Fix uninitialized replication stats (#20260)

Services are unfrozen before `initBackgroundReplication` is finished. This means that 
the globalReplicationStats write is racy. Switch to an atomic pointer.

Provide the `ReplicationPool` with the stats, so it doesn't have to be grabbed 
from the atomic pointer on every use.

All other loads and checks are nil, and calls return empty values when stats 
still haven't been initialized.

cmd/bucket-handlers.go

@@ -1682,7 +1682,7 @@ func (api objectAPIHandlers) DeleteBucketHandler(w http.ResponseWriter, r *http.
 	}
 
 	globalNotificationSys.DeleteBucketMetadata(ctx, bucket)
-	globalReplicationPool.deleteResyncMetadata(ctx, bucket)
+	globalReplicationPool.Get().deleteResyncMetadata(ctx, bucket)
 
 	// Call site replication hook.
 	replLogIf(ctx, globalSiteReplicationSys.DeleteBucketHook(ctx, bucket, forceDelete))

cmd/bucket-replication-handlers.go

@@ -230,7 +230,7 @@ func (api objectAPIHandlers) GetBucketReplicationMetricsHandler(w http.ResponseW
 	w.Header().Set(xhttp.ContentType, string(mimeJSON))
 
 	enc := json.NewEncoder(w)
-	stats := globalReplicationStats.getLatestReplicationStats(bucket)
+	stats := globalReplicationStats.Load().getLatestReplicationStats(bucket)
 	bwRpt := globalNotificationSys.GetBandwidthReports(ctx, bucket)
 	bwMap := bwRpt.BucketStats
 	for arn, st := range stats.ReplicationStats.Stats {
@@ -286,7 +286,7 @@ func (api objectAPIHandlers) GetBucketReplicationMetricsV2Handler(w http.Respons
 	w.Header().Set(xhttp.ContentType, string(mimeJSON))
 
 	enc := json.NewEncoder(w)
-	stats := globalReplicationStats.getLatestReplicationStats(bucket)
+	stats := globalReplicationStats.Load().getLatestReplicationStats(bucket)
 	bwRpt := globalNotificationSys.GetBandwidthReports(ctx, bucket)
 	bwMap := bwRpt.BucketStats
 	for arn, st := range stats.ReplicationStats.Stats {
@@ -422,7 +422,7 @@ func (api objectAPIHandlers) ResetBucketReplicationStartHandler(w http.ResponseW
 		return
 	}
 
-	if err := globalReplicationPool.resyncer.start(ctx, objectAPI, resyncOpts{
+	if err := globalReplicationPool.Get().resyncer.start(ctx, objectAPI, resyncOpts{
 		bucket:       bucket,
 		arn:          arn,
 		resyncID:     resetID,

cmd/bucket-replication-metrics.go

@@ -119,7 +119,7 @@ func (a *ActiveWorkerStat) update() {
 	if a == nil {
 		return
 	}
-	a.Curr = globalReplicationPool.ActiveWorkers()
+	a.Curr = globalReplicationPool.Get().ActiveWorkers()
 	a.hist.Update(int64(a.Curr))
 	a.Avg = float32(a.hist.Mean())
 	a.Max = int(a.hist.Max())

cmd/bucket-replication-stats.go

@@ -87,6 +87,9 @@ func (r *ReplicationStats) updateMovingAvg() {
 
 // ActiveWorkers returns worker stats
 func (r *ReplicationStats) ActiveWorkers() ActiveWorkerStat {
+	if r == nil {
+		return ActiveWorkerStat{}
+	}
 	r.wlock.RLock()
 	defer r.wlock.RUnlock()
 	w := r.workers.get()
@@ -351,6 +354,9 @@ func NewReplicationStats(ctx context.Context, objectAPI ObjectLayer) *Replicatio
 }
 
 func (r *ReplicationStats) getAllLatest(bucketsUsage map[string]BucketUsageInfo) (bucketsReplicationStats map[string]BucketStats) {
+	if r == nil {
+		return nil
+	}
 	peerBucketStatsList := globalNotificationSys.GetClusterAllBucketStats(GlobalContext)
 	bucketsReplicationStats = make(map[string]BucketStats, len(bucketsUsage))
 
@@ -460,6 +466,9 @@ func (r *ReplicationStats) calculateBucketReplicationStats(bucket string, bucket
 
 // get the most current of in-memory replication stats  and data usage info from crawler.
 func (r *ReplicationStats) getLatestReplicationStats(bucket string) (s BucketStats) {
+	if r == nil {
+		return s
+	}
 	bucketStats := globalNotificationSys.GetClusterBucketStats(GlobalContext, bucket)
 	return r.calculateBucketReplicationStats(bucket, bucketStats)
 }
@@ -495,9 +504,14 @@ func (r *ReplicationStats) decQ(bucket string, sz int64, isDelMarker bool, opTyp
 
 // incProxy increments proxy metrics for proxied calls
 func (r *ReplicationStats) incProxy(bucket string, api replProxyAPI, isErr bool) {
+	if r != nil {
 		r.pCache.inc(bucket, api, isErr)
+	}
 }
 
 func (r *ReplicationStats) getProxyStats(bucket string) ProxyMetric {
+	if r == nil {
+		return ProxyMetric{}
+	}
 	return r.pCache.getBucketStats(bucket)
 }

