Changes to be committed:

	modified:   cmd/postgres_exporter/postgres_exporter.go
	modified:   cmd/postgres_exporter/queries.go

Added a query to monitor lock clonflicts. Currently used query for locks is showing only number of different locks.
This one is showing number of conflicting locks, which are preventing others from moving forward, with LABEL that contains information about blocking session PID.

Author: heniek

cmd/postgres_exporter/postgres_exporter.go

@@ -225,6 +225,14 @@ var builtinMetricMaps = map[string]intermediateMetricMap{
 		true,
 		0,
 	},
+        "pg_lock_conflicts":{
+                map[string]ColumnMapping{
+                        "blocking_pid": {LABEL, "PID of blocking session", nil, nil},
+			"count": {GAUGE, "Number of blocked sessions", nil, nil},
+                },
+                true,
+                0,
+        },
 	"pg_stat_replication": {
 		map[string]ColumnMapping{
 			"procpid":          {DISCARD, "Process ID of a WAL sender process", nil, semver.MustParseRange("<9.2.0")},

cmd/postgres_exporter/queries.go

@@ -70,7 +70,19 @@ var queryOverrides = map[string][]OverrideQuery{
 			ON tmp.mode=tmp2.mode and pg_database.oid = tmp2.database ORDER BY 1`,
 		},
 	},
-
+  "pg_lock_conflicts": {
+    {
+      semver.MustParseRange(">0.0.0"),
+			`SELECT blockinga.pid AS blocking_pid, count(*) as count
+			FROM pg_catalog.pg_locks blockedl
+			JOIN pg_stat_activity blockeda ON blockedl.pid = blockeda.pid
+			JOIN pg_catalog.pg_locks blockingl ON(blockingl.transactionid=blockedl.transactionid
+			  AND blockedl.pid != blockingl.pid)
+			JOIN pg_stat_activity blockinga ON blockingl.pid = blockinga.pid
+			WHERE NOT blockedl.granted
+			group by blocking_pid`,
+    },
+  },
 	"pg_stat_replication": {
 		{
 			semver.MustParseRange(">=10.0.0"),