better control for reader caching

weed/filer/filechunk_manifest.go

@@ -3,6 +3,7 @@ package filer
 import (
 	"bytes"
 	"fmt"
+	"github.com/chrislusf/seaweedfs/weed/util/mem"
 	"github.com/chrislusf/seaweedfs/weed/wdclient"
 	"io"
 	"math"
@@ -77,7 +78,9 @@ func ResolveOneChunkManifest(lookupFileIdFn wdclient.LookupFileIdFunctionType, c
 	}
 
 	// IsChunkManifest
-	data, err := fetchChunk(lookupFileIdFn, chunk.GetFileIdString(), chunk.CipherKey, chunk.IsCompressed)
+	data := mem.Allocate(int(chunk.Size))
+	defer mem.Free(data)
+	_, err := fetchChunk(data, lookupFileIdFn, chunk.GetFileIdString(), chunk.CipherKey, chunk.IsCompressed)
 	if err != nil {
 		return nil, fmt.Errorf("fail to read manifest %s: %v", chunk.GetFileIdString(), err)
 	}
@@ -92,38 +95,37 @@ func ResolveOneChunkManifest(lookupFileIdFn wdclient.LookupFileIdFunctionType, c
 }
 
 // TODO fetch from cache for weed mount?
-func fetchChunk(lookupFileIdFn wdclient.LookupFileIdFunctionType, fileId string, cipherKey []byte, isGzipped bool) ([]byte, error) {
+func fetchChunk(data []byte, lookupFileIdFn wdclient.LookupFileIdFunctionType, fileId string, cipherKey []byte, isGzipped bool) (int, error) {
 	urlStrings, err := lookupFileIdFn(fileId)
 	if err != nil {
 		glog.Errorf("operation LookupFileId %s failed, err: %v", fileId, err)
-		return nil, err
+		return 0, err
 	}
-	return retriedFetchChunkData(urlStrings, cipherKey, isGzipped, true, 0, 0)
+	return retriedFetchChunkData(data, urlStrings, cipherKey, isGzipped, true, 0)
 }
 
-func fetchChunkRange(lookupFileIdFn wdclient.LookupFileIdFunctionType, fileId string, cipherKey []byte, isGzipped bool, offset int64, size int) ([]byte, error) {
+func fetchChunkRange(data []byte, lookupFileIdFn wdclient.LookupFileIdFunctionType, fileId string, cipherKey []byte, isGzipped bool, offset int64) (int, error) {
 	urlStrings, err := lookupFileIdFn(fileId)
 	if err != nil {
 		glog.Errorf("operation LookupFileId %s failed, err: %v", fileId, err)
-		return nil, err
+		return 0, err
 	}
-	return retriedFetchChunkData(urlStrings, cipherKey, isGzipped, false, offset, size)
+	return retriedFetchChunkData(data, urlStrings, cipherKey, isGzipped, false, offset)
 }
 
-func retriedFetchChunkData(urlStrings []string, cipherKey []byte, isGzipped bool, isFullChunk bool, offset int64, size int) ([]byte, error) {
+func retriedFetchChunkData(buffer []byte, urlStrings []string, cipherKey []byte, isGzipped bool, isFullChunk bool, offset int64) (n int, err error) {
 
-	var err error
 	var shouldRetry bool
-	receivedData := make([]byte, 0, size)
 
 	for waitTime := time.Second; waitTime < util.RetryWaitTime; waitTime += waitTime / 2 {
 		for _, urlString := range urlStrings {
-			receivedData = receivedData[:0]
+			n = 0
 			if strings.Contains(urlString, "%") {
 				urlString = url.PathEscape(urlString)
 			}
-			shouldRetry, err = util.ReadUrlAsStream(urlString+"?readDeleted=true", cipherKey, isGzipped, isFullChunk, offset, size, func(data []byte) {
-				receivedData = append(receivedData, data...)
+			shouldRetry, err = util.ReadUrlAsStream(urlString+"?readDeleted=true", cipherKey, isGzipped, isFullChunk, offset, len(buffer), func(data []byte) {
+				x := copy(buffer[n:], data)
+				n += x
 			})
 			if !shouldRetry {
 				break
@@ -142,7 +144,7 @@ func retriedFetchChunkData(urlStrings []string, cipherKey []byte, isGzipped bool
 		}
 	}
 
