Add missing DB size metric (#157)

* Add missing dashboard metrics

* cache query for 30 seconds

* Cast bool to string

* Will have to handle pg_replication at different time

Author: davissp14

cmd/start/main.go

@@ -74,6 +74,7 @@ func main() {
 		"DATA_SOURCE_PASS":                    node.SUCredentials.Password,
 		"PG_EXPORTER_EXCLUDE_DATABASE":        "template0,template1",
 		"PG_EXPORTER_AUTO_DISCOVER_DATABASES": "true",
+		"PG_EXPORTER_EXTEND_QUERY_PATH":       "/fly/queries.yaml",
 	}
 	svisor.AddProcess("exporter", "postgres_exporter --log.level=warn ",
 		supervisor.WithEnv(exporterEnv),

config/queries.yaml

@@ -9,3 +9,18 @@ pg_database:
     - size_bytes:
         usage: "GAUGE"
         description: "Disk space used by the database"
+
+# pg_replication:
+#   query: "SELECT slot_name, CAST(active AS TEXT), pg_wal_lsn_diff(pg_current_wal_lsn(), restart_lsn) AS lag FROM pg_replication_slots"
+#   master: true
+#   cache_seconds: 30
+#   metrics:
+#     - slot_name:
+#         usage: "LABEL"
+#         description: "Name of replication slot"
+#     # - active:
+#     #     usage: "LABEL"
+#     #     description: "Whether the replication slot is active"
+#     - lag:
+#         usage: "GAUGE"
+#         description: "Replication lag in bytes"