cmd/bucket-replication.go

@@ -50,6 +50,7 @@ import (
 	xhttp "github.com/minio/minio/internal/http"
 	xioutil "github.com/minio/minio/internal/ioutil"
 	"github.com/minio/minio/internal/logger"
+	"github.com/minio/minio/internal/once"
 	"github.com/tinylib/msgp/msgp"
 	"github.com/zeebo/xxh3"
 	"golang.org/x/exp/maps"
@@ -478,7 +479,7 @@ func replicateDelete(ctx context.Context, dobj DeletedObjectReplicationInfo, obj
 	lk := objectAPI.NewNSLock(bucket, "/[replicate]/"+dobj.ObjectName)
 	lkctx, err := lk.GetLock(ctx, globalOperationTimeout)
 	if err != nil {
-		globalReplicationPool.queueMRFSave(dobj.ToMRFEntry())
+		globalReplicationPool.Get().queueMRFSave(dobj.ToMRFEntry())
 		sendEvent(eventArgs{
 			BucketName: bucket,
 			Object: ObjectInfo{
@@ -548,7 +549,7 @@ func replicateDelete(ctx context.Context, dobj DeletedObjectReplicationInfo, obj
 	// to decrement pending count later.
 	for _, rinfo := range rinfos.Targets {
 		if rinfo.ReplicationStatus != rinfo.PrevReplicationStatus {
-			globalReplicationStats.Update(dobj.Bucket, rinfo, replicationStatus,
+			globalReplicationStats.Load().Update(dobj.Bucket, rinfo, replicationStatus,
 				prevStatus)
 		}
 	}
@@ -556,7 +557,7 @@ func replicateDelete(ctx context.Context, dobj DeletedObjectReplicationInfo, obj
 	eventName := event.ObjectReplicationComplete
 	if replicationStatus == replication.Failed {
 		eventName = event.ObjectReplicationFailed
-		globalReplicationPool.queueMRFSave(dobj.ToMRFEntry())
+		globalReplicationPool.Get().queueMRFSave(dobj.ToMRFEntry())
 	}
 	drs := getReplicationState(rinfos, dobj.ReplicationState, dobj.VersionID)
 	if replicationStatus != prevStatus {
@@ -1054,7 +1055,7 @@ func replicateObject(ctx context.Context, ri ReplicateObjectInfo, objectAPI Obje
 			UserAgent:  "Internal: [Replication]",
 			Host:       globalLocalNodeName,
 		})
-		globalReplicationPool.queueMRFSave(ri.ToMRFEntry())
+		globalReplicationPool.Get().queueMRFSave(ri.ToMRFEntry())
 		return
 	}
 	ctx = lkctx.Context()
@@ -1139,7 +1140,7 @@ func replicateObject(ctx context.Context, ri ReplicateObjectInfo, objectAPI Obje
 		for _, rinfo := range rinfos.Targets {
 			if rinfo.ReplicationStatus != rinfo.PrevReplicationStatus {
 				rinfo.OpType = opType // update optype to reflect correct operation.
-				globalReplicationStats.Update(bucket, rinfo, rinfo.ReplicationStatus, rinfo.PrevReplicationStatus)
+				globalReplicationStats.Load().Update(bucket, rinfo, rinfo.ReplicationStatus, rinfo.PrevReplicationStatus)
 			}
 		}
 	}
@@ -1159,7 +1160,7 @@ func replicateObject(ctx context.Context, ri ReplicateObjectInfo, objectAPI Obje
 		ri.EventType = ReplicateMRF
 		ri.ReplicationStatusInternal = rinfos.ReplicationStatusInternal()
 		ri.RetryCount++
-		globalReplicationPool.queueMRFSave(ri.ToMRFEntry())
+		globalReplicationPool.Get().queueMRFSave(ri.ToMRFEntry())
 	}
 }
 
@@ -1787,8 +1788,8 @@ const (
 )
 
 var (
-	globalReplicationPool  *ReplicationPool
+	globalReplicationPool  = once.NewSingleton[ReplicationPool]()
-	globalReplicationStats *ReplicationStats
+	globalReplicationStats atomic.Pointer[ReplicationStats]
 )
 
 // ReplicationPool describes replication pool
@@ -1803,6 +1804,7 @@ type ReplicationPool struct {
 	priority    string
 	maxWorkers  int
 	maxLWorkers int
+	stats       *ReplicationStats
 
 	mu       sync.RWMutex
 	mrfMU    sync.Mutex
@@ -1849,7 +1851,7 @@ const (
 )
 
 // NewReplicationPool creates a pool of replication workers of specified size
-func NewReplicationPool(ctx context.Context, o ObjectLayer, opts replicationPoolOpts) *ReplicationPool {
+func NewReplicationPool(ctx context.Context, o ObjectLayer, opts replicationPoolOpts, stats *ReplicationStats) *ReplicationPool {
 	var workers, failedWorkers int
 	priority := "auto"
 	maxWorkers := WorkerMaxLimit
@@ -1891,6 +1893,7 @@ func NewReplicationPool(ctx context.Context, o ObjectLayer, opts replicationPool
 		mrfStopCh:       make(chan struct{}, 1),
 		ctx:             ctx,
 		objLayer:        o,
+		stats:           stats,
 		priority:        priority,
 		maxWorkers:      maxWorkers,
 		maxLWorkers:     maxLWorkers,
@@ -1918,11 +1921,11 @@ func (p *ReplicationPool) AddMRFWorker() {
 			}
 			switch v := oi.(type) {
 			case ReplicateObjectInfo:
-				globalReplicationStats.incQ(v.Bucket, v.Size, v.DeleteMarker, v.OpType)
+				p.stats.incQ(v.Bucket, v.Size, v.DeleteMarker, v.OpType)
 				atomic.AddInt32(&p.activeMRFWorkers, 1)
 				replicateObject(p.ctx, v, p.objLayer)
 				atomic.AddInt32(&p.activeMRFWorkers, -1)
-				globalReplicationStats.decQ(v.Bucket, v.Size, v.DeleteMarker, v.OpType)
+				p.stats.decQ(v.Bucket, v.Size, v.DeleteMarker, v.OpType)
 
