lock conflicts monitoring (#111)

Author: ritbl

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"),