seaweedfs/weed/server/volume_grpc_erasure_coding.go

package weed_server

import (
	"context"
	"fmt"
	"io"
	"math"
	"os"
	"path"
	"strconv"
	"strings"
	"time"

	"github.com/seaweedfs/seaweedfs/weed/glog"
	"github.com/seaweedfs/seaweedfs/weed/operation"
	"github.com/seaweedfs/seaweedfs/weed/pb"
	"github.com/seaweedfs/seaweedfs/weed/pb/volume_server_pb"
	"github.com/seaweedfs/seaweedfs/weed/storage"
	"github.com/seaweedfs/seaweedfs/weed/storage/erasure_coding"
	"github.com/seaweedfs/seaweedfs/weed/storage/needle"
	"github.com/seaweedfs/seaweedfs/weed/storage/types"
	"github.com/seaweedfs/seaweedfs/weed/storage/volume_info"
	"github.com/seaweedfs/seaweedfs/weed/util"

	"google.golang.org/grpc/codes"
	"google.golang.org/grpc/status"
)

/*

Steps to apply erasure coding to .dat .idx files
0. ensure the volume is readonly
1. client call VolumeEcShardsGenerate to generate the .ecx and .ec00 ~ .ec13 files
2. client ask master for possible servers to hold the ec files
3. client call VolumeEcShardsCopy on above target servers to copy ec files from the source server
4. target servers report the new ec files to the master
5.   master stores vid -> [14]*DataNode
6. client checks master. If all 14 slices are ready, delete the original .idx, .idx files

*/

// VolumeEcShardsGenerate generates the .ecx and .ec00 ~ .ec13 files
func (vs *VolumeServer) VolumeEcShardsGenerate(ctx context.Context, req *volume_server_pb.VolumeEcShardsGenerateRequest) (*volume_server_pb.VolumeEcShardsGenerateResponse, error) {
	if err := vs.CheckMaintenanceMode(); err != nil {
		return nil, err
	}

	glog.V(0).Infof("VolumeEcShardsGenerate: %v", req)

	v := vs.store.GetVolume(needle.VolumeId(req.VolumeId))
	if v == nil {
		return nil, fmt.Errorf("volume %d not found", req.VolumeId)
	}
	baseFileName := v.DataFileName()

	if v.Collection != req.Collection {
		return nil, fmt.Errorf("existing collection:%v unexpected input: %v", v.Collection, req.Collection)
	}

	// Create EC context - prefer existing .vif config if present (for regeneration scenarios)
	ecCtx := erasure_coding.NewDefaultECContext(req.Collection, needle.VolumeId(req.VolumeId))
	if volumeInfo, _, found, _ := volume_info.MaybeLoadVolumeInfo(baseFileName + ".vif"); found && volumeInfo.EcShardConfig != nil {
		ds := int(volumeInfo.EcShardConfig.DataShards)
		ps := int(volumeInfo.EcShardConfig.ParityShards)

		// Validate and use existing EC config
		if ds > 0 && ps > 0 && ds+ps <= erasure_coding.MaxShardCount {
			ecCtx.DataShards = ds
			ecCtx.ParityShards = ps
			glog.V(0).Infof("Using existing EC config for volume %d: %s", req.VolumeId, ecCtx.String())
		} else {
			glog.Warningf("Invalid EC config in .vif for volume %d (data=%d, parity=%d), using defaults", req.VolumeId, ds, ps)
		}
	} else {
		glog.V(0).Infof("Using default EC config for volume %d: %s", req.VolumeId, ecCtx.String())
	}

	shouldCleanup := true
	defer func() {
		if !shouldCleanup {
			return
		}
		for i := 0; i < ecCtx.Total(); i++ {
			os.Remove(baseFileName + ecCtx.ToExt(i))
		}
		os.Remove(v.IndexFileName() + ".ecx")
	}()

	// IMPORTANT: Generate .ecx BEFORE EC shards to prevent a race condition.
	// If .ecx were generated after EC shards, any write (e.g. from WriteNeedleBlob
	// during replica sync) between the two steps would add entries to .idx that
	// end up in .ecx but whose data is NOT in the EC shards — causing "shard too
	// short" and "size mismatch" errors on reads.
	//
	// By generating .ecx first, it reflects the .idx state at or before the .dat
	// is read for EC encoding. If a write sneaks in after .ecx but before/during
	// EC encoding, the shards contain MORE data than .ecx references, which is
	// harmless (the extra data is simply not indexed).