-	return receivedData, err
+	return n, err
 
 }
 

weed/filer/reader_at.go

@@ -12,20 +12,14 @@ import (
 	"github.com/chrislusf/seaweedfs/weed/util"
 	"github.com/chrislusf/seaweedfs/weed/util/chunk_cache"
 	"github.com/chrislusf/seaweedfs/weed/wdclient"
-	"github.com/golang/groupcache/singleflight"
 )
 
 type ChunkReadAt struct {
 	masterClient  *wdclient.MasterClient
 	chunkViews    []*ChunkView
-	lookupFileId wdclient.LookupFileIdFunctionType
 	readerLock    sync.Mutex
 	fileSize      int64
-
-	fetchGroup      singleflight.Group
-	chunkCache      chunk_cache.ChunkCache
-	lastChunkFileId string
-	lastChunkData   []byte
+	readerCache   *ReaderCache
 	readerPattern *ReaderPattern
 }
 
@@ -90,16 +84,14 @@ func NewChunkReaderAtFromClient(lookupFn wdclient.LookupFileIdFunctionType, chun
 
 	return &ChunkReadAt{
 		chunkViews:    chunkViews,
-		lookupFileId:  lookupFn,
-		chunkCache:    chunkCache,
 		fileSize:      fileSize,
+		readerCache:   newReaderCache(5, chunkCache, lookupFn),
 		readerPattern: NewReaderPattern(),
 	}
 }
 
 func (c *ChunkReadAt) Close() error {
-	c.lastChunkData = nil
-	c.lastChunkFileId = ""
+	c.readerCache.destroy()
 	return nil
 }
 
@@ -142,16 +134,13 @@ func (c *ChunkReadAt) doReadAt(p []byte, offset int64) (n int, err error) {
 			continue
 		}
 		// glog.V(4).Infof("read [%d,%d), %d/%d chunk %s [%d,%d)", chunkStart, chunkStop, i, len(c.chunkViews), chunk.FileId, chunk.LogicOffset-chunk.Offset, chunk.LogicOffset-chunk.Offset+int64(chunk.Size))
-		var buffer []byte
 		bufferOffset := chunkStart - chunk.LogicOffset + chunk.Offset
-		bufferLength := chunkStop - chunkStart
-		buffer, err = c.readChunkSlice(chunk, nextChunk, uint64(bufferOffset), uint64(bufferLength))
+		copied, err := c.readChunkSliceAt(p[startOffset-offset:chunkStop-chunkStart+startOffset-offset], chunk, nextChunk, uint64(bufferOffset))
 		if err != nil {
 			glog.Errorf("fetching chunk %+v: %v\n", chunk, err)
-			return
+			return copied, err
 		}
 
-		copied := copy(p[startOffset-offset:chunkStop-chunkStart+startOffset-offset], buffer)
 		n += copied
 		startOffset, remaining = startOffset+int64(copied), remaining-int64(copied)
 	}
@@ -173,104 +162,15 @@ func (c *ChunkReadAt) doReadAt(p []byte, offset int64) (n int, err error) {
 
 }
 
-func (c *ChunkReadAt) readChunkSlice(chunkView *ChunkView, nextChunkViews *ChunkView, offset, length uint64) ([]byte, error) {
+func (c *ChunkReadAt) readChunkSliceAt(buffer []byte, chunkView *ChunkView, nextChunkViews *ChunkView, offset uint64) (n int, err error) {
 
-	var chunkSlice []byte
-	if chunkView.LogicOffset == 0 {
-		chunkSlice = c.chunkCache.GetChunkSlice(chunkView.FileId, offset, length)
-	}
-	if len(chunkSlice) > 0 {
-		return chunkSlice, nil
-	}
-	if c.lookupFileId == nil {
-		return nil, nil
-	}
 	if c.readerPattern.IsRandomMode() {
-		return c.doFetchRangeChunkData(chunkView, offset, length)
-	}
-	chunkData, err := c.readFromWholeChunkData(chunkView, nextChunkViews)
-	if err != nil {
-		return nil, err
+		return c.readerCache.ReadChunkAt(buffer, chunkView.FileId, chunkView.CipherKey, chunkView.IsGzipped, int64(offset), int(chunkView.ChunkSize), chunkView.LogicOffset == 0)
 	}
-	wanted := min(int64(length), int64(len(chunkData))-int64(offset))
-	return chunkData[offset : int64(offset)+wanted], nil
-}
 
