From 3b7781835e706a9f09bde96e20082167edbea613 Mon Sep 17 00:00:00 2001
From: Harshavardhana <harsha@minio.io>
Date: Mon, 3 Apr 2023 21:23:24 -0700
Subject: [PATCH] add lock metrics per node (#16943)

---
 cmd/local-locker.go | 29 ++++++++++++++++++++++++
 cmd/metrics-v2.go   | 54 +++++++++++++++++++++++++++++++++++++++++++--
 2 files changed, 81 insertions(+), 2 deletions(-)

diff --git a/cmd/local-locker.go b/cmd/local-locker.go
index c6e9a3ffb..dd609e759 100644
--- a/cmd/local-locker.go
+++ b/cmd/local-locker.go
@@ -213,12 +213,41 @@ func (l *localLocker) RUnlock(_ context.Context, args dsync.LockArgs) (reply boo
 	return reply, nil
 }
 
+type lockStats struct {
+	Total  int
+	Writes int
+	Reads  int
+}
+
+func (l *localLocker) stats() lockStats {
+	l.mutex.Lock()
+	defer l.mutex.Unlock()
+
+	st := lockStats{Total: len(l.lockMap)}
+	for _, v := range l.lockMap {
+		if len(v) == 0 {
+			continue
+		}
+		entry := v[0]
+		if entry.Writer {
+			st.Writes++
+		} else {
+			st.Reads += len(v)
+		}
+	}
+	return st
+}
+
 func (l *localLocker) DupLockMap() map[string][]lockRequesterInfo {
 	l.mutex.Lock()
 	defer l.mutex.Unlock()
 
 	lockCopy := make(map[string][]lockRequesterInfo, len(l.lockMap))
 	for k, v := range l.lockMap {
+		if len(v) == 0 {
+			delete(l.lockMap, k)
+			continue
+		}
 		lockCopy[k] = append(make([]lockRequesterInfo, 0, len(v)), v...)
 	}
 	return lockCopy
diff --git a/cmd/metrics-v2.go b/cmd/metrics-v2.go
index b9d50609e..8331c5e94 100644
--- a/cmd/metrics-v2.go
+++ b/cmd/metrics-v2.go
@@ -77,7 +77,7 @@ func init() {
 		return allMetrics
 	}()
 
-	nodeCollector = newMinioCollectorNode([]*MetricsGroup{
+	nodeGroups := []*MetricsGroup{
 		getNodeHealthMetrics(),
 		getLocalDriveStorageMetrics(),
 		getCacheMetrics(),
@@ -86,7 +86,10 @@ func init() {
 		getMinioVersionMetrics(),
 		getS3TTFBMetric(),
 		getNotificationMetrics(),
-	})
+		getDistLockMetrics(),
+	}
+
+	nodeCollector = newMinioCollectorNode(nodeGroups)
 	clusterCollector = newMinioClusterCollector(allMetricsGroups)
 }
 
@@ -1663,6 +1666,53 @@ func getCacheMetrics() *MetricsGroup {
 	return mg
 }
 
+func getDistLockMetrics() *MetricsGroup {
+	mg := &MetricsGroup{
+		cacheInterval: 1 * time.Second,
+	}
+	mg.RegisterRead(func(ctx context.Context) []Metric {
+		if !globalIsDistErasure {
+			return []Metric{}
+		}
+
+		st := globalLockServer.stats()
+
+		metrics := make([]Metric, 0, 3)
+		metrics = append(metrics, Metric{
+			Description: MetricDescription{
+				Namespace: minioNamespace,
+				Subsystem: "locks",
+				Name:      "total",
+				Help:      "Number of current locks on this peer",
+				Type:      gaugeMetric,
+			},
+			Value: float64(st.Total),
+		})
+		metrics = append(metrics, Metric{
+			Description: MetricDescription{
+				Namespace: minioNamespace,
+				Subsystem: "locks",
+				Name:      "write_total",
+				Help:      "Number of current WRITE locks on this peer",
+				Type:      gaugeMetric,
+			},
+			Value: float64(st.Writes),
+		})
+		metrics = append(metrics, Metric{
+			Description: MetricDescription{
+				Namespace: minioNamespace,
+				Subsystem: "locks",
+				Name:      "read_total",
+				Help:      "Number of current READ locks on this peer",
+				Type:      gaugeMetric,
+			},
+			Value: float64(st.Reads),
+		})
+		return metrics
+	})
+	return mg
+}
+
 func getNotificationMetrics() *MetricsGroup {
 	mg := &MetricsGroup{
 		cacheInterval: 10 * time.Second,