cluster: avoid unexpected statistic modify in range cluster (#3599)

server/core/store_option.go

@@ -187,6 +187,17 @@ func SetStoreStats(stats *pdpb.StoreStats) StoreCreateOption {
 	}
 }
 
+// SetNewStoreStats sets the raw statistics information for the store.
+func SetNewStoreStats(stats *pdpb.StoreStats) StoreCreateOption {
+	return func(store *StoreInfo) {
+		// There is no clone in default store stats, we create new one to avoid to modify others.
+		// And range cluster cannot use HMA because the last value is not cached
+		store.storeStats = &storeStats{
+			rawStats: stats,
+		}
+	}
+}
+
 // AttachAvailableFunc attaches a customize function for the store. The function f returns true if the store limit is not exceeded.
 func AttachAvailableFunc(limitType storelimit.Type, f func() bool) StoreCreateOption {
 	return func(store *StoreInfo) {

server/core/store_stats.go

@@ -49,6 +49,10 @@ func (ss *storeStats) updateRawStats(rawStats *pdpb.StoreStats) {
 	defer ss.mu.Unlock()
 	ss.rawStats = rawStats
 
+	if ss.avgAvailable == nil {
+		return
+	}
+
 	ss.avgAvailable.Add(float64(rawStats.GetAvailable()))
 	deviation := math.Abs(float64(rawStats.GetAvailable()) - ss.avgAvailable.Get())
 	ss.maxAvailableDeviation.Add(deviation)
@@ -143,13 +147,19 @@ func (ss *storeStats) GetApplyingSnapCount() uint32 {
 func (ss *storeStats) GetAvgAvailable() uint64 {
 	ss.mu.RLock()
 	defer ss.mu.RUnlock()
+	if ss.avgAvailable == nil {
+		return ss.rawStats.Available
+	}
 	return climp0(ss.avgAvailable.Get())
 }
 
 // GetAvailableDeviation returns approximate magnitude of available in the recent period.
 func (ss *storeStats) GetAvailableDeviation() uint64 {
 	ss.mu.RLock()
 	defer ss.mu.RUnlock()
+	if ss.avgMaxAvailableDeviation == nil {
+		return 0
+	}
 	return climp0(ss.avgMaxAvailableDeviation.Get())
 }
 

server/schedule/range_cluster.go

@@ -57,7 +57,7 @@ func (r *RangeCluster) updateStoreInfo(s *core.StoreInfo) *core.StoreInfo {
 	newStats.UsedSize = uint64(float64(regionSize)/amplification) * (1 << 20)
 	newStats.Available = s.GetCapacity() - newStats.UsedSize
 	newStore := s.Clone(
-		core.SetStoreStats(newStats),
+		core.SetNewStoreStats(newStats), // it means to use instant value directly
 		core.SetLeaderCount(leaderCount),
 		core.SetRegionCount(regionCount),
 		core.SetPendingPeerCount(pendingPeerCount),