-func (c *ChunkReadAt) readFromWholeChunkData(chunkView *ChunkView, nextChunkViews ...*ChunkView) (chunkData []byte, err error) {
-
-	if c.lastChunkFileId == chunkView.FileId {
-		return c.lastChunkData, nil
+	n, err = c.readerCache.ReadChunkAt(buffer, chunkView.FileId, chunkView.CipherKey, chunkView.IsGzipped, int64(offset), int(chunkView.ChunkSize), chunkView.LogicOffset == 0)
+	if nextChunkViews != nil {
+		c.readerCache.MaybeCache(nextChunkViews.FileId, nextChunkViews.CipherKey, nextChunkViews.IsGzipped, int(nextChunkViews.ChunkSize))
 	}
-
-	v, doErr := c.readOneWholeChunk(chunkView)
-
-	if doErr != nil {
-		return nil, doErr
-	}
-
-	chunkData = v.([]byte)
-
-	c.lastChunkData = chunkData
-	c.lastChunkFileId = chunkView.FileId
-
-	for _, nextChunkView := range nextChunkViews {
-		if c.chunkCache != nil && nextChunkView != nil {
-			go c.readOneWholeChunk(nextChunkView)
-		}
-	}
-
 	return
 }
-
-func (c *ChunkReadAt) readOneWholeChunk(chunkView *ChunkView) (interface{}, error) {
-
-	var err error
-
-	return c.fetchGroup.Do(chunkView.FileId, func() (interface{}, error) {
-
-		glog.V(4).Infof("readFromWholeChunkData %s offset %d [%d,%d) size at least %d", chunkView.FileId, chunkView.Offset, chunkView.LogicOffset, chunkView.LogicOffset+int64(chunkView.Size), chunkView.ChunkSize)
-
-		var data []byte
-		if chunkView.LogicOffset == 0 {
-			data = c.chunkCache.GetChunk(chunkView.FileId, chunkView.ChunkSize)
-		}
-		if data != nil {
-			glog.V(4).Infof("cache hit %s [%d,%d)", chunkView.FileId, chunkView.LogicOffset-chunkView.Offset, chunkView.LogicOffset-chunkView.Offset+int64(len(data)))
-		} else {
-			var err error
-			data, err = c.doFetchFullChunkData(chunkView)
-			if err != nil {
-				return data, err
-			}
-			if chunkView.LogicOffset == 0 {
-				// only cache the first chunk
-				c.chunkCache.SetChunk(chunkView.FileId, data)
-			}
-		}
-		return data, err
-	})
-}
-
-func (c *ChunkReadAt) doFetchFullChunkData(chunkView *ChunkView) ([]byte, error) {
-
-	glog.V(4).Infof("+ doFetchFullChunkData %s", chunkView.FileId)
-
-	data, err := fetchChunk(c.lookupFileId, chunkView.FileId, chunkView.CipherKey, chunkView.IsGzipped)
-
-	glog.V(4).Infof("- doFetchFullChunkData %s", chunkView.FileId)
-
-	return data, err
-
-}
-
-func (c *ChunkReadAt) doFetchRangeChunkData(chunkView *ChunkView, offset, length uint64) ([]byte, error) {
-
-	glog.V(4).Infof("+ doFetchFullChunkData %s", chunkView.FileId)
-
-	data, err := fetchChunkRange(c.lookupFileId, chunkView.FileId, chunkView.CipherKey, chunkView.IsGzipped, int64(offset), int(length))
-
-	glog.V(4).Infof("- doFetchFullChunkData %s", chunkView.FileId)
-
-	return data, err
-
-}

weed/filer/reader_at_test.go

@@ -21,8 +21,12 @@ func (m *mockChunkCache) GetChunk(fileId string, minSize uint64) (data []byte) {
 	return data
 }
 