	// write .ecx file from the current .idx
	if err := erasure_coding.WriteSortedFileFromIdx(v.IndexFileName(), ".ecx"); err != nil {
		return nil, fmt.Errorf("WriteSortedFileFromIdx %s: %v", v.IndexFileName(), err)
	}

	// snapshot .dat file size before encoding — must match what .ecx references
	datSize, _, _ := v.FileStat()

	// write .ec00 ~ .ec[TotalShards-1] files using context
	if err := erasure_coding.WriteEcFilesWithContext(baseFileName, ecCtx); err != nil {
		return nil, fmt.Errorf("WriteEcFilesWithContext %s: %v", baseFileName, err)
	}

	// write .vif files
	var expireAtSec uint64
	if v.Ttl != nil {
		ttlSecond := v.Ttl.ToSeconds()
		if ttlSecond > 0 {
			expireAtSec = uint64(time.Now().Unix()) + ttlSecond //calculated expiration time
		}
	}
	volumeInfo := &volume_server_pb.VolumeInfo{Version: uint32(v.Version())}
	volumeInfo.ExpireAtSec = expireAtSec
	volumeInfo.DatFileSize = int64(datSize)

	// Validate EC configuration before saving to .vif
	if ecCtx.DataShards <= 0 || ecCtx.ParityShards <= 0 || ecCtx.Total() > erasure_coding.MaxShardCount {
		return nil, fmt.Errorf("invalid EC config before saving: data=%d, parity=%d, total=%d (max=%d)",
			ecCtx.DataShards, ecCtx.ParityShards, ecCtx.Total(), erasure_coding.MaxShardCount)
	}

	// Save EC configuration to VolumeInfo
	volumeInfo.EcShardConfig = &volume_server_pb.EcShardConfig{
		DataShards:   uint32(ecCtx.DataShards),
		ParityShards: uint32(ecCtx.ParityShards),
	}
	glog.V(1).Infof("Saving EC config to .vif for volume %d: %d+%d (total: %d)",
		req.VolumeId, ecCtx.DataShards, ecCtx.ParityShards, ecCtx.Total())

	if err := volume_info.SaveVolumeInfo(baseFileName+".vif", volumeInfo); err != nil {
		return nil, fmt.Errorf("SaveVolumeInfo %s: %v", baseFileName, err)
	}

	shouldCleanup = false

	return &volume_server_pb.VolumeEcShardsGenerateResponse{}, nil
}

// VolumeEcShardsRebuild generates the any of the missing .ec00 ~ .ec13 files
func (vs *VolumeServer) VolumeEcShardsRebuild(ctx context.Context, req *volume_server_pb.VolumeEcShardsRebuildRequest) (*volume_server_pb.VolumeEcShardsRebuildResponse, error) {
	if err := vs.CheckMaintenanceMode(); err != nil {
		return nil, err
	}

	glog.V(0).Infof("VolumeEcShardsRebuild: %v", req)
	baseFileName := erasure_coding.EcShardBaseFileName(req.Collection, int(req.VolumeId))

	var rebuiltShardIds []uint32

	// Find the rebuild location: the location with the most shards and an .ecx file.
	// With multi-disk servers, shards may be spread across different locations.
	var rebuildLocation *storage.DiskLocation
	var rebuildShardCount int
	var otherLocationsWithShards []*storage.DiskLocation

	for _, location := range vs.store.Locations {
		_, _, existingShardCount, err := checkEcVolumeStatus(baseFileName, location)
		if err != nil {
			return nil, err
		}

		indexBaseFileName := path.Join(location.IdxDirectory, baseFileName)
		if !util.FileExists(indexBaseFileName+".ecx") && location.IdxDirectory != location.Directory {
			indexBaseFileName = path.Join(location.Directory, baseFileName)
		}
		hasEcx := util.FileExists(indexBaseFileName + ".ecx")

		// Skip locations that have neither shard files nor an .ecx file.
		if existingShardCount == 0 && !hasEcx {
			continue
		}

		if hasEcx && (rebuildLocation == nil || existingShardCount > rebuildShardCount) {
			if rebuildLocation != nil {
				otherLocationsWithShards = append(otherLocationsWithShards, rebuildLocation)
			}
			rebuildLocation = location
			rebuildShardCount = existingShardCount
		} else {
			otherLocationsWithShards = append(otherLocationsWithShards, location)
		}
	}

	if rebuildLocation == nil {
		return &volume_server_pb.VolumeEcShardsRebuildResponse{}, nil
	}