 			default:
 				bugLogIf(p.ctx, fmt.Errorf("unknown mrf replication type: %T", oi), "unknown-mrf-replicate-type")
@@ -1950,9 +1953,9 @@ func (p *ReplicationPool) AddWorker(input <-chan ReplicationWorkerOperation, opT
 				if opTracker != nil {
 					atomic.AddInt32(opTracker, 1)
 				}
-				globalReplicationStats.incQ(v.Bucket, v.Size, v.DeleteMarker, v.OpType)
+				p.stats.incQ(v.Bucket, v.Size, v.DeleteMarker, v.OpType)
 				replicateObject(p.ctx, v, p.objLayer)
-				globalReplicationStats.decQ(v.Bucket, v.Size, v.DeleteMarker, v.OpType)
+				p.stats.decQ(v.Bucket, v.Size, v.DeleteMarker, v.OpType)
 				if opTracker != nil {
 					atomic.AddInt32(opTracker, -1)
 				}
@@ -1960,10 +1963,10 @@ func (p *ReplicationPool) AddWorker(input <-chan ReplicationWorkerOperation, opT
 				if opTracker != nil {
 					atomic.AddInt32(opTracker, 1)
 				}
-				globalReplicationStats.incQ(v.Bucket, 0, true, v.OpType)
+				p.stats.incQ(v.Bucket, 0, true, v.OpType)
 
 				replicateDelete(p.ctx, v, p.objLayer)
-				globalReplicationStats.decQ(v.Bucket, 0, true, v.OpType)
+				p.stats.decQ(v.Bucket, 0, true, v.OpType)
 
 				if opTracker != nil {
 					atomic.AddInt32(opTracker, -1)
@@ -1990,9 +1993,9 @@ func (p *ReplicationPool) AddLargeWorker(input <-chan ReplicationWorkerOperation
 				if opTracker != nil {
 					atomic.AddInt32(opTracker, 1)
 				}
-				globalReplicationStats.incQ(v.Bucket, v.Size, v.DeleteMarker, v.OpType)
+				p.stats.incQ(v.Bucket, v.Size, v.DeleteMarker, v.OpType)
 				replicateObject(p.ctx, v, p.objLayer)
-				globalReplicationStats.decQ(v.Bucket, v.Size, v.DeleteMarker, v.OpType)
+				p.stats.decQ(v.Bucket, v.Size, v.DeleteMarker, v.OpType)
 				if opTracker != nil {
 					atomic.AddInt32(opTracker, -1)
 				}
@@ -2156,7 +2159,7 @@ func (p *ReplicationPool) queueReplicaTask(ri ReplicateObjectInfo) {
 		case <-p.ctx.Done():
 		case p.lrgworkers[h%uint64(len(p.lrgworkers))] <- ri:
 		default:
-			globalReplicationPool.queueMRFSave(ri.ToMRFEntry())
+			p.queueMRFSave(ri.ToMRFEntry())
 			p.mu.RLock()
 			maxLWorkers := p.maxLWorkers
 			existing := len(p.lrgworkers)
@@ -2187,7 +2190,7 @@ func (p *ReplicationPool) queueReplicaTask(ri ReplicateObjectInfo) {
 	case healCh <- ri:
 	case ch <- ri:
 	default:
-		globalReplicationPool.queueMRFSave(ri.ToMRFEntry())
+		globalReplicationPool.Get().queueMRFSave(ri.ToMRFEntry())
 		p.mu.RLock()
 		prio := p.priority
 		maxWorkers := p.maxWorkers
@@ -2223,7 +2226,7 @@ func queueReplicateDeletesWrapper(doi DeletedObjectReplicationInfo, existingObje
 			doi.ResetID = v.ResetID
 			doi.TargetArn = k
 
-			globalReplicationPool.queueReplicaDeleteTask(doi)
+			globalReplicationPool.Get().queueReplicaDeleteTask(doi)
 		}
 	}
 }
@@ -2244,7 +2247,7 @@ func (p *ReplicationPool) queueReplicaDeleteTask(doi DeletedObjectReplicationInf
 	case <-p.ctx.Done():
 	case ch <- doi:
 	default:
-		globalReplicationPool.queueMRFSave(doi.ToMRFEntry())
+		p.queueMRFSave(doi.ToMRFEntry())
 		p.mu.RLock()
 		prio := p.priority
 		maxWorkers := p.maxWorkers
@@ -2274,9 +2277,10 @@ type replicationPoolOpts struct {
 }
 
 func initBackgroundReplication(ctx context.Context, objectAPI ObjectLayer) {
-	globalReplicationPool = NewReplicationPool(ctx, objectAPI, globalAPIConfig.getReplicationOpts())
+	stats := NewReplicationStats(ctx, objectAPI)
-	globalReplicationStats = NewReplicationStats(ctx, objectAPI)
+	globalReplicationPool.Set(NewReplicationPool(ctx, objectAPI, globalAPIConfig.getReplicationOpts(), stats))
-	go globalReplicationStats.trackEWMA()
+	globalReplicationStats.Store(stats)
+	go stats.trackEWMA()
 }
 
 type proxyResult struct {
@@ -2482,7 +2486,7 @@ func scheduleReplication(ctx context.Context, oi ObjectInfo, o ObjectLayer, dsc
 	if dsc.Synchronous() {
 		replicateObject(ctx, ri, o)
 	} else {
-		globalReplicationPool.queueReplicaTask(ri)
+		globalReplicationPool.Get().queueReplicaTask(ri)
 	}
 }
 
@@ -2610,9 +2614,9 @@ func proxyGetTaggingToRepTarget(ctx context.Context, bucket, object string, opts
 }
 
 func scheduleReplicationDelete(ctx context.Context, dv DeletedObjectReplicationInfo, o ObjectLayer) {
-	globalReplicationPool.queueReplicaDeleteTask(dv)
+	globalReplicationPool.Get().queueReplicaDeleteTask(dv)
 	for arn := range dv.ReplicationState.Targets {
-		globalReplicationStats.Update(dv.Bucket, replicatedTargetInfo{Arn: arn, Size: 0, Duration: 0, OpType: replication.DeleteReplicationType}, replication.Pending, replication.StatusType(""))
+		globalReplicationStats.Load().Update(dv.Bucket, replicatedTargetInfo{Arn: arn, Size: 0, Duration: 0, OpType: replication.DeleteReplicationType}, replication.Pending, replication.StatusType(""))
 	}
 }
 