-func (m *mockChunkCache) GetChunkSlice(fileId string, offset, length uint64) []byte {
-	return m.GetChunk(fileId, length)
+func (m *mockChunkCache) ReadChunkAt(data []byte, fileId string, offset uint64) (n int, err error) {
+	x, _ := strconv.Atoi(fileId)
+	for i := 0; i < len(data); i++ {
+		data[i] = byte(x)
+	}
+	return len(data), nil
 }
 
 func (m *mockChunkCache) SetChunk(fileId string, data []byte) {
@@ -65,10 +69,9 @@ func TestReaderAt(t *testing.T) {
 
 	readerAt := &ChunkReadAt{
 		chunkViews:    ViewFromVisibleIntervals(visibles, 0, math.MaxInt64),
-		lookupFileId:  nil,
 		readerLock:    sync.Mutex{},
 		fileSize:      10,
-		chunkCache:    &mockChunkCache{},
+		readerCache:   newReaderCache(3, &mockChunkCache{}, nil),
 		readerPattern: NewReaderPattern(),
 	}
 
@@ -116,10 +119,9 @@ func TestReaderAt0(t *testing.T) {
 
 	readerAt := &ChunkReadAt{
 		chunkViews:    ViewFromVisibleIntervals(visibles, 0, math.MaxInt64),
-		lookupFileId:  nil,
 		readerLock:    sync.Mutex{},
 		fileSize:      10,
-		chunkCache:    &mockChunkCache{},
+		readerCache:   newReaderCache(3, &mockChunkCache{}, nil),
 		readerPattern: NewReaderPattern(),
 	}
 
@@ -145,10 +147,9 @@ func TestReaderAt1(t *testing.T) {
 
 	readerAt := &ChunkReadAt{
 		chunkViews:    ViewFromVisibleIntervals(visibles, 0, math.MaxInt64),
-		lookupFileId:  nil,
 		readerLock:    sync.Mutex{},
 		fileSize:      20,
-		chunkCache:    &mockChunkCache{},
+		readerCache:   newReaderCache(3, &mockChunkCache{}, nil),
 		readerPattern: NewReaderPattern(),
 	}
 

