.collector.handlers import instance_handler
+from almanach.core import exception
 from almanach.tests.unit import base
 from almanach.tests.unit.builders import notification as builder
 
@@ -59,6 +60,37 @@ class TestInstanceHandler(base.BaseTestCase):
             notification.payload['terminated_at']
         )
 
+    def test_instance_deleted_but_never_created(self):
+        notification = builder.InstanceNotificationBuilder() \
+            .with_event_type('compute.instance.delete.end') \
+            .with_payload_value('terminated_at', 'a_date') \
+            .build()
+
+        self.controller.delete_instance.side_effect = exception.EntityNotFoundException('Instance not found')
+
+        self.assertRaises(exception.EntityNotFoundException,
+                          self.instance_handler.handle_events, notification)
+
+        self.controller.delete_instance.assert_called_once_with(
+            notification.payload['instance_id'],
+            notification.payload['terminated_at']
+        )
+
+    def test_instance_in_error_deleted(self):
+        notification = builder.InstanceNotificationBuilder() \
+            .with_event_type('compute.instance.delete.end') \
+            .with_payload_value('terminated_at', 'a_date') \
+            .with_payload_value('state', 'error') \
+            .build()
+
+        self.controller.delete_instance.side_effect = exception.EntityNotFoundException('Instance not found')
+        self.instance_handler.handle_events(notification)
+
+        self.controller.delete_instance.assert_called_once_with(
+            notification.payload['instance_id'],
+            notification.payload['terminated_at']
+        )
+
     def test_instance_resized(self):
         notification = builder.InstanceNotificationBuilder() \
             .with_event_type('compute.instance.resize.confirm.end') \