Respect -minFreeSpace during ec.decode (#8467)

* shell: add ec.decode ignoreMinFreeSpace flag

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* shell: respect minFreeSpace in ec.decode

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* shell: rename ec.decode minFreeSpace flag

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* shell: error when ec.decode has no shards

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* shell: select ec.decode target with zero shards

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* shell: adjust free counts across ec.decode

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* unused

* Update weed/shell/command_ec_decode.go

Co-authored-by: coderabbitai[bot] <136622811+coderabbitai[bot]@users.noreply.github.com>

---------

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Co-authored-by: coderabbitai[bot] <136622811+coderabbitai[bot]@users.noreply.github.com>

weed/shell/command_ec_decode.go

@@ -35,7 +35,7 @@ func (c *commandEcDecode) Name() string {
 func (c *commandEcDecode) Help() string {
 	return `decode a erasure coded volume into a normal volume
 
-	ec.decode [-collection=""] [-volumeId=<volume_id>] [-diskType=<disk_type>]
+	ec.decode [-collection=""] [-volumeId=<volume_id>] [-diskType=<disk_type>] [-checkMinFreeSpace]
 
 	The -collection parameter supports regular expressions for pattern matching:
 	  - Use exact match: ec.decode -collection="^mybucket$"
@@ -44,6 +44,7 @@ func (c *commandEcDecode) Help() string {
 
 	Options:
 	  -diskType: source disk type where EC shards are stored (hdd, ssd, or empty for default hdd)
+	  -checkMinFreeSpace: check min free space when selecting the decode target (default true)
 
 	Examples:
 	  # Decode EC shards from HDD (default)
@@ -64,6 +65,7 @@ func (c *commandEcDecode) Do(args []string, commandEnv *CommandEnv, writer io.Wr
 	volumeId := decodeCommand.Int("volumeId", 0, "the volume id")
 	collection := decodeCommand.String("collection", "", "the collection name")
 	diskTypeStr := decodeCommand.String("diskType", "", "source disk type where EC shards are stored (hdd, ssd, or empty for default hdd)")
+	checkMinFreeSpace := decodeCommand.Bool("checkMinFreeSpace", true, "check min free space when selecting the decode target")
 	if err = decodeCommand.Parse(args); err != nil {
 		return nil
 	}
@@ -80,10 +82,14 @@ func (c *commandEcDecode) Do(args []string, commandEnv *CommandEnv, writer io.Wr
 	if err != nil {
 		return err
 	}
+	var diskUsageState *decodeDiskUsageState
+	if *checkMinFreeSpace {
+		diskUsageState = newDecodeDiskUsageState(topologyInfo, diskType)
+	}
 
 	// volumeId is provided
 	if vid != 0 {
-		return doEcDecode(commandEnv, topologyInfo, *collection, vid, diskType)
+		return doEcDecode(commandEnv, topologyInfo, *collection, vid, diskType, *checkMinFreeSpace, diskUsageState)
 	}
 
 	// apply to all volumes in the collection
@@ -93,7 +99,7 @@ func (c *commandEcDecode) Do(args []string, commandEnv *CommandEnv, writer io.Wr
 	}
 	fmt.Printf("ec decode volumes: %v\n", volumeIds)
 	for _, vid := range volumeIds {
-		if err = doEcDecode(commandEnv, topologyInfo, *collection, vid, diskType); err != nil {
+		if err = doEcDecode(commandEnv, topologyInfo, *collection, vid, diskType, *checkMinFreeSpace, diskUsageState); err != nil {
 			return err
 		}
 	}
@@ -101,7 +107,7 @@ func (c *commandEcDecode) Do(args []string, commandEnv *CommandEnv, writer io.Wr
 	return nil
 }
 