weed/filer/reader_cache.go

@@ -0,0 +1,187 @@
+package filer
+
+import (
+	"fmt"
+	"github.com/chrislusf/seaweedfs/weed/glog"
+	"github.com/chrislusf/seaweedfs/weed/util/chunk_cache"
+	"github.com/chrislusf/seaweedfs/weed/util/mem"
+	"github.com/chrislusf/seaweedfs/weed/wdclient"
+	"sync"
+	"time"
+)
+
+type ReaderCache struct {
+	chunkCache     chunk_cache.ChunkCache
+	lookupFileIdFn wdclient.LookupFileIdFunctionType
+	sync.Mutex
+	downloaders map[string]*SingleChunkCacher
+	limit       int
+}
+
+type SingleChunkCacher struct {
+	sync.RWMutex
+	parent        *ReaderCache
+	chunkFileId   string
+	data          []byte
+	err           error
+	cipherKey     []byte
+	isGzipped     bool
+	chunkSize     int
+	shouldCache   bool
+	wg            sync.WaitGroup
+	completedTime time.Time
+}
+
+func newReaderCache(limit int, chunkCache chunk_cache.ChunkCache, lookupFileIdFn wdclient.LookupFileIdFunctionType) *ReaderCache {
+	return &ReaderCache{
+		limit:          limit,
+		chunkCache:     chunkCache,
+		lookupFileIdFn: lookupFileIdFn,
+		downloaders:    make(map[string]*SingleChunkCacher),
+	}
+}
+
+func (rc *ReaderCache) MaybeCache(fileId string, cipherKey []byte, isGzipped bool, chunkSize int) {
+	rc.Lock()
+	defer rc.Unlock()
+	if _, found := rc.downloaders[fileId]; found {
+		return
+	}
+	if rc.lookupFileIdFn == nil {
+		return
+	}
+
+	// if too many, delete one of them?
+	glog.V(0).Infof("downloader2 %d", len(rc.downloaders))
+	if len(rc.downloaders) >= rc.limit {
+		oldestFid, oldestTime := "", time.Now()
+		for fid, downloader := range rc.downloaders {
+			if !downloader.completedTime.IsZero() {
+				if downloader.completedTime.Before(oldestTime) {
+					oldestFid, oldestTime = fid, downloader.completedTime
+				}
+			}
+		}
+		if oldestFid != "" {
+			oldDownloader := rc.downloaders[oldestFid]
+			delete(rc.downloaders, oldestFid)
+			oldDownloader.destroy()
+		} else {
+			// if still no slots, return
+			return
+		}
+	}
+
+	cacher := newSingleChunkCacher(rc, fileId, cipherKey, isGzipped, chunkSize, false)
+	cacher.wg.Add(1)
+	go cacher.startCaching()
+	cacher.wg.Wait()
+	rc.downloaders[fileId] = cacher
+
+	return
+}
+
+func (rc *ReaderCache) ReadChunkAt(buffer []byte, fileId string, cipherKey []byte, isGzipped bool, offset int64, chunkSize int, shouldCache bool) (int, error) {
+	rc.Lock()
+	defer rc.Unlock()
+	if cacher, found := rc.downloaders[fileId]; found {
+		return cacher.readChunkAt(buffer, offset)
+	}
+	if shouldCache || rc.lookupFileIdFn == nil {
+		n, err := rc.chunkCache.ReadChunkAt(buffer, fileId, uint64(offset))
+		if n > 0 {
+			return n, err
+		}
+	}
+
+	glog.V(0).Infof("downloader1 %d", len(rc.downloaders))
+	if len(rc.downloaders) >= rc.limit {
+		oldestFid, oldestTime := "", time.Now()
+		for fid, downloader := range rc.downloaders {
+			if !downloader.completedTime.IsZero() {
+				if downloader.completedTime.Before(oldestTime) {
+					oldestFid, oldestTime = fid, downloader.completedTime
+				}
+			}
+		}
+		if oldestFid != "" {
+			oldDownloader := rc.downloaders[oldestFid]
+			delete(rc.downloaders, oldestFid)
+			oldDownloader.destroy()
+		}
+	}
+
+	cacher := newSingleChunkCacher(rc, fileId, cipherKey, isGzipped, chunkSize, shouldCache)
+	cacher.wg.Add(1)
+	go cacher.startCaching()
+	cacher.wg.Wait()
+	rc.downloaders[fileId] = cacher
+
+	return cacher.readChunkAt(buffer, offset)
+}
+
+func (rc *ReaderCache) destroy() {
+	rc.Lock()
+	defer rc.Unlock()
+
+	for _, downloader := range rc.downloaders {
+		downloader.destroy()
+	}
+
+}
+
+func newSingleChunkCacher(parent *ReaderCache, fileId string, cipherKey []byte, isGzipped bool, chunkSize int, shouldCache bool) *SingleChunkCacher {
+	t := &SingleChunkCacher{
+		parent:      parent,
+		chunkFileId: fileId,
+		cipherKey:   cipherKey,
+		isGzipped:   isGzipped,
+		chunkSize:   chunkSize,
+		shouldCache: shouldCache,
+	}
+	return t
+}
+
+func (s *SingleChunkCacher) startCaching() {
+	s.Lock()
+	defer s.Unlock()
+
+	s.wg.Done() // means this has been started
+
+	urlStrings, err := s.parent.lookupFileIdFn(s.chunkFileId)
+	if err != nil {
+		s.err = fmt.Errorf("operation LookupFileId %s failed, err: %v", s.chunkFileId, err)
+		return
+	}
+
+	s.data = mem.Allocate(s.chunkSize)
+
+	_, s.err = retriedFetchChunkData(s.data, urlStrings, s.cipherKey, s.isGzipped, true, 0)
+	if s.err != nil {
+		mem.Free(s.data)
+		s.data = nil
+		return
+	}
+
+	s.completedTime = time.Now()
+	if s.shouldCache {
+		s.parent.chunkCache.SetChunk(s.chunkFileId, s.data)
+	}
+
+	return
+}
+
+func (s *SingleChunkCacher) destroy() {
+	if s.data != nil {
+		mem.Free(s.data)
+		s.data = nil
+	}
+}
+
+func (s *SingleChunkCacher) readChunkAt(buf []byte, offset int64) (int, error) {
+	s.RLock()
+	defer s.RUnlock()
+
+	return copy(buf, s.data[offset:]), s.err
+
+}

weed/filer/stream.go

@@ -133,30 +133,30 @@ func writeZero(w io.Writer, size int64) (err error) {
 	return
 }
 
-func ReadAll(masterClient *wdclient.MasterClient, chunks []*filer_pb.FileChunk) ([]byte, error) {
-
-	buffer := bytes.Buffer{}
+func ReadAll(buffer []byte, masterClient *wdclient.MasterClient, chunks []*filer_pb.FileChunk) error {
 
 	lookupFileIdFn := func(fileId string) (targetUrls []string, err error) {
 		return masterClient.LookupFileId(fileId)
 	}
 