@@ -3042,9 +3046,9 @@ func (s *replicationResyncer) start(ctx context.Context, objAPI ObjectLayer, opt
 	if len(tgtArns) == 0 {
 		return fmt.Errorf("arn %s specified for resync not found in replication config", opts.arn)
 	}
-	globalReplicationPool.resyncer.RLock()
+	globalReplicationPool.Get().resyncer.RLock()
-	data, ok := globalReplicationPool.resyncer.statusMap[opts.bucket]
+	data, ok := globalReplicationPool.Get().resyncer.statusMap[opts.bucket]
-	globalReplicationPool.resyncer.RUnlock()
+	globalReplicationPool.Get().resyncer.RUnlock()
 	if !ok {
 		data, err = loadBucketResyncMetadata(ctx, opts.bucket, objAPI)
 		if err != nil {
@@ -3070,9 +3074,9 @@ func (s *replicationResyncer) start(ctx context.Context, objAPI ObjectLayer, opt
 		return err
 	}
 
-	globalReplicationPool.resyncer.Lock()
+	globalReplicationPool.Get().resyncer.Lock()
-	defer globalReplicationPool.resyncer.Unlock()
+	defer globalReplicationPool.Get().resyncer.Unlock()
-	brs, ok := globalReplicationPool.resyncer.statusMap[opts.bucket]
+	brs, ok := globalReplicationPool.Get().resyncer.statusMap[opts.bucket]
 	if !ok {
 		brs = BucketReplicationResyncStatus{
 			Version:    resyncMetaVersion,
@@ -3080,8 +3084,8 @@ func (s *replicationResyncer) start(ctx context.Context, objAPI ObjectLayer, opt
 		}
 	}
 	brs.TargetsMap[opts.arn] = status
-	globalReplicationPool.resyncer.statusMap[opts.bucket] = brs
+	globalReplicationPool.Get().resyncer.statusMap[opts.bucket] = brs
-	go globalReplicationPool.resyncer.resyncBucket(GlobalContext, objAPI, false, opts)
+	go globalReplicationPool.Get().resyncer.resyncBucket(GlobalContext, objAPI, false, opts)
 	return nil
 }
 
@@ -3413,7 +3417,7 @@ func queueReplicationHeal(ctx context.Context, bucket string, oi ObjectInfo, rcf
 		if roi.ReplicationStatus == replication.Pending ||
 			roi.ReplicationStatus == replication.Failed ||
 			roi.VersionPurgeStatus == Failed || roi.VersionPurgeStatus == Pending {
-			globalReplicationPool.queueReplicaDeleteTask(dv)
+			globalReplicationPool.Get().queueReplicaDeleteTask(dv)
 			return
 		}
 		// if replication status is Complete on DeleteMarker and existing object resync required
@@ -3429,12 +3433,12 @@ func queueReplicationHeal(ctx context.Context, bucket string, oi ObjectInfo, rcf
 	switch roi.ReplicationStatus {
 	case replication.Pending, replication.Failed:
 		roi.EventType = ReplicateHeal
-		globalReplicationPool.queueReplicaTask(roi)
+		globalReplicationPool.Get().queueReplicaTask(roi)
 		return
 	}
 	if roi.ExistingObjResync.mustResync() {
 		roi.EventType = ReplicateExisting
-		globalReplicationPool.queueReplicaTask(roi)
+		globalReplicationPool.Get().queueReplicaTask(roi)
 	}
 	return
 }
@@ -3499,8 +3503,8 @@ func (p *ReplicationPool) queueMRFSave(entry MRFReplicateEntry) {
 		return
 	}
 	if entry.RetryCount > mrfRetryLimit { // let scanner catch up if retry count exceeded
-		atomic.AddUint64(&globalReplicationStats.mrfStats.TotalDroppedCount, 1)
+		atomic.AddUint64(&p.stats.mrfStats.TotalDroppedCount, 1)
-		atomic.AddUint64(&globalReplicationStats.mrfStats.TotalDroppedBytes, uint64(entry.sz))
+		atomic.AddUint64(&p.stats.mrfStats.TotalDroppedBytes, uint64(entry.sz))
 		return
 	}
 
@@ -3513,8 +3517,8 @@ func (p *ReplicationPool) queueMRFSave(entry MRFReplicateEntry) {
 		select {
 		case p.mrfSaveCh <- entry:
 		default:
-			atomic.AddUint64(&globalReplicationStats.mrfStats.TotalDroppedCount, 1)
+			atomic.AddUint64(&p.stats.mrfStats.TotalDroppedCount, 1)
-			atomic.AddUint64(&globalReplicationStats.mrfStats.TotalDroppedBytes, uint64(entry.sz))
+			atomic.AddUint64(&p.stats.mrfStats.TotalDroppedBytes, uint64(entry.sz))
 		}
 	}
 }
@@ -3563,7 +3567,7 @@ func (p *ReplicationPool) saveMRFEntries(ctx context.Context, entries map[string
 	if !p.initialized() {
 		return
 	}
-	atomic.StoreUint64(&globalReplicationStats.mrfStats.LastFailedCount, uint64(len(entries)))
+	atomic.StoreUint64(&p.stats.mrfStats.LastFailedCount, uint64(len(entries)))
 	if len(entries) == 0 {
 		return
 	}

