Ensure alarm rule conform to alarm type

Threshold_rule or combination_rule must be set to an Alarm object,
and they cannot be set at the same time.
Alarm's type must be one of threshold and combination.
Threshold_rule and combination_rule should be validated according alarm's
type.

Change-Id: I97bf82defeaf0dc1a0e897e10886fd736361041d
Closes-bug: #1288677

ceilometer/api/controllers/v2.py

@@ -1708,17 +1708,8 @@ class Alarm(_Base):
 
     @staticmethod
     def validate(alarm):
-        if (alarm.threshold_rule in (wtypes.Unset, None)
-                and alarm.combination_rule in (wtypes.Unset, None)):
-            error = _("either threshold_rule or combination_rule "
-                      "must be set")
-            raise ClientSideError(error)
-
-        if alarm.threshold_rule and alarm.combination_rule:
-            error = _("threshold_rule and combination_rule "
-                      "cannot be set at the same time")
-            raise ClientSideError(error)
 
+        Alarm.check_rule(alarm)
         if alarm.threshold_rule:
             # ensure an implicit constraint on project_id is added to
             # the query if not already present
@@ -1739,6 +1730,18 @@ class Alarm(_Base):
 
         return alarm
 
+    @staticmethod
+    def check_rule(alarm):
+        rule = '%s_rule' % alarm.type
+        if getattr(alarm, rule) in (wtypes.Unset, None):
+            error = _("%(rule)s must be set for %(type)s"
+                      " type alarm") % {"rule": rule, "type": alarm.type}
+            raise ClientSideError(error)
+        if alarm.threshold_rule and alarm.combination_rule:
+            error = _("threshold_rule and combination_rule "
+                      "cannot be set at the same time")
+            raise ClientSideError(error)
+
     @classmethod
     def sample(cls):
         return cls(alarm_id=None,

ceilometer/tests/api/v2/test_alarm_scenarios.py

@@ -409,9 +409,8 @@ class TestAlarms(FunctionalTest,
         resp = self.post_json('/alarms', params=json, expect_errors=True,
                               status=400, headers=self.auth_headers)
         self.assertEqual(
-            resp.json['error_message']['faultstring'],
-            "either threshold_rule or combination_rule "
-            "must be set")
+            "threshold_rule must be set for threshold type alarm",
+            resp.json['error_message']['faultstring'])
 
     def test_post_invalid_alarm_statistic(self):
         json = {
@@ -930,6 +929,63 @@ class TestAlarms(FunctionalTest,
     def test_post_combination_alarm_as_admin_success_owner_set(self):
         self._do_post_combination_alarm_as_admin_success(True)
 
+    def test_post_combination_alarm_with_threshold_rule(self):
+        """Test the creation of an combination alarm with threshold rule.
+        """
+        json = {
+            'enabled': False,
+            'name': 'added_alarm',
+            'state': 'ok',
+            'type': 'combination',
+            'ok_actions': ['http://something/ok'],
+            'alarm_actions': ['http://something/alarm'],
+            'insufficient_data_actions': ['http://something/no'],
+            'repeat_actions': True,
+            'threshold_rule': {
+                'meter_name': 'ameter',
+                'query': [{'field': 'metadata.field',
+                           'op': 'eq',
+                           'value': '5',
+                           'type': 'string'}],
+                'comparison_operator': 'le',
+                'statistic': 'count',
+                'threshold': 50,
+                'evaluation_periods': '3',
+                'period': '180',
+            }
+        }
+        resp = self.post_json('/alarms', params=json,
+                              expect_errors=True, status=400,
+                              headers=self.auth_headers)
+        self.assertEqual(
+            "combination_rule must be set for combination type alarm",
+            resp.json['error_message']['faultstring'])
+
+    def test_post_threshold_alarm_with_combination_rule(self):
+        """Test the creation of an threshold alarm with combination rule.
+        """
+        json = {
+            'enabled': False,
+            'name': 'added_alarm',
+            'state': 'ok',
+            'type': 'threshold',
+            'ok_actions': ['http://something/ok'],
+            'alarm_actions': ['http://something/alarm'],
+            'insufficient_data_actions': ['http://something/no'],
+            'repeat_actions': True,
+            'combination_rule': {
+                'alarm_ids': ['a',
+                              'b'],
+                'operator': 'and',
+            }
+        }
+        resp = self.post_json('/alarms', params=json,
+                              expect_errors=True, status=400,
+                              headers=self.auth_headers)
+        self.assertEqual(
+            "threshold_rule must be set for threshold type alarm",
+            resp.json['error_message']['faultstring'])
+
     def _do_post_combination_alarm_as_admin_success(self, owner_is_set):
         """Test that post a combination alarm as admin on behalf of nobody
         with an alarm_id of someone else, with owner set or not