volume: sync volume file right before compaction

fix https://github.com/chrislusf/seaweedfs/issues/1237

weed/storage/backend/backend.go

@@ -19,6 +19,7 @@ type BackendStorageFile interface {
 	io.Closer
 	GetStat() (datSize int64, modTime time.Time, err error)
 	Name() string
+	Sync() error
 }
 
 type BackendStorage interface {

weed/storage/backend/disk_file.go

@@ -48,3 +48,7 @@ func (df *DiskFile) GetStat() (datSize int64, modTime time.Time, err error) {
 func (df *DiskFile) Name() string {
 	return df.fullFilePath
 }
+
+func (df *DiskFile) Sync() error {
+	return df.File.Sync()
+}

weed/storage/backend/memory_map/memory_map_backend.go

@@ -58,3 +58,7 @@ func (mmf *MemoryMappedFile) GetStat() (datSize int64, modTime time.Time, err er
 func (mmf *MemoryMappedFile) Name() string {
 	return mmf.mm.File.Name()
 }
+
+func (mm *MemoryMappedFile) Sync() error {
+	return nil
+}

weed/storage/backend/s3_backend/s3_backend.go

@@ -179,3 +179,7 @@ func (s3backendStorageFile S3BackendStorageFile) GetStat() (datSize int64, modTi
 func (s3backendStorageFile S3BackendStorageFile) Name() string {
 	return s3backendStorageFile.key
 }
+
+func (s3backendStorageFile S3BackendStorageFile) Sync() error {
+	return nil
+}

weed/storage/volume_vacuum.go

@@ -53,6 +53,9 @@ func (v *Volume) Compact(preallocate int64, compactionBytePerSecond int64) error
 	v.lastCompactIndexOffset = v.IndexFileSize()
 	v.lastCompactRevision = v.SuperBlock.CompactionRevision
 	glog.V(3).Infof("creating copies for volume %d ,last offset %d...", v.Id, v.lastCompactIndexOffset)
+	if err := v.DataBackend.Sync(); err != nil {
+		glog.V(0).Infof("compact fail to sync volume %d", v.Id)
+	}
 	return v.copyDataAndGenerateIndexFile(filePath+".cpd", filePath+".cpx", preallocate, compactionBytePerSecond)
 }
 
@@ -73,6 +76,9 @@ func (v *Volume) Compact2(preallocate int64, compactionBytePerSecond int64) erro
 	v.lastCompactIndexOffset = v.IndexFileSize()
 	v.lastCompactRevision = v.SuperBlock.CompactionRevision
 	glog.V(3).Infof("creating copies for volume %d ...", v.Id)
+	if err := v.DataBackend.Sync(); err != nil {
+		glog.V(0).Infof("compact2 fail to sync volume %d", v.Id)
+	}
 	return copyDataBasedOnIndexFile(filePath+".dat", filePath+".idx", filePath+".cpd", filePath+".cpx", v.SuperBlock, v.Version(), preallocate, compactionBytePerSecond)
 }
 
@@ -93,6 +99,9 @@ func (v *Volume) CommitCompact() error {
 	glog.V(3).Infof("Got volume %d committing lock...", v.Id)
 	v.nm.Close()
 	if v.DataBackend != nil {
+		if err := v.DataBackend.Sync(); err != nil {
+			glog.V(0).Infof("fail to sync volume %d", v.Id)
+		}
 		if err := v.DataBackend.Close(); err != nil {
 			glog.V(0).Infof("fail to close volume %d", v.Id)
 		}