Disable specifying alarm itself in combination rule

Currently, update combination alarm can specify itself in alarm_ids,
however, that will cause endless loop when evaluating this alarm.

This patch adds a check to disable such behavior.

Change-Id: I63b465c59fe39206ae04b0736482d1ffd7bf59c4
Closes-Bug: #1304419
(cherry picked from commit de8176fa73)

ceilometer/api/controllers/v2.py

@@ -1925,6 +1925,13 @@ class AlarmController(rest.RestController):
                     _("Alarm with name=%s exists") % data.name,
                     status_code=409)
 
+        # should check if there is any circle in the dependency, but for
+        # efficiency reason, here only check alarm cannot depend on itself
+        if data.type == 'combination':
+            if self._id in data.combination_rule.alarm_ids:
+                raise ClientSideError(_('Cannot specify alarm %s itself in '
+                                        'combination rule') % self._id)
+
         old_alarm = Alarm.from_db_model(alarm_in).as_dict(storage.models.Alarm)
         updated_alarm = data.as_dict(storage.models.Alarm)
         try:

ceilometer/tests/api/v2/test_alarm_scenarios.py

@@ -1344,6 +1344,30 @@ class TestAlarms(FunctionalTest,
             'Alarm with name=name1 exists',
             resp.json['error_message']['faultstring'])
 
+    def test_put_alarm_combination_cannot_specify_itself(self):
+        json = {
+            'name': 'name4',
+            'type': 'combination',
+            'combination_rule': {
+                'alarm_ids': ['d'],
+            }
+        }
+
+        data = self.get_json('/alarms',
+                             q=[{'field': 'name',
+                                 'value': 'name4',
+                                 }])
+        self.assertEqual(1, len(data))
+        alarm_id = data[0]['alarm_id']
+
+        resp = self.put_json('/alarms/%s' % alarm_id,
+                             expect_errors=True, status=400,
+                             params=json,
+                             headers=self.auth_headers)
+
+        msg = 'Cannot specify alarm %s itself in combination rule' % alarm_id
+        self.assertEqual(msg, resp.json['error_message']['faultstring'])
+
     def test_delete_alarm(self):
         data = self.get_json('/alarms')
         self.assertEqual(4, len(data))