cmd/bucket-stats.go

@@ -310,7 +310,7 @@ type ReplQNodeStats struct {
 func (r *ReplicationStats) getNodeQueueStats(bucket string) (qs ReplQNodeStats) {
 	qs.NodeName = globalLocalNodeName
 	qs.Uptime = UTCNow().Unix() - globalBootTime.Unix()
-	qs.ActiveWorkers = globalReplicationStats.ActiveWorkers()
+	qs.ActiveWorkers = globalReplicationStats.Load().ActiveWorkers()
 	qs.XferStats = make(map[RMetricName]XferStats)
 	qs.QStats = r.qCache.getBucketStats(bucket)
 	qs.TgtXferStats = make(map[string]map[RMetricName]XferStats)
@@ -402,7 +402,7 @@ func (r *ReplicationStats) getNodeQueueStats(bucket string) (qs ReplQNodeStats)
 func (r *ReplicationStats) getNodeQueueStatsSummary() (qs ReplQNodeStats) {
 	qs.NodeName = globalLocalNodeName
 	qs.Uptime = UTCNow().Unix() - globalBootTime.Unix()
-	qs.ActiveWorkers = globalReplicationStats.ActiveWorkers()
+	qs.ActiveWorkers = globalReplicationStats.Load().ActiveWorkers()
 	qs.XferStats = make(map[RMetricName]XferStats)
 	qs.QStats = r.qCache.getSiteStats()
 	qs.MRFStats = ReplicationMRFStats{

cmd/handler-api.go

@@ -170,9 +170,9 @@ func (t *apiConfig) init(cfg api.Config, setDriveCounts []int, legacy bool) {
 		listQuorum = "strict"
 	}
 	t.listQuorum = listQuorum
-	if globalReplicationPool != nil &&
+	if r := globalReplicationPool.GetNonBlocking(); r != nil &&
 		(cfg.ReplicationPriority != t.replicationPriority || cfg.ReplicationMaxWorkers != t.replicationMaxWorkers || cfg.ReplicationMaxLWorkers != t.replicationMaxLWorkers) {
-		globalReplicationPool.ResizeWorkerPriority(cfg.ReplicationPriority, cfg.ReplicationMaxWorkers, cfg.ReplicationMaxLWorkers)
+		r.ResizeWorkerPriority(cfg.ReplicationPriority, cfg.ReplicationMaxWorkers, cfg.ReplicationMaxLWorkers)
 	}
 	t.replicationPriority = cfg.ReplicationPriority
 	t.replicationMaxWorkers = cfg.ReplicationMaxWorkers

cmd/metrics-v2.go

@@ -2313,8 +2313,8 @@ func getReplicationNodeMetrics(opts MetricsGroupOpts) *MetricsGroupV2 {
 		var ml []MetricV2
 		// common operational metrics for bucket replication and site replication - published
 		// at cluster level
-		if globalReplicationStats != nil {
+		if rStats := globalReplicationStats.Load(); rStats != nil {
-			qs := globalReplicationStats.getNodeQueueStatsSummary()
+			qs := rStats.getNodeQueueStatsSummary()
 			activeWorkersCount := MetricV2{
 				Description: getClusterReplActiveWorkersCountMD(),
 			}
@@ -3245,7 +3245,7 @@ func getBucketUsageMetrics(opts MetricsGroupOpts) *MetricsGroupV2 {
 
 		var bucketReplStats map[string]BucketStats
 		if !globalSiteReplicationSys.isEnabled() {
-			bucketReplStats = globalReplicationStats.getAllLatest(dataUsageInfo.BucketsUsage)
+			bucketReplStats = globalReplicationStats.Load().getAllLatest(dataUsageInfo.BucketsUsage)
 		}
 		for bucket, usage := range dataUsageInfo.BucketsUsage {
 			quota, _ := globalBucketQuotaSys.Get(ctx, bucket)

cmd/metrics-v3-bucket-replication.go

@@ -119,7 +119,7 @@ func loadBucketReplicationMetrics(ctx context.Context, m MetricValues, c *metric
 		return nil
 	}
 
-	bucketReplStats := globalReplicationStats.getAllLatest(dataUsageInfo.BucketsUsage)
+	bucketReplStats := globalReplicationStats.Load().getAllLatest(dataUsageInfo.BucketsUsage)
 	for _, bucket := range buckets {
 		labels := []string{bucketL, bucket}
 		if s, ok := bucketReplStats[bucket]; ok {

cmd/metrics-v3-replication.go

@@ -69,11 +69,12 @@ var (
 // loadClusterReplicationMetrics - `MetricsLoaderFn` for cluster replication metrics
 // such as transfer rate and objects queued.
 func loadClusterReplicationMetrics(ctx context.Context, m MetricValues, c *metricsCache) error {
-	if globalReplicationStats == nil {
+	st := globalReplicationStats.Load()
+	if st == nil {
 		return nil
 	}
 
-	qs := globalReplicationStats.getNodeQueueStatsSummary()
+	qs := st.getNodeQueueStatsSummary()
 
 	qt := qs.QStats
 	m.Set(replicationAverageQueuedBytes, float64(qt.Avg.Bytes))

cmd/metrics.go

@@ -300,7 +300,7 @@ func bucketUsageMetricsPrometheus(ch chan<- prometheus.Metric) {
 	}
 
 	for bucket, usageInfo := range dataUsageInfo.BucketsUsage {
-		stat := globalReplicationStats.getLatestReplicationStats(bucket)
+		stat := globalReplicationStats.Load().getLatestReplicationStats(bucket)
 		// Total space used by bucket
 		ch <- prometheus.MustNewConstMetric(
 			prometheus.NewDesc(

cmd/notification.go

@@ -537,7 +537,7 @@ func (sys *NotificationSys) LoadBucketMetadata(ctx context.Context, bucketName s
 
 // DeleteBucketMetadata - calls DeleteBucketMetadata call on all peers
 func (sys *NotificationSys) DeleteBucketMetadata(ctx context.Context, bucketName string) {
-	globalReplicationStats.Delete(bucketName)
+	globalReplicationStats.Load().Delete(bucketName)
 	globalBucketMetadataSys.Remove(bucketName)
 	globalBucketTargetSys.Delete(bucketName)
 	globalEventNotifier.RemoveNotification(bucketName)
@@ -591,7 +591,7 @@ func (sys *NotificationSys) GetClusterAllBucketStats(ctx context.Context) []Buck
 		}
 	}
 