	// Collect additional directories where shard files may exist.
	// On multi-disk servers, existing local shards may be on a different disk
	// than where copied shards were placed during ec.rebuild.
	rebuildDataDir := rebuildLocation.Directory
	var additionalDirs []string
	for _, otherLocation := range otherLocationsWithShards {
		additionalDirs = append(additionalDirs, otherLocation.Directory)
	}

	// Rebuild missing EC files, searching all disk locations for input shards
	dataBaseFileName := path.Join(rebuildDataDir, baseFileName)
	if generatedShardIds, err := erasure_coding.RebuildEcFiles(dataBaseFileName, additionalDirs...); err != nil {
		return nil, fmt.Errorf("RebuildEcFiles %s: %v", dataBaseFileName, err)
	} else {
		rebuiltShardIds = generatedShardIds
	}

	indexBaseFileName := path.Join(rebuildLocation.IdxDirectory, baseFileName)
	if !util.FileExists(indexBaseFileName+".ecx") && rebuildLocation.IdxDirectory != rebuildLocation.Directory {
		indexBaseFileName = path.Join(rebuildLocation.Directory, baseFileName)
	}
	if err := erasure_coding.RebuildEcxFile(indexBaseFileName); err != nil {
		return nil, fmt.Errorf("RebuildEcxFile %s: %v", indexBaseFileName, err)
	}

	return &volume_server_pb.VolumeEcShardsRebuildResponse{
		RebuiltShardIds: rebuiltShardIds,
	}, nil
}

// VolumeEcShardsCopy copy the .ecx and some ec data slices
func (vs *VolumeServer) VolumeEcShardsCopy(ctx context.Context, req *volume_server_pb.VolumeEcShardsCopyRequest) (*volume_server_pb.VolumeEcShardsCopyResponse, error) {
	if err := vs.CheckMaintenanceMode(); err != nil {
		return nil, err
	}

	glog.V(0).Infof("VolumeEcShardsCopy: %v", req)

	var location *storage.DiskLocation

	// Select the target location for storing EC shard files.
	//
	// When req.DiskId > 0 the caller is explicitly choosing a disk:
	//   location = vs.store.Locations[req.DiskId]
	//   (DiskId=1 → Locations[1], DiskId=2 → Locations[2], etc.)
	//
	// When req.DiskId == 0 (the protobuf default, meaning "not specified")
	// we auto-select location by preferring the disk that already holds EC
	// shards for this volume, then falling back to any HDD, then any disk.
	//
	// Note: Locations[0] cannot be targeted explicitly via DiskId because 0
	// is indistinguishable from "unset". It can still be chosen by the
	// auto-select logic.
	if req.DiskId > 0 {
		// Validate disk ID is within bounds
		if int(req.DiskId) >= len(vs.store.Locations) {
			return nil, fmt.Errorf("invalid disk_id %d: only have %d disks", req.DiskId, len(vs.store.Locations))
		}

		// Use the specific disk location
		location = vs.store.Locations[req.DiskId]
		glog.V(1).Infof("Using disk %d for EC shard copy: %s", req.DiskId, location.Directory)
	} else {
		// Auto-select the target disk: prefer a disk that already has the
		// EC volume mounted, then a disk that owns the .ecx on disk (the
		// volume hasn't been mounted yet — relevant for ec.rebuild, where
		// only the first shard carries .ecx and subsequent shards must
		// land on the same disk; see #9212), then any HDD, then any disk.
		// Pass the build's default data-shard count for free-slot maths;
		// the helper takes it as a parameter so custom-ratio builds (e.g.
		// enterprise) can swap it without touching this file.
		location = vs.store.FindEcShardTargetLocation(req.Collection, needle.VolumeId(req.VolumeId), erasure_coding.DataShardsCount)
		if location == nil {
			return nil, fmt.Errorf("no space left")
		}
	}

	dataBaseFileName := storage.VolumeFileName(location.Directory, req.Collection, int(req.VolumeId))
	indexBaseFileName := storage.VolumeFileName(location.IdxDirectory, req.Collection, int(req.VolumeId))

	err := operation.WithVolumeServerClient(true, pb.ServerAddress(req.SourceDataNode), vs.grpcDialOption, func(client volume_server_pb.VolumeServerClient) error {

