add sortEcNodesByFreeslotsDecending and sortEcNodesByFreeslotsAscending

addressing https://github.com/chrislusf/seaweedfs/issues/1111

weed/shell/command_ec_balance.go

@@ -207,7 +207,7 @@ func doDeduplicateEcShards(ctx context.Context, commandEnv *CommandEnv, collecti
 		if len(ecNodes) <= 1 {
 			continue
 		}
-		sortEcNodes(ecNodes)
+		sortEcNodesByFreeslotsAscending(ecNodes)
 		fmt.Printf("ec shard %d.%d has %d copies, keeping %v\n", vid, shardId, len(ecNodes), ecNodes[0].info.Id)
 		if !applyBalancing {
 			continue
@@ -442,7 +442,7 @@ func doBalanceEcRack(ctx context.Context, commandEnv *CommandEnv, ecRack *EcRack
 
 func pickOneEcNodeAndMoveOneShard(ctx context.Context, commandEnv *CommandEnv, expectedTotalEcShards int, existingLocation *EcNode, collection string, vid needle.VolumeId, shardId erasure_coding.ShardId, possibleDestinationEcNodes []*EcNode, applyBalancing bool) error {
 
-	sortEcNodes(possibleDestinationEcNodes)
+	sortEcNodesByFreeslotsDecending(possibleDestinationEcNodes)
 	averageShardsPerEcNode := ceilDivide(expectedTotalEcShards, len(possibleDestinationEcNodes))
 
 	for _, destEcNode := range possibleDestinationEcNodes {

weed/shell/command_ec_common.go

@@ -112,12 +112,18 @@ func eachDataNode(topo *master_pb.TopologyInfo, fn func(dc string, rack RackId,
 	}
 }
 
-func sortEcNodes(ecNodes []*EcNode) {
+func sortEcNodesByFreeslotsDecending(ecNodes []*EcNode) {
 	sort.Slice(ecNodes, func(i, j int) bool {
 		return ecNodes[i].freeEcSlot > ecNodes[j].freeEcSlot
 	})
 }
 
+func sortEcNodesByFreeslotsAscending(ecNodes []*EcNode) {
+	sort.Slice(ecNodes, func(i, j int) bool {
+		return ecNodes[i].freeEcSlot < ecNodes[j].freeEcSlot
+	})
+}
+
 type CandidateEcNode struct {
 	ecNode     *EcNode
 	shardCount int
@@ -202,7 +208,7 @@ func collectEcNodes(ctx context.Context, commandEnv *CommandEnv, selectedDataCen
 		totalFreeEcSlots += freeEcSlots
 	})
 
-	sortEcNodes(ecNodes)
+	sortEcNodesByFreeslotsDecending(ecNodes)
 
 	return
 }

weed/shell/command_ec_rebuild.go

@@ -111,7 +111,7 @@ func rebuildEcVolumes(commandEnv *CommandEnv, allEcNodes []*EcNode, collection s
 			return fmt.Errorf("ec volume %d is unrepairable with %d shards\n", vid, shardCount)
 		}
 
-		sortEcNodes(allEcNodes)
+		sortEcNodesByFreeslotsDecending(allEcNodes)
 
 		if allEcNodes[0].freeEcSlot < erasure_coding.TotalShardsCount {
 			return fmt.Errorf("disk space is not enough")