-	replicationStatsList := globalReplicationStats.GetAll()
+	replicationStatsList := globalReplicationStats.Load().GetAll()
 	bucketStatsMap := BucketStatsMap{
 		Stats:     make(map[string]BucketStats, len(replicationStatsList)),
 		Timestamp: UTCNow(),
@@ -599,7 +599,7 @@ func (sys *NotificationSys) GetClusterAllBucketStats(ctx context.Context) []Buck
 	for k, replicationStats := range replicationStatsList {
 		bucketStatsMap.Stats[k] = BucketStats{
 			ReplicationStats: replicationStats,
-			ProxyStats:       globalReplicationStats.getProxyStats(k),
+			ProxyStats:       globalReplicationStats.Load().getProxyStats(k),
 		}
 	}
 
@@ -632,11 +632,13 @@ func (sys *NotificationSys) GetClusterBucketStats(ctx context.Context, bucketNam
 			peersLogOnceIf(logger.SetReqInfo(ctx, reqInfo), nErr.Err, nErr.Host.String())
 		}
 	}
+	if st := globalReplicationStats.Load(); st != nil {
 		bucketStats = append(bucketStats, BucketStats{
-		ReplicationStats: globalReplicationStats.Get(bucketName),
+			ReplicationStats: st.Get(bucketName),
-		QueueStats:       ReplicationQueueStats{Nodes: []ReplQNodeStats{globalReplicationStats.getNodeQueueStats(bucketName)}},
+			QueueStats:       ReplicationQueueStats{Nodes: []ReplQNodeStats{st.getNodeQueueStats(bucketName)}},
-		ProxyStats:       globalReplicationStats.getProxyStats(bucketName),
+			ProxyStats:       st.getProxyStats(bucketName),
 		})
+	}
 	return bucketStats
 }
 
@@ -665,7 +667,7 @@ func (sys *NotificationSys) GetClusterSiteMetrics(ctx context.Context) []SRMetri
 			peersLogOnceIf(logger.SetReqInfo(ctx, reqInfo), nErr.Err, nErr.Host.String())
 		}
 	}
-	siteStats = append(siteStats, globalReplicationStats.getSRMetricsForNode())
+	siteStats = append(siteStats, globalReplicationStats.Load().getSRMetricsForNode())
 	return siteStats
 }
 
@@ -1605,7 +1607,7 @@ func (sys *NotificationSys) GetReplicationMRF(ctx context.Context, bucket, node
 		if node != "all" && node != globalLocalNodeName {
 			return nil
 		}
-		mCh, err := globalReplicationPool.getMRF(ctx, bucket)
+		mCh, err := globalReplicationPool.Get().getMRF(ctx, bucket)
 		if err != nil {
 			return err
 		}

cmd/object-handlers.go

@@ -505,11 +505,11 @@ func (api objectAPIHandlers) getObjectHandler(ctx context.Context, objectAPI Obj
 		if (isErrObjectNotFound(err) || isErrVersionNotFound(err) || isErrReadQuorum(err)) && !(gr != nil && gr.ObjInfo.DeleteMarker) {
 			proxytgts := getProxyTargets(ctx, bucket, object, opts)
 			if !proxytgts.Empty() {
-				globalReplicationStats.incProxy(bucket, getObjectAPI, false)
+				globalReplicationStats.Load().incProxy(bucket, getObjectAPI, false)
 				// proxy to replication target if active-active replication is in place.
 				reader, proxy, perr = proxyGetToReplicationTarget(ctx, bucket, object, rs, r.Header, opts, proxytgts)
 				if perr != nil {
-					globalReplicationStats.incProxy(bucket, getObjectAPI, true)
+					globalReplicationStats.Load().incProxy(bucket, getObjectAPI, true)
 					proxyGetErr := ErrorRespToObjectError(perr, bucket, object)
 					if !isErrBucketNotFound(proxyGetErr) && !isErrObjectNotFound(proxyGetErr) && !isErrVersionNotFound(proxyGetErr) &&
 						!isErrPreconditionFailed(proxyGetErr) && !isErrInvalidRange(proxyGetErr) {
@@ -1025,14 +1025,14 @@ func (api objectAPIHandlers) headObjectHandler(ctx context.Context, objectAPI Ob
 		// proxy HEAD to replication target if active-active replication configured on bucket
 		proxytgts := getProxyTargets(ctx, bucket, object, opts)
 		if !proxytgts.Empty() {
-			globalReplicationStats.incProxy(bucket, headObjectAPI, false)
+			globalReplicationStats.Load().incProxy(bucket, headObjectAPI, false)
 			var oi ObjectInfo
 			oi, proxy = proxyHeadToReplicationTarget(ctx, bucket, object, rs, opts, proxytgts)
 			if proxy.Proxy {
 				objInfo = oi
 			}
 			if proxy.Err != nil {
-				globalReplicationStats.incProxy(bucket, headObjectAPI, true)
+				globalReplicationStats.Load().incProxy(bucket, headObjectAPI, true)
 				writeErrorResponseHeadersOnly(w, toAPIError(ctx, proxy.Err))
 				return
 			}
@@ -2090,7 +2090,7 @@ func (api objectAPIHandlers) PutObjectHandler(w http.ResponseWriter, r *http.Req
 		}
 		metadata[ReservedMetadataPrefixLower+ReplicaStatus] = replication.Replica.String()
 		metadata[ReservedMetadataPrefixLower+ReplicaTimestamp] = UTCNow().Format(time.RFC3339Nano)
-		defer globalReplicationStats.UpdateReplicaStat(bucket, size)
+		defer globalReplicationStats.Load().UpdateReplicaStat(bucket, size)
 	}
 
