Fix for Postgres max connections. Postgres does not limit connections by database, but total over the server. Additionally, alert labels didn't match across the pair. Using a min by on the right side deals with the possibility additional labels are present on your exporter. (#376)

_data/rules.yml

@@ -619,7 +619,7 @@ groups:
                 severity: warning
               - name: Postgresql too many connections
                 description: PostgreSQL instance has too many connections (> 80%).
-                query: 'sum by (datname) (pg_stat_activity_count{datname!~"template.*|postgres"}) > pg_settings_max_connections * 0.8'
+                expr: 'sum by (instance, job, server) (pg_stat_activity_count) > min by (instance, job, server) (pg_settings_max_connections * 0.8)'
                 severity: warning
                 for: 2m
               - name: Postgresql not enough connections

dist/rules/postgresql/postgres-exporter.yml

@@ -50,7 +50,7 @@ groups:
         description: "Table {{ $labels.relname }} has not been auto analyzed for 10 days\n  VALUE = {{ $value }}\n  LABELS = {{ $labels }}"
 
     - alert: PostgresqlTooManyConnections
-      expr: 'sum by (datname) (pg_stat_activity_count{datname!~"template.*|postgres"}) > pg_settings_max_connections * 0.8'
+      expr: 'sum by (instance, job, server) (pg_stat_activity_count) > min by (instance, job, server) (pg_settings_max_connections * 0.8)'
       for: 2m
       labels:
         severity: warning