		// copy ec data slices
		for _, shardId := range req.ShardIds {
			if _, err := vs.doCopyFile(client, true, req.Collection, req.VolumeId, math.MaxUint32, math.MaxInt64, dataBaseFileName, erasure_coding.ToExt(int(shardId)), false, false, nil); err != nil {
				return err
			}
		}

		if req.CopyEcxFile {

			// copy ecx file
			if _, err := vs.doCopyFile(client, true, req.Collection, req.VolumeId, math.MaxUint32, math.MaxInt64, indexBaseFileName, ".ecx", false, false, nil); err != nil {
				return err
			}
		}

		if req.CopyEcjFile {
			// copy ecj file
			if _, err := vs.doCopyFile(client, true, req.Collection, req.VolumeId, math.MaxUint32, math.MaxInt64, indexBaseFileName, ".ecj", true, true, nil); err != nil {
				return err
			}
		}

		if req.CopyVifFile {
			// copy vif file
			if _, err := vs.doCopyFile(client, true, req.Collection, req.VolumeId, math.MaxUint32, math.MaxInt64, dataBaseFileName, ".vif", false, true, nil); err != nil {
				return err
			}
		}
		return nil
	})
	if err != nil {
		return nil, fmt.Errorf("VolumeEcShardsCopy volume %d: %v", req.VolumeId, err)
	}

	return &volume_server_pb.VolumeEcShardsCopyResponse{}, nil
}

// VolumeEcShardsDelete local delete the .ecx and some ec data slices if not needed
// the shard should not be mounted before calling this.
func (vs *VolumeServer) VolumeEcShardsDelete(ctx context.Context, req *volume_server_pb.VolumeEcShardsDeleteRequest) (*volume_server_pb.VolumeEcShardsDeleteResponse, error) {
	if err := vs.checkGrpcAdminAuth(ctx); err != nil {
		return nil, err
	}
	if err := vs.CheckMaintenanceMode(); err != nil {
		return nil, err
	}

	bName := erasure_coding.EcShardBaseFileName(req.Collection, int(req.VolumeId))

	glog.V(0).Infof("ec volume %s shard delete %v", bName, req.ShardIds)

	for _, location := range vs.store.Locations {
		if err := deleteEcShardIdsForEachLocation(bName, location, req.ShardIds); err != nil {
			glog.Errorf("deleteEcShards from %s %s.%v: %v", location.Directory, bName, req.ShardIds, err)
			return nil, err
		}
	}

	return &volume_server_pb.VolumeEcShardsDeleteResponse{}, nil
}

func deleteEcShardIdsForEachLocation(bName string, location *storage.DiskLocation, shardIds []uint32) error {

	found := false

	indexBaseFilename := path.Join(location.IdxDirectory, bName)
	dataBaseFilename := path.Join(location.Directory, bName)

	ecxExists := util.FileExists(path.Join(location.IdxDirectory, bName+".ecx"))
	if !ecxExists && location.IdxDirectory != location.Directory {
		ecxExists = util.FileExists(path.Join(location.Directory, bName+".ecx"))
	}
	if ecxExists {
		for _, shardId := range shardIds {
			shardFileName := dataBaseFilename + erasure_coding.ToExt(int(shardId))
			if util.FileExists(shardFileName) {
				found = true
				os.Remove(shardFileName)
			}
		}
	}

	if !found {
		return nil
	}

	hasEcxFile, hasIdxFile, existingShardCount, err := checkEcVolumeStatus(bName, location)
	if err != nil {
		return err
	}

	if hasEcxFile && existingShardCount == 0 {
		// Remove .ecx/.ecj from both idx and data directories
		// since they may be in either location depending on when -dir.idx was configured
		if err := os.Remove(indexBaseFilename + ".ecx"); err != nil && !os.IsNotExist(err) {
			return err
		}
		os.Remove(indexBaseFilename + ".ecj")
		if location.IdxDirectory != location.Directory {
			os.Remove(dataBaseFilename + ".ecx")
			os.Remove(dataBaseFilename + ".ecj")
		}

		if !hasIdxFile {
			// .vif is used for ec volumes and normal volumes
			os.Remove(dataBaseFilename + ".vif")
		}
	}