 	// Check if bucket encryption is enabled
@@ -3301,11 +3301,11 @@ func (api objectAPIHandlers) GetObjectTaggingHandler(w http.ResponseWriter, r *h
 		if isErrObjectNotFound(err) || isErrVersionNotFound(err) {
 			proxytgts := getProxyTargets(ctx, bucket, object, opts)
 			if !proxytgts.Empty() {
-				globalReplicationStats.incProxy(bucket, getObjectTaggingAPI, false)
+				globalReplicationStats.Load().incProxy(bucket, getObjectTaggingAPI, false)
 				// proxy to replication target if site replication is in place.
 				tags, gerr := proxyGetTaggingToRepTarget(ctx, bucket, object, opts, proxytgts)
 				if gerr.Err != nil || tags == nil {
-					globalReplicationStats.incProxy(bucket, getObjectTaggingAPI, true)
+					globalReplicationStats.Load().incProxy(bucket, getObjectTaggingAPI, true)
 					writeErrorResponse(ctx, w, toAPIError(ctx, gerr.Err), r.URL)
 					return
 				} // overlay tags from peer site.
@@ -3404,11 +3404,11 @@ func (api objectAPIHandlers) PutObjectTaggingHandler(w http.ResponseWriter, r *h
 		if isErrObjectNotFound(err) || isErrVersionNotFound(err) {
 			proxytgts := getProxyTargets(ctx, bucket, object, opts)
 			if !proxytgts.Empty() {
-				globalReplicationStats.incProxy(bucket, putObjectTaggingAPI, false)
+				globalReplicationStats.Load().incProxy(bucket, putObjectTaggingAPI, false)
 				// proxy to replication target if site replication is in place.
 				perr := proxyTaggingToRepTarget(ctx, bucket, object, tags, opts, proxytgts)
 				if perr.Err != nil {
-					globalReplicationStats.incProxy(bucket, putObjectTaggingAPI, true)
+					globalReplicationStats.Load().incProxy(bucket, putObjectTaggingAPI, true)
 					writeErrorResponse(ctx, w, toAPIError(ctx, perr.Err), r.URL)
 					return
 				}
@@ -3501,11 +3501,11 @@ func (api objectAPIHandlers) DeleteObjectTaggingHandler(w http.ResponseWriter, r
 		if isErrObjectNotFound(err) || isErrVersionNotFound(err) {
 			proxytgts := getProxyTargets(ctx, bucket, object, opts)
 			if !proxytgts.Empty() {
-				globalReplicationStats.incProxy(bucket, removeObjectTaggingAPI, false)
+				globalReplicationStats.Load().incProxy(bucket, removeObjectTaggingAPI, false)
 				// proxy to replication target if active-active replication is in place.
 				perr := proxyTaggingToRepTarget(ctx, bucket, object, nil, opts, proxytgts)
 				if perr.Err != nil {
-					globalReplicationStats.incProxy(bucket, removeObjectTaggingAPI, true)
+					globalReplicationStats.Load().incProxy(bucket, removeObjectTaggingAPI, true)
 					writeErrorResponse(ctx, w, toAPIError(ctx, perr.Err), r.URL)
 					return
 				}

cmd/object-multipart-handlers.go

@@ -1029,7 +1029,7 @@ func (api objectAPIHandlers) CompleteMultipartUploadHandler(w http.ResponseWrite
 	}
 	if _, ok := r.Header[xhttp.MinIOSourceReplicationRequest]; ok {
 		actualSize, _ := objInfo.GetActualSize()
-		defer globalReplicationStats.UpdateReplicaStat(bucket, actualSize)
+		defer globalReplicationStats.Load().UpdateReplicaStat(bucket, actualSize)
 	}
 
 	// Get object location.

cmd/peer-rest-server.go

@@ -469,7 +469,7 @@ func (s *peerRESTServer) DeleteBucketMetadataHandler(mss *grid.MSS) (np grid.NoP
 		return np, grid.NewRemoteErr(errors.New("Bucket name is missing"))
 	}
 
-	globalReplicationStats.Delete(bucketName)
+	globalReplicationStats.Load().Delete(bucketName)
 	globalBucketMetadataSys.Remove(bucketName)
 	globalBucketTargetSys.Delete(bucketName)
 	globalEventNotifier.RemoveNotification(bucketName)
@@ -483,12 +483,12 @@ func (s *peerRESTServer) DeleteBucketMetadataHandler(mss *grid.MSS) (np grid.NoP
 
 // GetAllBucketStatsHandler - fetches bucket replication stats for all buckets from this peer.
 func (s *peerRESTServer) GetAllBucketStatsHandler(mss *grid.MSS) (*BucketStatsMap, *grid.RemoteErr) {
-	replicationStats := globalReplicationStats.GetAll()
+	replicationStats := globalReplicationStats.Load().GetAll()
 	bucketStatsMap := make(map[string]BucketStats, len(replicationStats))
 	for k, v := range replicationStats {
 		bucketStatsMap[k] = BucketStats{
 			ReplicationStats: v,
-			ProxyStats:       globalReplicationStats.getProxyStats(k),
+			ProxyStats:       globalReplicationStats.Load().getProxyStats(k),
 		}
 	}
 	return &BucketStatsMap{Stats: bucketStatsMap, Timestamp: time.Now()}, nil
@@ -501,11 +501,14 @@ func (s *peerRESTServer) GetBucketStatsHandler(vars *grid.MSS) (*BucketStats, *g
 	if bucketName == "" {
 		return nil, grid.NewRemoteErrString("Bucket name is missing")
 	}
-
+	st := globalReplicationStats.Load()
+	if st == nil {
+		return &BucketStats{}, nil
+	}
 	bs := BucketStats{
-		ReplicationStats: globalReplicationStats.Get(bucketName),
+		ReplicationStats: st.Get(bucketName),
-		QueueStats:       ReplicationQueueStats{Nodes: []ReplQNodeStats{globalReplicationStats.getNodeQueueStats(bucketName)}},
+		QueueStats:       ReplicationQueueStats{Nodes: []ReplQNodeStats{st.getNodeQueueStats(bucketName)}},
-		ProxyStats:       globalReplicationStats.getProxyStats(bucketName),
+		ProxyStats:       st.getProxyStats(bucketName),
 	}
 	return &bs, nil
 }
@@ -516,9 +519,11 @@ func (s *peerRESTServer) GetSRMetricsHandler(mss *grid.MSS) (*SRMetricsSummary,
 	if objAPI == nil {
 		return nil, grid.NewRemoteErr(errServerNotInitialized)
 	}
-
+	if st := globalReplicationStats.Load(); st != nil {
-	sm := globalReplicationStats.getSRMetricsForNode()
+		sm := st.getSRMetricsForNode()
 		return &sm, nil
+	}
+	return &SRMetricsSummary{}, nil
 }
 