-func doEcDecode(commandEnv *CommandEnv, topoInfo *master_pb.TopologyInfo, collection string, vid needle.VolumeId, diskType types.DiskType) (err error) {
+func doEcDecode(commandEnv *CommandEnv, topoInfo *master_pb.TopologyInfo, collection string, vid needle.VolumeId, diskType types.DiskType, checkMinFreeSpace bool, diskUsageState *decodeDiskUsageState) (err error) {
 
 	if !commandEnv.isLocked() {
 		return fmt.Errorf("lock is lost")
@@ -112,8 +118,36 @@ func doEcDecode(commandEnv *CommandEnv, topoInfo *master_pb.TopologyInfo, collec
 
 	fmt.Printf("ec volume %d shard locations: %+v\n", vid, nodeToEcShardsInfo)
 
+	if len(nodeToEcShardsInfo) == 0 {
+		return fmt.Errorf("no EC shards found for volume %d (diskType %s)", vid, diskType.ReadableString())
+	}
+
+	var originalShardCounts map[pb.ServerAddress]int
+	if diskUsageState != nil {
+		originalShardCounts = make(map[pb.ServerAddress]int, len(nodeToEcShardsInfo))
+		for location, si := range nodeToEcShardsInfo {
+			originalShardCounts[location] = si.Count()
+		}
+	}
+
+	var eligibleTargets map[pb.ServerAddress]struct{}
+	if checkMinFreeSpace {
+		if diskUsageState == nil {
+			return fmt.Errorf("min free space checking requires disk usage state")
+		}
+		eligibleTargets = make(map[pb.ServerAddress]struct{})
+		for location := range nodeToEcShardsInfo {
+			if freeCount, found := diskUsageState.freeVolumeCount(location); found && freeCount > 0 {
+				eligibleTargets[location] = struct{}{}
+			}
+		}
+		if len(eligibleTargets) == 0 {
+			return fmt.Errorf("no eligible target datanodes with free volume slots for volume %d (diskType %s); use -checkMinFreeSpace=false to override", vid, diskType.ReadableString())
+		}
+	}
+
 	// collect ec shards to the server with most space
-	targetNodeLocation, err := collectEcShards(commandEnv, nodeToEcShardsInfo, collection, vid)
+	targetNodeLocation, err := collectEcShards(commandEnv, nodeToEcShardsInfo, collection, vid, eligibleTargets)
 	if err != nil {
 		return fmt.Errorf("collectEcShards for volume %d: %v", vid, err)
 	}
@@ -124,7 +158,13 @@ func doEcDecode(commandEnv *CommandEnv, topoInfo *master_pb.TopologyInfo, collec
 		// Special case: if the EC index has no live entries, decoding is a no-op.
 		// Just purge EC shards and return success without generating/mounting an empty volume.
 		if isEcDecodeEmptyVolumeErr(err) {
-			return unmountAndDeleteEcShards(commandEnv.option.GrpcDialOption, collection, nodeToEcShardsInfo, vid)
+			if err := unmountAndDeleteEcShards(commandEnv.option.GrpcDialOption, collection, nodeToEcShardsInfo, vid); err != nil {
+				return err
+			}
+			if diskUsageState != nil {
+				diskUsageState.applyDecode(targetNodeLocation, originalShardCounts, false)
+			}
+			return nil
 		}
 		return fmt.Errorf("generate normal volume %d on %s: %v", vid, targetNodeLocation, err)
 	}
@@ -134,6 +174,9 @@ func doEcDecode(commandEnv *CommandEnv, topoInfo *master_pb.TopologyInfo, collec
 	if err != nil {
 		return fmt.Errorf("delete ec shards for volume %d: %v", vid, err)
 	}
+	if diskUsageState != nil {
+		diskUsageState.applyDecode(targetNodeLocation, originalShardCounts, true)
+	}
 
 	return nil
 }
@@ -207,11 +250,16 @@ func generateNormalVolume(grpcDialOption grpc.DialOption, vid needle.VolumeId, c
 
