Include db tag with postgresql.locks metrics (#2567)

* Include db tag with postgresql.locks metrics

* Fix flake8 complains

* Remove unused ungranted_lock metric

postgres/datadog_checks/postgres/postgres.py

@@ -96,21 +96,23 @@ class PostgreSql(AgentCheck):
     LOCK_METRICS = {
         'descriptors': [
             ('mode', 'lock_mode'),
+            ('datname', 'db'),
             ('relname', 'table'),
         ],
         'metrics': {
             'lock_count': ('postgresql.locks', GAUGE),
-            'ungranted_locks': ('postgresql.ungranted_locks'),
         },
         'query': """
 SELECT mode,
+       pd.datname,
        pc.relname,
        count(*) AS %s
   FROM pg_locks l
+  JOIN pg_database pd ON (l.database = pd.oid)
   JOIN pg_class pc ON (l.relation = pc.oid)
  WHERE l.mode IS NOT NULL
    AND pc.relname NOT LIKE 'pg_%%'
- GROUP BY pc.relname, mode""",
+ GROUP BY pd.datname, pc.relname, mode""",
         'relation': False,
     }
 

postgres/tests/test_common.py

@@ -3,6 +3,7 @@
 # Licensed under Simplified BSD License (see LICENSE)
 import os
 
+import psycopg2
 import pytest
 
 from datadog_checks.postgres import PostgreSql
@@ -122,6 +123,18 @@ def test_connections_metrics(aggregator, check, pg_instance):
     aggregator.assert_metric('postgresql.connections', count=1, tags=pg_instance['tags']+['db:datadog_test'])
 
 
+@pytest.mark.integration
+@pytest.mark.usefixtures('dd_environment')
+def test_locks_metrics(aggregator, check, pg_instance):
+    with psycopg2.connect(host=HOST, dbname=DB_NAME, user="postgres") as conn:
+        with conn.cursor() as cur:
+            cur.execute('LOCK persons')
+            check.check(pg_instance)
+
+    tags = pg_instance['tags'] + ['lock_mode:AccessExclusiveLock', 'table:persons', 'db:datadog_test']
+    aggregator.assert_metric('postgresql.locks', count=1, tags=tags)
+
+
 @pytest.mark.integration
 @pytest.mark.usefixtures('dd_environment')
 def test_activity_metrics(aggregator, check, pg_instance):