 // LoadBucketMetadataHandler - reloads in memory bucket metadata
@@ -1173,7 +1178,7 @@ func (s *peerRESTServer) GetReplicationMRFHandler(w http.ResponseWriter, r *http
 	vars := mux.Vars(r)
 	bucketName := vars[peerRESTBucket]
 	ctx := newContext(r, w, "GetReplicationMRF")
-	re, err := globalReplicationPool.getMRF(ctx, bucketName)
+	re, err := globalReplicationPool.Get().getMRF(ctx, bucketName)
 	if err != nil {
 		s.writeErrorResponse(w, err)
 		return

cmd/server-main.go

@@ -1082,7 +1082,7 @@ func serverMain(ctx *cli.Context) {
 
 		// initialize replication resync state.
 		bootstrapTrace("initResync", func() {
-			globalReplicationPool.initResync(GlobalContext, buckets, newObject)
+			globalReplicationPool.Get().initResync(GlobalContext, buckets, newObject)
 		})
 
 		// Initialize site replication manager after bucket metadata

cmd/site-replication.go

@@ -5858,7 +5858,7 @@ func (c *SiteReplicationSys) startResync(ctx context.Context, objAPI ObjectLayer
 			})
 			continue
 		}
-		if err := globalReplicationPool.resyncer.start(ctx, objAPI, resyncOpts{
+		if err := globalReplicationPool.Get().resyncer.start(ctx, objAPI, resyncOpts{
 			bucket:   bucket,
 			arn:      tgtArn,
 			resyncID: rs.ResyncID,
@@ -5953,8 +5953,8 @@ func (c *SiteReplicationSys) cancelResync(ctx context.Context, objAPI ObjectLaye
 				continue
 			}
 			// update resync state for the bucket
-			globalReplicationPool.resyncer.Lock()
+			globalReplicationPool.Get().resyncer.Lock()
-			m, ok := globalReplicationPool.resyncer.statusMap[bucket]
+			m, ok := globalReplicationPool.Get().resyncer.statusMap[bucket]
 			if !ok {
 				m = newBucketResyncStatus(bucket)
 			}
@@ -5964,8 +5964,8 @@ func (c *SiteReplicationSys) cancelResync(ctx context.Context, objAPI ObjectLaye
 				m.TargetsMap[t.Arn] = st
 				m.LastUpdate = UTCNow()
 			}
-			globalReplicationPool.resyncer.statusMap[bucket] = m
+			globalReplicationPool.Get().resyncer.statusMap[bucket] = m
-			globalReplicationPool.resyncer.Unlock()
+			globalReplicationPool.Get().resyncer.Unlock()
 		}
 	}
 
@@ -5975,7 +5975,7 @@ func (c *SiteReplicationSys) cancelResync(ctx context.Context, objAPI ObjectLaye
 		return res, err
 	}
 	select {
-	case globalReplicationPool.resyncer.resyncCancelCh <- struct{}{}:
+	case globalReplicationPool.Get().resyncer.resyncCancelCh <- struct{}{}:
 	case <-ctx.Done():
 	}
 

cmd/test-utils_test.go

@@ -351,7 +351,9 @@ func initTestServerWithBackend(ctx context.Context, t TestErrHandler, testServer
 	// Test Server needs to start before formatting of disks.
 	// Get credential.
 	credentials := globalActiveCred
-
+	if !globalReplicationPool.IsSet() {
+		globalReplicationPool.Set(nil)
+	}
 	testServer.Obj = objLayer
 	testServer.rawDiskPaths = disks
 	testServer.Disks = mustGetPoolEndpoints(0, disks...)

internal/once/singleton.go

@@ -0,0 +1,46 @@
+package once
+
+// Singleton contains a pointer to T that must be set once.
+// Until the value is set all Get() calls will block.
+type Singleton[T any] struct {
+	v   *T
+	set chan struct{}
+}
+
+// NewSingleton creates a new unset singleton.
+func NewSingleton[T any]() *Singleton[T] {
+	return &Singleton[T]{set: make(chan struct{}), v: nil}
+}
+
+// Get will return the singleton value.
+func (s *Singleton[T]) Get() *T {
+	<-s.set
+	return s.v
+}
+
+// GetNonBlocking will return the singleton value or nil if not set yet.
+func (s *Singleton[T]) GetNonBlocking() *T {
+	select {
+	case <-s.set:
+		return s.v
+	default:
+		return nil
+	}
+}
+
+// IsSet will return whether the singleton has been set.
+func (s *Singleton[T]) IsSet() bool {
+	select {
+	case <-s.set:
+		return true
+	default:
+		return false
+	}
+}
+
+// Set the value and unblock all Get requests.
+// This may only be called once, a second call will panic.
+func (s *Singleton[T]) Set(v *T) {
+	s.v = v
+	close(s.set)
+}