	return nil
}

func checkEcVolumeStatus(bName string, location *storage.DiskLocation) (hasEcxFile bool, hasIdxFile bool, existingShardCount int, err error) {
	// check whether to delete the .ecx and .ecj file also
	fileInfos, err := os.ReadDir(location.Directory)
	if err != nil {
		return false, false, 0, err
	}
	if location.IdxDirectory != location.Directory {
		idxFileInfos, err := os.ReadDir(location.IdxDirectory)
		if err != nil {
			return false, false, 0, err
		}
		fileInfos = append(fileInfos, idxFileInfos...)
	}
	for _, fileInfo := range fileInfos {
		if fileInfo.Name() == bName+".ecx" || fileInfo.Name() == bName+".ecj" {
			hasEcxFile = true
			continue
		}
		if fileInfo.Name() == bName+".idx" {
			hasIdxFile = true
			continue
		}
		if isEcDataShardFile(fileInfo.Name(), bName) {
			existingShardCount++
		}
	}
	return hasEcxFile, hasIdxFile, existingShardCount, nil
}

func isEcDataShardFile(fileName, baseName string) bool {
	const ecDataShardSuffixLen = 2 // ".ecNN"
	prefix := baseName + ".ec"
	if !strings.HasPrefix(fileName, prefix) {
		return false
	}
	suffix := strings.TrimPrefix(fileName, prefix)
	if len(suffix) != ecDataShardSuffixLen {
		return false
	}
	shardId, err := strconv.Atoi(suffix)
	if err != nil {
		return false
	}
	return shardId >= 0 && shardId < erasure_coding.MaxShardCount
}

func (vs *VolumeServer) VolumeEcShardsMount(ctx context.Context, req *volume_server_pb.VolumeEcShardsMountRequest) (*volume_server_pb.VolumeEcShardsMountResponse, error) {

	glog.V(0).Infof("VolumeEcShardsMount: %v", req)

	for _, shardId := range req.ShardIds {
		err := vs.store.MountEcShards(req.Collection, needle.VolumeId(req.VolumeId), erasure_coding.ShardId(shardId))

		if err != nil {
			glog.Errorf("ec shard mount %v: %v", req, err)
		} else {
			glog.V(2).Infof("ec shard mount %v", req)
		}

		if err != nil {
			return nil, fmt.Errorf("mount %d.%d: %v", req.VolumeId, shardId, err)
		}
	}

	return &volume_server_pb.VolumeEcShardsMountResponse{}, nil
}

func (vs *VolumeServer) VolumeEcShardsUnmount(ctx context.Context, req *volume_server_pb.VolumeEcShardsUnmountRequest) (*volume_server_pb.VolumeEcShardsUnmountResponse, error) {

	glog.V(0).Infof("VolumeEcShardsUnmount: %v", req)

	for _, shardId := range req.ShardIds {
		err := vs.store.UnmountEcShards(needle.VolumeId(req.VolumeId), erasure_coding.ShardId(shardId))

		if err != nil {
			glog.Errorf("ec shard unmount %v: %v", req, err)
		} else {
			glog.V(2).Infof("ec shard unmount %v", req)
		}

		if err != nil {
			return nil, fmt.Errorf("unmount %d.%d: %v", req.VolumeId, shardId, err)
		}
	}

	return &volume_server_pb.VolumeEcShardsUnmountResponse{}, nil
}

func (vs *VolumeServer) VolumeEcShardRead(req *volume_server_pb.VolumeEcShardReadRequest, stream volume_server_pb.VolumeServer_VolumeEcShardReadServer) error {

	ecVolume, found := vs.store.FindEcVolume(needle.VolumeId(req.VolumeId))
	if !found {
		return fmt.Errorf("VolumeEcShardRead not found ec volume id %d", req.VolumeId)
	}
	ecShard, found := ecVolume.FindEcVolumeShard(erasure_coding.ShardId(req.ShardId))
	if !found {
		return fmt.Errorf("not found ec shard %d.%d", req.VolumeId, req.ShardId)
	}

	if req.FileKey != 0 {
		_, size, _ := ecVolume.FindNeedleFromEcx(types.Uint64ToNeedleId(req.FileKey))
		if size.IsDeleted() {
			return stream.Send(&volume_server_pb.VolumeEcShardReadResponse{
				IsDeleted: true,
			})
		}
	}

	bufSize := req.Size
	if bufSize > BufferSizeLimit {
		bufSize = BufferSizeLimit
	}
	buffer := make([]byte, bufSize)

	startOffset, bytesToRead := req.Offset, req.Size

	for bytesToRead > 0 {
		// min of bytesToRead and bufSize
		bufferSize := bufSize
		if bufferSize > bytesToRead {
			bufferSize = bytesToRead
		}
		bytesread, err := ecShard.ReadAt(buffer[0:bufferSize], startOffset)

