snapshot of https://github.com/seaweedfs/seaweedfs.git (master, 2026-09-16; blobs > 131072B omitted)

weed/util/chunk_cache/chunk_cache_on_disk.go

@@ -0,0 +1,235 @@
+package chunk_cache
+
+import (
+	"fmt"
+	"os"
+	"time"
+
+	"github.com/syndtr/goleveldb/leveldb/opt"
+
+	"github.com/seaweedfs/seaweedfs/weed/glog"
+	"github.com/seaweedfs/seaweedfs/weed/storage"
+	"github.com/seaweedfs/seaweedfs/weed/storage/backend"
+	"github.com/seaweedfs/seaweedfs/weed/storage/needle"
+	"github.com/seaweedfs/seaweedfs/weed/storage/types"
+	"github.com/seaweedfs/seaweedfs/weed/util"
+)
+
+// This implements an on disk cache
+// The entries are an FIFO with a size limit
+
+type ChunkCacheVolume struct {
+	DataBackend backend.BackendStorageFile
+	nm          storage.NeedleMapper
+	fileName    string
+	smallBuffer []byte
+	sizeLimit   int64
+	lastModTime time.Time
+	fileSize    int64
+}
+
+func LoadOrCreateChunkCacheVolume(fileName string, preallocate int64) (*ChunkCacheVolume, error) {
+
+	v := &ChunkCacheVolume{
+		smallBuffer: make([]byte, types.NeedlePaddingSize),
+		fileName:    fileName,
+		sizeLimit:   preallocate,
+	}
+
+	var err error
+	var indexFile *os.File
+
+	defer func() {
+		if err != nil {
+			if v.DataBackend != nil {
+				v.DataBackend.Close()
+			}
+			if indexFile != nil {
+				indexFile.Close()
+			}
+		}
+	}()
+
+	if exists, canRead, canWrite, modTime, fileSize := util.CheckFile(v.fileName + ".dat"); exists {
+		if !canRead {
+			return nil, fmt.Errorf("cannot read cache file %s.dat", v.fileName)
+		}
+		if !canWrite {
+			return nil, fmt.Errorf("cannot write cache file %s.dat", v.fileName)
+		}
+		var dataFile *os.File
+		if dataFile, err = os.OpenFile(v.fileName+".dat", os.O_RDWR|os.O_CREATE, 0644); err != nil {
+			return nil, fmt.Errorf("cannot create cache file %s.dat: %v", v.fileName, err)
+		}
+		v.DataBackend = backend.NewDiskFile(dataFile)
+		v.lastModTime = modTime
+		v.fileSize = fileSize
+	} else {
+		if v.DataBackend, err = backend.CreateVolumeFile(v.fileName+".dat", preallocate, 0); err != nil {
+			return nil, fmt.Errorf("cannot create cache file %s.dat: %v", v.fileName, err)
+		}
+		v.lastModTime = time.Now()
+	}
+
+	if indexFile, err = os.OpenFile(v.fileName+".idx", os.O_RDWR|os.O_CREATE, 0644); err != nil {
+		return nil, fmt.Errorf("cannot write cache index %s.idx: %v", v.fileName, err)
+	}
+
+	glog.V(1).Infoln("loading leveldb", v.fileName+".ldb")
+	opts := &opt.Options{
+		BlockCacheCapacity:            2 * 1024 * 1024, // default value is 8MiB
+		WriteBuffer:                   1 * 1024 * 1024, // default value is 4MiB
+		CompactionTableSizeMultiplier: 10,              // default value is 1
+	}
+	if v.nm, err = storage.NewLevelDbNeedleMap(v.fileName+".ldb", indexFile, opts, 0, needle.GetCurrentVersion()); err != nil {
+		return nil, fmt.Errorf("loading leveldb %s error: %v", v.fileName+".ldb", err)
+	}
+
+	return v, nil
+
+}
+
+func (v *ChunkCacheVolume) Shutdown() {
+	if v.DataBackend != nil {
+		v.DataBackend.Close()
+		v.DataBackend = nil
+	}
+	if v.nm != nil {
+		v.nm.Close()
+		v.nm = nil
+	}
+}
+
+func (v *ChunkCacheVolume) doReset() {
+	v.Shutdown()
+	fn := v.fileName + ".dat"
+	err := os.Truncate(fn, 0)
+	if err != nil {
+		glog.Errorf("ChunkCacheVolume.doReset: truncate %q failed: %s", fn, err)
+	}
+	fn = v.fileName + ".idx"
+	err = os.Truncate(fn, 0)
+	if err != nil {
+		glog.Errorf("ChunkCacheVolume.doReset: truncate %q failed: %s", fn, err)
+	}
+	fn = v.fileName + ".ldb"
+	err = os.RemoveAll(fn)
+	if err != nil {
+		glog.Errorf("ChunkCacheVolume.doReset: remove %q failed: %s", fn, err)
+	} else {
+		glog.V(4).Infof("cache removed %s", fn)
+	}
+}
+
+func (v *ChunkCacheVolume) Reset() (*ChunkCacheVolume, error) {
+	v.doReset()
+	return LoadOrCreateChunkCacheVolume(v.fileName, v.sizeLimit)
+}
+
+// minFadviseSize is the minimum read size (in bytes) before we call fadvise
+// DONTNEED. For small reads the syscall overhead outweighs the benefit, and
+// the kernel's page cache may serve the data again sooner than we think.
