func NewReplicationStats(ctx context.Context, objectAPI ObjectLayer) *ReplicationStats {
	r := metrics.NewRegistry()
	rs := ReplicationStats{
		Cache:           make(map[string]*BucketReplicationStats),
		qCache:          newQueueCache(r),
		pCache:          newProxyStatsCache(),
		srStats:         newSRStats(),
		movingAvgTicker: time.NewTicker(2 * time.Second),
		wTimer:          time.NewTicker(2 * time.Second),

		Max:  qm.Max.add(o.Max),
	}
}

type queueCache struct {
	srQueueStats InQueueStats
	bucketStats  map[string]InQueueStats
	sync.RWMutex // mutex for queue stats
}

func newQueueCache(r metrics.Registry) queueCache {
	return queueCache{
		bucketStats:  make(map[string]InQueueStats),
		srQueueStats: newInQueueStats(r, "site"),
	}
}

func (q *queueCache) update() {
	q.Lock()