		// println("read", ecShard.FileName(), "startOffset", startOffset, bytesread, "bytes, with target", bufferSize)
		if bytesread > 0 {

			if int64(bytesread) > bytesToRead {
				bytesread = int(bytesToRead)
			}
			err = stream.Send(&volume_server_pb.VolumeEcShardReadResponse{
				Data: buffer[:bytesread],
			})
			if err != nil {
				// println("sending", bytesread, "bytes err", err.Error())
				return err
			}

			startOffset += int64(bytesread)
			bytesToRead -= int64(bytesread)

		}

		if err != nil {
			if err != io.EOF {
				return err
			}
			return nil
		}

	}

	return nil

}

func (vs *VolumeServer) VolumeEcBlobDelete(ctx context.Context, req *volume_server_pb.VolumeEcBlobDeleteRequest) (*volume_server_pb.VolumeEcBlobDeleteResponse, error) {
	if err := vs.CheckMaintenanceMode(); err != nil {
		return nil, err
	}

	glog.V(0).Infof("VolumeEcBlobDelete: %v", req)

	resp := &volume_server_pb.VolumeEcBlobDeleteResponse{}

	for _, location := range vs.store.Locations {
		if localEcVolume, found := location.FindEcVolume(needle.VolumeId(req.VolumeId)); found {

			_, size, _, err := localEcVolume.LocateEcShardNeedle(types.NeedleId(req.FileKey), needle.Version(req.Version))
			if err != nil {
				return nil, fmt.Errorf("locate in local ec volume: %w", err)
			}
			if size.IsDeleted() {
				return resp, nil
			}

			err = localEcVolume.DeleteNeedleFromEcx(types.NeedleId(req.FileKey))
			if err != nil {
				return nil, err
			}

			break
		}
	}

	return resp, nil
}

// VolumeEcShardsToVolume generates the .idx, .dat files from .ecx, .ecj and .ec01 ~ .ec14 files
func (vs *VolumeServer) VolumeEcShardsToVolume(ctx context.Context, req *volume_server_pb.VolumeEcShardsToVolumeRequest) (*volume_server_pb.VolumeEcShardsToVolumeResponse, error) {
	if err := vs.CheckMaintenanceMode(); err != nil {
		return nil, err
	}

	glog.V(0).Infof("VolumeEcShardsToVolume: %v", req)

	// Collect all EC shards (NewEcVolume will load EC config from .vif into v.ECContext)
	// Use MaxShardCount (32) to support custom EC ratios up to 32 total shards
	tempShards := make([]string, erasure_coding.MaxShardCount)
	v, found := vs.store.CollectEcShards(needle.VolumeId(req.VolumeId), tempShards)
	if !found {
		return nil, fmt.Errorf("ec volume %d not found", req.VolumeId)
	}

	if v.Collection != req.Collection {
		return nil, fmt.Errorf("existing collection:%v unexpected input: %v", v.Collection, req.Collection)
	}

	// Use EC context (already loaded from .vif) to determine data shard count
	dataShards := v.ECContext.DataShards

	// Defensive validation to prevent panics from corrupted ECContext
	if dataShards <= 0 || dataShards > erasure_coding.MaxShardCount {
		return nil, fmt.Errorf("invalid data shard count %d for volume %d (must be 1..%d)", dataShards, req.VolumeId, erasure_coding.MaxShardCount)
	}

	shardFileNames := tempShards[:dataShards]
	glog.V(1).Infof("Using EC config from volume %d: %d data shards", req.VolumeId, dataShards)

	// Verify all data shards are present
	for shardId := 0; shardId < dataShards; shardId++ {
		if shardFileNames[shardId] == "" {
			return nil, fmt.Errorf("ec volume %d missing shard %d", req.VolumeId, shardId)
		}
	}

	dataBaseFileName, indexBaseFileName := v.DataBaseFileName(), v.IndexBaseFileName()
	if !util.FileExists(indexBaseFileName + ".ecx") {
		indexBaseFileName = dataBaseFileName
	}

