Merge pull request #70 from universalcore/feature/issue-68-tasks-404-12x

Check for 404 during task syncing

consular/main.py

@@ -529,7 +529,15 @@ def _consul_key_to_marathon_label_key(self, consul_key):
 
     @inlineCallbacks
     def sync_app_tasks(self, app):
-        tasks = yield self.marathon_client.get_app_tasks(app['id'])
+        tasks = yield handle_not_found_error(
+            self.marathon_client.get_app_tasks, app['id'])
+        if tasks is None:
+            # Certain versions of Marathon may return 404 when an app has no
+            # tasks. Other versions return an empty list.
+            # https://github.com/mesosphere/marathon/issues/3881
+            log.msg('No tasks found in Marathon for app ID "%s"' % app['id'])
+            return
+
         for task in tasks:
             yield self.register_task_service(
                 app['id'], task['id'], task['host'], task['ports'])

consular/tests/test_main.py

@@ -736,6 +736,31 @@ def test_sync_app_tasks_multiple_ports(self):
             FakeResponse(200, [], json.dumps({})))
         yield d
 
+    @inlineCallbacks
+    def test_sync_app_tasks_not_found(self):
+        """
+        When syncing an app with a task, and Marathon has no tasks for the app,
+        Consular should handle a 404 response from Marathon gracefully.
+        """
+        d = self.consular.sync_app_tasks({'id': '/my-app'})
+
+        # First Consular fetches the tasks for the app
+        marathon_request = yield self.requests.get()
+        self.assertEqual(marathon_request['method'], 'GET')
+        self.assertEqual(
+            marathon_request['url'],
+            'http://localhost:8080/v2/apps/my-app/tasks')
+
+        # Respond with a 404
+        marathon_request['deferred'].callback(
+            FakeResponse(404, [], json.dumps(
+                {"message": "App '/my-app' does not exist"}))
+        )
+
+        # Nothing much should happen -- there are no tasks
+
+        yield d
+
     @inlineCallbacks
     def test_sync_app_labels(self):
         app = {