[DBM][Postgres] Adds logical database breakdown for connection metrics

postgres/changelog.d/22999.added

@@ -0,0 +1 @@
+Adds logical database breakdown for connection metrics

postgres/datadog_checks/postgres/util.py

@@ -589,16 +589,23 @@ def trim_leading_set_stmts(sql):
 }
 
 CONNECTION_METRICS = {
-    'descriptors': [],
+    'descriptors': [('database_name', 'db')],
     'metrics': {
         'MAX(setting) AS max_connections': ('max_connections', AgentCheck.gauge),
         'SUM(numbackends)/MAX(setting) AS pct_connections': ('percent_usage_connections', AgentCheck.gauge),
     },
     'relation': False,
     'query': """
-WITH max_con AS (SELECT setting::float FROM pg_settings WHERE name = 'max_connections')
-SELECT {metrics_columns}
-  FROM pg_stat_database, max_con
+WITH max_con AS (
+    SELECT setting::float
+    FROM pg_settings
+    WHERE name = 'max_connections'
+)
+SELECT datname AS database_name
+    , MAX(max_con.setting) AS max_connections
+    , numbackends / MAX(max_con.setting) AS pct_connections
+FROM pg_stat_database, max_con
+GROUP BY datname, numbackends
 """,
     'name': 'connections_metrics',
 }

postgres/tests/common.py

@@ -107,8 +107,8 @@
 
 COMMON_BGW_METRICS_PG_ABOVE_94 = ['postgresql.archiver.archived_count', 'postgresql.archiver.failed_count']
 COMMON_BGW_METRICS_PG_BELOW_17 = ['postgresql.bgwriter.buffers_backend', 'postgresql.bgwriter.buffers_backend_fsync']
-CONNECTION_METRICS = ['postgresql.max_connections', 'postgresql.percent_usage_connections']
-CONNECTION_METRICS_DB = ['postgresql.connections']
+CONNECTION_METRICS = []
+CONNECTION_METRICS_DB = ['postgresql.connections', 'postgresql.max_connections', 'postgresql.percent_usage_connections']
 COMMON_DBS = ['dogs', 'postgres', 'dogs_nofunc', 'dogs_noschema', DB_NAME]
 
 CHECK_PERFORMANCE_METRICS = [

postgres/tests/test_pg_integration.py

@@ -425,10 +425,10 @@ def test_connections_metrics(aggregator, integration_check, pg_instance):
     check.run()
 
     expected_tags = _get_expected_tags(check, pg_instance)
+    expected_tags_with_db = expected_tags + ['db:datadog_test']
     for name in CONNECTION_METRICS:
-        aggregator.assert_metric(name, count=1, tags=expected_tags)
-    expected_tags += ['db:datadog_test']
-    aggregator.assert_metric('postgresql.connections', count=1, tags=expected_tags)
+        aggregator.assert_metric(name, count=1, tags=expected_tags_with_db)
+    aggregator.assert_metric('postgresql.connections', count=1, tags=expected_tags_with_db)
 
 
 @requires_over_10
@@ -809,7 +809,7 @@ def test_correct_hostname(
     check_activity_metrics(aggregator, tags=expected_activity_tags, hostname=expected_hostname)
 
     for name in CONNECTION_METRICS:
-        aggregator.assert_metric(name, count=1, tags=expected_tags_no_db, hostname=expected_hostname)
+        aggregator.assert_metric(name, count=1, tags=expected_tags_with_db, hostname=expected_hostname)
 
     aggregator.assert_service_check(
         'postgres.can_connect',