Allow configuring the maximum number of concurrent tasks for EC parallelization. (#6376)

Follow-up to b0210df0.

weed/shell/command_ec_balance.go

@@ -35,7 +35,7 @@ func (c *commandEcBalance) Do(args []string, commandEnv *CommandEnv, writer io.W
 	collection := balanceCommand.String("collection", "EACH_COLLECTION", "collection name, or \"EACH_COLLECTION\" for each collection")
 	dc := balanceCommand.String("dataCenter", "", "only apply the balancing for this dataCenter")
 	shardReplicaPlacement := balanceCommand.String("shardReplicaPlacement", "", "replica placement for EC shards, or master default if empty")
-	parallelize := balanceCommand.Bool("parallelize", true, "parallelize operations whenever possible")
+	maxParallelization := balanceCommand.Int("maxParallelization", 10, "run up to X tasks in parallel, whenever possible")
 	applyBalancing := balanceCommand.Bool("force", false, "apply the balancing plan")
 	if err = balanceCommand.Parse(args); err != nil {
 		return nil
@@ -62,5 +62,5 @@ func (c *commandEcBalance) Do(args []string, commandEnv *CommandEnv, writer io.W
 		return err
 	}
 
-	return EcBalance(commandEnv, collections, *dc, rp, *parallelize, *applyBalancing)
+	return EcBalance(commandEnv, collections, *dc, rp, *maxParallelization, *applyBalancing)
 }

weed/shell/command_ec_common.go

@@ -114,47 +114,50 @@ var (
 )
 
 type ErrorWaitGroup struct {
-	parallelize bool
+	maxConcurrency int
 	wg             *sync.WaitGroup
+	wgSem          chan bool
 	errors         []error
 	errorsMu       sync.Mutex
 }
 type ErrorWaitGroupTask func() error
 
-func (ewg *ErrorWaitGroup) Init() {
-	if ewg.wg != nil {
-		return
+func NewErrorWaitGroup(maxConcurrency int) *ErrorWaitGroup {
+	if maxConcurrency <= 0 {
+		// No concurrency = one task at the time
+		maxConcurrency = 1
+	}
+	return &ErrorWaitGroup{
+		maxConcurrency: maxConcurrency,
+		wg:             &sync.WaitGroup{},
+		wgSem:          make(chan bool, maxConcurrency),
 	}
-	ewg.wg = &sync.WaitGroup{}
-	ewg.errors = nil
 }
 
 func (ewg *ErrorWaitGroup) Add(f ErrorWaitGroupTask) {
-	if ewg.wg == nil || !ewg.parallelize {
+	if ewg.maxConcurrency <= 1 {
+		// Keep run order deterministic when parallelization is off
 		ewg.errors = append(ewg.errors, f())
 		return
 	}
 
 	ewg.wg.Add(1)
 	go func() {
+		ewg.wgSem <- true
+
 		err := f()
 		ewg.errorsMu.Lock()
 		ewg.errors = append(ewg.errors, err)
 		ewg.errorsMu.Unlock()
+
+		<-ewg.wgSem
 		ewg.wg.Done()
 	}()
 }
 
 func (ewg *ErrorWaitGroup) Wait() error {
-	if ewg.wg != nil {
 	ewg.wg.Wait()
-	}
-
-	err := errors.Join(ewg.errors...)
-	ewg.wg = nil
-	ewg.errors = nil
-
-	return err
+	return errors.Join(ewg.errors...)
 }
 
 func _getDefaultReplicaPlacement(commandEnv *CommandEnv) (*super_block.ReplicaPlacement, error) {
@@ -601,8 +604,11 @@ type ecBalancer struct {
 	ecNodes            []*EcNode
 	replicaPlacement   *super_block.ReplicaPlacement
 	applyBalancing     bool
+	maxParallelization int
+}
 
-	ewg ErrorWaitGroup
+func (ecb *ecBalancer) errorWaitGroup() *ErrorWaitGroup {
+	return NewErrorWaitGroup(ecb.maxParallelization)
 }
 
 func (ecb *ecBalancer) racks() map[RackId]*EcRack {
@@ -641,13 +647,13 @@ func (ecb *ecBalancer) balanceEcVolumes(collection string) error {
 func (ecb *ecBalancer) deleteDuplicatedEcShards(collection string) error {
 	vidLocations := ecb.collectVolumeIdToEcNodes(collection)
 
-	ecb.ewg.Init()
+	ewg := ecb.errorWaitGroup()
 	for vid, locations := range vidLocations {
-		ecb.ewg.Add(func() error {
+		ewg.Add(func() error {
 			return ecb.doDeduplicateEcShards(collection, vid, locations)
 		})
 	}
-	return ecb.ewg.Wait()
+	return ewg.Wait()
 }
 
 func (ecb *ecBalancer) doDeduplicateEcShards(collection string, vid needle.VolumeId, locations []*EcNode) error {
@@ -688,13 +694,13 @@ func (ecb *ecBalancer) balanceEcShardsAcrossRacks(collection string) error {
 	vidLocations := ecb.collectVolumeIdToEcNodes(collection)
 
