prom: Add read quorum per erasure set metric (#18736)

cmd/erasure-server-pool.go

@@ -2296,6 +2296,7 @@ type HealthResult struct {
 		PoolID, SetID int
 		HealthyDrives int
 		HealingDrives int
+		ReadQuorum    int
 		WriteQuorum   int
 	}
 	WriteQuorum   int
@@ -2373,8 +2374,10 @@ func (z *erasureServerPools) Health(ctx context.Context, opts HealthOptions) Hea
 	}
 
 	b := z.BackendInfo()
+	poolReadQuorums := make([]int, len(b.StandardSCData))
 	poolWriteQuorums := make([]int, len(b.StandardSCData))
 	for i, data := range b.StandardSCData {
+		poolReadQuorums[i] = data
 		poolWriteQuorums[i] = data
 		if data == b.StandardSCParity {
 			poolWriteQuorums[i] = data + 1
@@ -2412,15 +2415,17 @@ func (z *erasureServerPools) Health(ctx context.Context, opts HealthOptions) Hea
 	for poolIdx := range erasureSetUpCount {
 		for setIdx := range erasureSetUpCount[poolIdx] {
 			result.ESHealth = append(result.ESHealth, struct {
-				Maintenance                               bool
-				PoolID, SetID                             int
-				HealthyDrives, HealingDrives, WriteQuorum int
+				Maintenance                  bool
+				PoolID, SetID                int
+				HealthyDrives, HealingDrives int
+				ReadQuorum, WriteQuorum      int
 			}{
 				Maintenance:   opts.Maintenance,
 				SetID:         setIdx,
 				PoolID:        poolIdx,
 				HealthyDrives: erasureSetUpCount[poolIdx][setIdx].online,
 				HealingDrives: erasureSetUpCount[poolIdx][setIdx].healing,
+				ReadQuorum:    poolReadQuorums[poolIdx],
 				WriteQuorum:   poolWriteQuorums[poolIdx],
 			})
 

cmd/metrics-v2.go

@@ -3236,6 +3236,16 @@ func getClusterHealthStatusMD() MetricDescription {
 	}
 }
 
+func getClusterErasureSetReadQuorumMD() MetricDescription {
+	return MetricDescription{
+		Namespace: clusterMetricNamespace,
+		Subsystem: "health",
+		Name:      "erasure_set_read_quorum",
+		Help:      "Get the read quorum for this erasure set",
+		Type:      gaugeMetric,
+	}
+}
+
 func getClusterErasureSetWriteQuorumMD() MetricDescription {
 	return MetricDescription{
 		Namespace: clusterMetricNamespace,
@@ -3280,7 +3290,7 @@ func getClusterHealthMetrics() *MetricsGroup {
 		opts := HealthOptions{}
 		result := objLayer.Health(ctx, opts)
 
-		metrics = make([]Metric, 0, 2+3*len(result.ESHealth))
+		metrics = make([]Metric, 0, 2+4*len(result.ESHealth))
 
 		metrics = append(metrics, Metric{
 			Description: getClusterWriteQuorumMD(),
@@ -3302,6 +3312,11 @@ func getClusterHealthMetrics() *MetricsGroup {
 				"pool": strconv.Itoa(h.PoolID),
 				"set":  strconv.Itoa(h.SetID),
 			}
+			metrics = append(metrics, Metric{
+				Description:    getClusterErasureSetReadQuorumMD(),
+				VariableLabels: labels,
+				Value:          float64(h.ReadQuorum),
+			})
 			metrics = append(metrics, Metric{
 				Description:    getClusterErasureSetWriteQuorumMD(),
 				VariableLabels: labels,