 }
 
-func collectEcShards(commandEnv *CommandEnv, nodeToShardsInfo map[pb.ServerAddress]*erasure_coding.ShardsInfo, collection string, vid needle.VolumeId) (targetNodeLocation pb.ServerAddress, err error) {
+func collectEcShards(commandEnv *CommandEnv, nodeToShardsInfo map[pb.ServerAddress]*erasure_coding.ShardsInfo, collection string, vid needle.VolumeId, eligibleTargets map[pb.ServerAddress]struct{}) (targetNodeLocation pb.ServerAddress, err error) {
 
-	maxShardCount := 0
+	maxShardCount := -1
 	existingShardsInfo := erasure_coding.NewShardsInfo()
 	for loc, si := range nodeToShardsInfo {
+		if eligibleTargets != nil {
+			if _, ok := eligibleTargets[loc]; !ok {
+				continue
+			}
+		}
 		toBeCopiedShardCount := si.MinusParityShards().Count()
 		if toBeCopiedShardCount > maxShardCount {
 			maxShardCount = toBeCopiedShardCount
@@ -219,6 +267,9 @@ func collectEcShards(commandEnv *CommandEnv, nodeToShardsInfo map[pb.ServerAddre
 			existingShardsInfo = si
 		}
 	}
+	if targetNodeLocation == "" {
+		return "", fmt.Errorf("no eligible target datanodes available to decode volume %d", vid)
+	}
 
 	fmt.Printf("collectEcShards: ec volume %d collect shards to %s from: %+v\n", vid, targetNodeLocation, nodeToShardsInfo)
 
@@ -326,3 +377,58 @@ func collectEcNodeShardsInfo(topoInfo *master_pb.TopologyInfo, vid needle.Volume
 
 	return res
 }
+
+type decodeDiskUsageState struct {
+	byNode map[pb.ServerAddress]*decodeDiskUsageCounts
+}
+
+type decodeDiskUsageCounts struct {
+	maxVolumeCount    int64
+	volumeCount       int64
+	remoteVolumeCount int64
+	ecShardCount      int64
+}
+
+func newDecodeDiskUsageState(topoInfo *master_pb.TopologyInfo, diskType types.DiskType) *decodeDiskUsageState {
+	state := &decodeDiskUsageState{byNode: make(map[pb.ServerAddress]*decodeDiskUsageCounts)}
+	eachDataNode(topoInfo, func(dc DataCenterId, rack RackId, dn *master_pb.DataNodeInfo) {
+		if diskInfo, found := dn.DiskInfos[string(diskType)]; found {
+			state.byNode[pb.NewServerAddressFromDataNode(dn)] = &decodeDiskUsageCounts{
+				maxVolumeCount:    diskInfo.MaxVolumeCount,
+				volumeCount:       diskInfo.VolumeCount,
+				remoteVolumeCount: diskInfo.RemoteVolumeCount,
+				ecShardCount:      int64(countShards(diskInfo.EcShardInfos)),
+			}
+		}
+	})
+	return state
+}
+
+func (state *decodeDiskUsageState) freeVolumeCount(location pb.ServerAddress) (int64, bool) {
+	if state == nil {
+		return 0, false
+	}
+	usage, found := state.byNode[location]
+	if !found {
+		return 0, false
+	}
+	free := usage.maxVolumeCount - (usage.volumeCount - usage.remoteVolumeCount)
+	free -= (usage.ecShardCount + int64(erasure_coding.DataShardsCount) - 1) / int64(erasure_coding.DataShardsCount)
+	return free, true
+}
+
+func (state *decodeDiskUsageState) applyDecode(targetNodeLocation pb.ServerAddress, shardCounts map[pb.ServerAddress]int, createdVolume bool) {
+	if state == nil {
+		return
+	}
+	for location, shardCount := range shardCounts {
+		if usage, found := state.byNode[location]; found {
+			usage.ecShardCount -= int64(shardCount)
+		}
+	}
+	if createdVolume {
+		if usage, found := state.byNode[targetNodeLocation]; found {
+			usage.volumeCount++
+		}
+	}
+}