+const minFadviseSize = 1 << 20 // 1 MiB
+
+// dropReadCache advises the kernel to drop page cache for the byte range
+// just read. This is best-effort; failures are logged at V(4).
+// Only applied for reads >= minFadviseSize to avoid syscall overhead on
+// small needle reads where the kernel page cache is more beneficial.
+func (v *ChunkCacheVolume) dropReadCache(offset int64, length int64) {
+	if length < minFadviseSize {
+		return
+	}
+	type fdProvider interface {
+		Fd() uintptr
+	}
+	if fp, ok := v.DataBackend.(fdProvider); ok {
+		fd := int(fp.Fd())
+		if fd < 0 {
+			return
+		}
+		if err := util.DropOSPageCache(fd, offset, length); err != nil {
+			glog.V(4).Infof("fadvise DONTNEED %s offset %d len %d: %v", v.fileName, offset, length, err)
+		}
+	}
+}
+
+func (v *ChunkCacheVolume) GetNeedle(key types.NeedleId) ([]byte, error) {
+
+	nv, ok := v.nm.Get(key)
+	if !ok {
+		return nil, storage.ErrorNotFound
+	}
+	data := make([]byte, nv.Size)
+	readOffset := nv.Offset.ToActualOffset()
+	if readSize, readErr := v.DataBackend.ReadAt(data, readOffset); readErr != nil {
+		if readSize != int(nv.Size) {
+			return nil, fmt.Errorf("read %s.dat [%d,%d): %v",
+				v.fileName, readOffset, readOffset+int64(nv.Size), readErr)
+		}
+	} else {
+		if readSize != int(nv.Size) {
+			return nil, fmt.Errorf("read %d, expected %d", readSize, nv.Size)
+		}
+	}
+
+	v.dropReadCache(readOffset, int64(nv.Size))
+	return data, nil
+}
+
+func (v *ChunkCacheVolume) readNeedleSliceAt(data []byte, key types.NeedleId, offset uint64) (n int, err error) {
+	nv, ok := v.nm.Get(key)
+	if !ok {
+		return 0, storage.ErrorNotFound
+	}
+	wanted := min(len(data), int(nv.Size)-int(offset))
+	if wanted < 0 {
+		// should never happen, but better than panicking
+		return 0, ErrorOutOfBounds
+	}
+	readOffset := nv.Offset.ToActualOffset() + int64(offset)
+	if n, err = v.DataBackend.ReadAt(data[:wanted], readOffset); err != nil {
+		if n != wanted {
+			return n, fmt.Errorf("read %s.dat [%d,%d): %v",
+				v.fileName, readOffset, int64(readOffset)+int64(wanted), err)
+		}
+	} else {
+		if n != wanted {
+			return n, fmt.Errorf("read %d, expected %d", n, wanted)
+		}
+	}
+	if err != nil && n == wanted {
+		err = nil
+	}
+	if n > 0 {
+		v.dropReadCache(readOffset, int64(n))
+	}
+	return n, err
+}
+
+func (v *ChunkCacheVolume) WriteNeedle(key types.NeedleId, data []byte) error {
+
+	offset := v.fileSize
+
+	written, err := v.DataBackend.WriteAt(data, offset)
+	if err != nil {
+		return err
+	} else if written != len(data) {
+		return fmt.Errorf("partial written %d, expected %d", written, len(data))
+	}
+
+	v.fileSize += int64(written)
+	extraSize := written % types.NeedlePaddingSize
+	if extraSize != 0 {
+		_, err = v.DataBackend.WriteAt(v.smallBuffer[:types.NeedlePaddingSize-extraSize], offset+int64(written))
+		if err != nil {
+			return err
+		}
+		v.fileSize += int64(types.NeedlePaddingSize - extraSize)
+	}
+
+	if err := v.nm.Put(key, types.ToOffset(offset), types.Size(len(data))); err != nil {
+		return err
+	}
+
+	return nil
+}