	// Merge .ecj deletions into .ecx so that HasLiveNeedles and FindDatFileSize
	// see the full set of deleted needles. Without this, needles deleted after the
	// last ecx rebuild would still appear live, causing the decoded .dat to include
	// data that should be skipped and HasLiveNeedles to return a false positive.
	if err := erasure_coding.RebuildEcxFile(indexBaseFileName); err != nil {
		return nil, fmt.Errorf("RebuildEcxFile %s: %v", indexBaseFileName, err)
	}

	// If the EC index contains no live entries, decoding should be a no-op:
	// just allow the caller to purge EC shards and do not generate an empty normal volume.
	hasLive, err := erasure_coding.HasLiveNeedles(indexBaseFileName)
	if err != nil {
		return nil, fmt.Errorf("HasLiveNeedles %s: %w", indexBaseFileName, err)
	}
	if !hasLive {
		return nil, status.Errorf(codes.FailedPrecondition, "ec volume %d %s", req.VolumeId, erasure_coding.EcNoLiveEntriesSubstring)
	}

	// calculate .dat file size
	datFileSize, err := erasure_coding.FindDatFileSize(dataBaseFileName, indexBaseFileName)
	if err != nil {
		return nil, fmt.Errorf("FindDatFileSize %s: %v", dataBaseFileName, err)
	}

	// write .dat file from .ec00 ~ .ec09 files
	if err := erasure_coding.WriteDatFile(dataBaseFileName, datFileSize, shardFileNames); err != nil {
		return nil, fmt.Errorf("WriteDatFile %s: %v", dataBaseFileName, err)
	}

	// write .idx file from .ecx and .ecj files
	if err := erasure_coding.WriteIdxFileFromEcIndex(indexBaseFileName); err != nil {
		return nil, fmt.Errorf("WriteIdxFileFromEcIndex %s: %v", v.IndexBaseFileName(), err)
	}

	var volumeLocation *storage.DiskLocation
	for _, location := range vs.store.Locations {
		if candidate, found := location.FindEcVolume(needle.VolumeId(req.VolumeId)); found && candidate == v {
			volumeLocation = location
			break
		}
	}
	if volumeLocation == nil {
		return nil, fmt.Errorf("ec volume %d location not found for offline compaction", req.VolumeId)
	}

	if err := vs.store.CompactVolumeFiles(
		needle.VolumeId(req.VolumeId),
		v.Collection,
		volumeLocation,
		vs.needleMapKind,
		vs.ldbTimout,
		0,
		vs.compactionBytePerSecond,
	); err != nil {
		glog.Errorf("CompactVolumeFiles %s: %v", dataBaseFileName, err)
	}

	return &volume_server_pb.VolumeEcShardsToVolumeResponse{}, nil
}

func (vs *VolumeServer) VolumeEcShardsInfo(ctx context.Context, req *volume_server_pb.VolumeEcShardsInfoRequest) (*volume_server_pb.VolumeEcShardsInfoResponse, error) {
	glog.V(0).Infof("VolumeEcShardsInfo: volume %d", req.VolumeId)

	glog.V(0).Infof("VolumeEcStatus: %v", req)

	vid := needle.VolumeId(req.GetVolumeId())
	ecv, found := vs.store.FindEcVolume(vid)
	if !found {
		return nil, fmt.Errorf("VolumeEcStatus: EC volume %d not found", vid)
	}

	shardInfos := make([]*volume_server_pb.EcShardInfo, len(ecv.Shards))
	for i, s := range ecv.Shards {
		shardInfos[i] = s.ToEcShardInfo()
	}

	var files, filesDeleted, totalSize uint64
	err := ecv.WalkIndex(func(_ types.NeedleId, _ types.Offset, size types.Size) error {
		// deleted files are counted when computing EC volume sizes. this aligns with VolumeStatus(),
		// which reports the raw data backend file size, regardless of deleted files.
		totalSize += uint64(size.Raw())

		if size.IsDeleted() {
			filesDeleted++
		} else {
			files++
		}

		return nil
	})
	if err != nil {
		return nil, err
	}

	res := &volume_server_pb.VolumeEcShardsInfoResponse{
		EcShardInfos:     shardInfos,
		FileCount:        files,
		FileDeletedCount: filesDeleted,
		VolumeSize:       totalSize,
	}

	return res, nil
}