 	// spread the ec shards evenly
-	ecb.ewg.Init()
+	ewg := ecb.errorWaitGroup()
 	for vid, locations := range vidLocations {
-		ecb.ewg.Add(func() error {
+		ewg.Add(func() error {
 			return ecb.doBalanceEcShardsAcrossRacks(collection, vid, locations)
 		})
 	}
-	return ecb.ewg.Wait()
+	return ewg.Wait()
 }
 
 func countShardsByRack(vid needle.VolumeId, locations []*EcNode) map[string]int {
@@ -796,7 +802,7 @@ func (ecb *ecBalancer) balanceEcShardsWithinRacks(collection string) error {
 	racks := ecb.racks()
 
 	// spread the ec shards evenly
-	ecb.ewg.Init()
+	ewg := ecb.errorWaitGroup()
 	for vid, locations := range vidLocations {
 
 		// see the volume's shards are in how many racks, and how many in each rack
@@ -815,12 +821,12 @@ func (ecb *ecBalancer) balanceEcShardsWithinRacks(collection string) error {
 			}
 			sourceEcNodes := rackEcNodesWithVid[rackId]
 			averageShardsPerEcNode := ceilDivide(rackToShardCount[rackId], len(possibleDestinationEcNodes))
-			ecb.ewg.Add(func() error {
+			ewg.Add(func() error {
 				return ecb.doBalanceEcShardsWithinOneRack(averageShardsPerEcNode, collection, vid, sourceEcNodes, possibleDestinationEcNodes)
 			})
 		}
 	}
-	return ecb.ewg.Wait()
+	return ewg.Wait()
 }
 
 func (ecb *ecBalancer) doBalanceEcShardsWithinOneRack(averageShardsPerEcNode int, collection string, vid needle.VolumeId, existingLocations, possibleDestinationEcNodes []*EcNode) error {
@@ -851,13 +857,13 @@ func (ecb *ecBalancer) doBalanceEcShardsWithinOneRack(averageShardsPerEcNode int
 
 func (ecb *ecBalancer) balanceEcRacks() error {
 	// balance one rack for all ec shards
-	ecb.ewg.Init()
+	ewg := ecb.errorWaitGroup()
 	for _, ecRack := range ecb.racks() {
-		ecb.ewg.Add(func() error {
+		ewg.Add(func() error {
 			return ecb.doBalanceEcRack(ecRack)
 		})
 	}
-	return ecb.ewg.Wait()
+	return ewg.Wait()
 }
 
 func (ecb *ecBalancer) doBalanceEcRack(ecRack *EcRack) error {
@@ -1052,7 +1058,7 @@ func (ecb *ecBalancer) collectVolumeIdToEcNodes(collection string) map[needle.Vo
 	return vidLocations
 }
 
-func EcBalance(commandEnv *CommandEnv, collections []string, dc string, ecReplicaPlacement *super_block.ReplicaPlacement, parallelize bool, applyBalancing bool) (err error) {
+func EcBalance(commandEnv *CommandEnv, collections []string, dc string, ecReplicaPlacement *super_block.ReplicaPlacement, maxParallelization int, applyBalancing bool) (err error) {
 	if len(collections) == 0 {
 		return fmt.Errorf("no collections to balance")
 	}
@@ -1071,10 +1077,7 @@ func EcBalance(commandEnv *CommandEnv, collections []string, dc string, ecReplic
 		ecNodes:            allEcNodes,
 		replicaPlacement:   ecReplicaPlacement,
 		applyBalancing:     applyBalancing,
-
-		ewg: ErrorWaitGroup{
-			parallelize: parallelize,
-		},
+		maxParallelization: maxParallelization,
 	}
 
 	for _, c := range collections {

weed/shell/command_ec_encode.go

@@ -65,7 +65,7 @@ func (c *commandEcEncode) Do(args []string, commandEnv *CommandEnv, writer io.Wr
 	collection := encodeCommand.String("collection", "", "the collection name")
 	fullPercentage := encodeCommand.Float64("fullPercent", 95, "the volume reaches the percentage of max volume size")
 	quietPeriod := encodeCommand.Duration("quietFor", time.Hour, "select volumes without no writes for this period")
-	parallelize := encodeCommand.Bool("parallelize", true, "parallelize operations whenever possible")
+	maxParallelization := encodeCommand.Int("maxParallelization", 10, "run up to X tasks in parallel, whenever possible")
 	forceChanges := encodeCommand.Bool("force", false, "force the encoding even if the cluster has less than recommended 4 nodes")
 	shardReplicaPlacement := encodeCommand.String("shardReplicaPlacement", "", "replica placement for EC shards, or master default if empty")
 	applyBalancing := encodeCommand.Bool("rebalance", false, "re-balance EC shards after creation")
@@ -124,7 +124,7 @@ func (c *commandEcEncode) Do(args []string, commandEnv *CommandEnv, writer io.Wr
 		}
 	}
 	// ...then re-balance ec shards.
-	if err := EcBalance(commandEnv, collections, "", rp, *parallelize, *applyBalancing); err != nil {
+	if err := EcBalance(commandEnv, collections, "", rp, *maxParallelization, *applyBalancing); err != nil {
 		return fmt.Errorf("re-balance ec shards for collection(s) %v: %v", collections, err)
 	}