Correct the order when sorting by "severity"

Related to change[1], since we have supported pagination query now, we
need to also fix the ordering of 'severity' in listing alarms.

[1] I69531e3b53a11026a35a40a415f48b7bb838010b

Change-Id: Icb5239f1c4a5ef1e7e5733bc440eed12bb2f5b9f
Related-Bug: #1452254

aodh/storage/impl_sqlalchemy.py

@@ -25,6 +25,9 @@ from oslo_db.sqlalchemy import utils as oslo_sql_utils
 from oslo_log import log
 from oslo_utils import timeutils
 import six
+from sqlalchemy import asc
+from sqlalchemy import desc
+from sqlalchemy import func
 from sqlalchemy.orm import exc
 
 from aodh.i18n import _LI
@@ -161,6 +164,16 @@ class Connection(base.Connection):
                 raise storage.InvalidMarker(
                     'Marker %s not found.' % pagination['marker'])
         limit = pagination.get('limit')
+        # we sort by "severity" by its semantic than its alphabetical
+        # order when "severity" specified in sorts.
+        for sort_key, sort_dir in pagination['sort'][::-1]:
+            if sort_key == 'severity':
+                sort_dir_func = {'asc': asc, 'desc': desc}[sort_dir]
+                query = query.order_by(sort_dir_func(
+                    func.field(getattr(model, sort_key), 'low',
+                               'moderate', 'critical')))
+                pagination['sort'].remove((sort_key, sort_dir))
+
         sort_keys = [s[0] for s in pagination['sort']]
         sort_dirs = [s[1] for s in pagination['sort']]
         return oslo_sql_utils.paginate_query(

aodh/tests/functional/api/v2/test_alarm_scenarios.py

@@ -3313,6 +3313,18 @@ class TestPaginationQuery(TestAlarmsBase):
         names = [a['name'] for a in data]
         self.assertEqual(['name1', 'name2', 'name3', 'name4'], names)
 
+    def test_sort_by_severity_with_its_value(self):
+        data = self.get_json('/alarms?sort=severity:asc',
+                             headers=self.auth_headers)
+        severities = [a['severity'] for a in data]
+        self.assertEqual(['low', 'moderate', 'critical', 'critical'],
+                         severities)
+        data = self.get_json('/alarms?sort=severity:desc',
+                             headers=self.auth_headers)
+        severities = [a['severity'] for a in data]
+        self.assertEqual(['critical', 'critical', 'moderate', 'low'],
+                         severities)
+
     def test_pagination_query_limit(self):
         data = self.get_json('/alarms?limit=2',  headers=self.auth_headers)
         self.assertEqual(2, len(data))