-	chunkViews := ViewFromChunks(lookupFileIdFn, chunks, 0, math.MaxInt64)
+	chunkViews := ViewFromChunks(lookupFileIdFn, chunks, 0, int64(len(buffer)))
+
+	idx := 0
 
 	for _, chunkView := range chunkViews {
 		urlStrings, err := lookupFileIdFn(chunkView.FileId)
 		if err != nil {
 			glog.V(1).Infof("operation LookupFileId %s failed, err: %v", chunkView.FileId, err)
-			return nil, err
+			return err
 		}
 
-		data, err := retriedFetchChunkData(urlStrings, chunkView.CipherKey, chunkView.IsGzipped, chunkView.IsFullChunk(), chunkView.Offset, int(chunkView.Size))
+		n, err := retriedFetchChunkData(buffer[idx:idx+int(chunkView.Size)], urlStrings, chunkView.CipherKey, chunkView.IsGzipped, chunkView.IsFullChunk(), chunkView.Offset)
 		if err != nil {
-			return nil, err
+			return err
 		}
-		buffer.Write(data)
+		idx += n
 	}
-	return buffer.Bytes(), nil
+	return nil
 }
 
 // ----------------  ChunkStreamReader ----------------------------------

weed/server/filer_server_handlers_read.go

@@ -4,6 +4,7 @@ import (
 	"bytes"
 	"context"
 	"fmt"
+	"github.com/chrislusf/seaweedfs/weed/util/mem"
 	"io"
 	"mime"
 	"net/http"
@@ -189,7 +190,9 @@ func (fs *FilerServer) GetOrHeadHandler(w http.ResponseWriter, r *http.Request)
 		}
 		width, height, mode, shouldResize := shouldResizeImages(ext, r)
 		if shouldResize {
-			data, err := filer.ReadAll(fs.filer.MasterClient, entry.Chunks)
+			data := mem.Allocate(int(totalSize))
+			defer mem.Free(data)
+			err := filer.ReadAll(data, fs.filer.MasterClient, entry.Chunks)
 			if err != nil {
 				glog.Errorf("failed to read %s: %v", path, err)
 				w.WriteHeader(http.StatusNotModified)

weed/util/chunk_cache/chunk_cache.go

@@ -11,8 +11,6 @@ import (
 var ErrorOutOfBounds = errors.New("attempt to read out of bounds")
 
 type ChunkCache interface {
-	GetChunk(fileId string, minSize uint64) (data []byte)
-	GetChunkSlice(fileId string, offset, length uint64) []byte
 	ReadChunkAt(data []byte, fileId string, offset uint64) (n int, err error)
 	SetChunk(fileId string, data []byte)
 }
@@ -45,107 +43,6 @@ func NewTieredChunkCache(maxEntries int64, dir string, diskSizeInUnit int64, uni
 	return c
 }
 
-func (c *TieredChunkCache) GetChunk(fileId string, minSize uint64) (data []byte) {
-	if c == nil {
-		return
-	}
-
-	c.RLock()
-	defer c.RUnlock()
-
-	return c.doGetChunk(fileId, minSize)
-}
-
-func (c *TieredChunkCache) doGetChunk(fileId string, minSize uint64) (data []byte) {
-
-	if minSize <= c.onDiskCacheSizeLimit0 {
-		data = c.memCache.GetChunk(fileId)
-		if len(data) >= int(minSize) {
-			return data
-		}
-	}
-
-	fid, err := needle.ParseFileIdFromString(fileId)
-	if err != nil {
-		glog.Errorf("failed to parse file id %s", fileId)
-		return nil
-	}
-
-	if minSize <= c.onDiskCacheSizeLimit0 {
-		data = c.diskCaches[0].getChunk(fid.Key)
-		if len(data) >= int(minSize) {
-			return data
-		}
-	}
-	if minSize <= c.onDiskCacheSizeLimit1 {
-		data = c.diskCaches[1].getChunk(fid.Key)
-		if len(data) >= int(minSize) {
-			return data
-		}
-	}
-	{
-		data = c.diskCaches[2].getChunk(fid.Key)
-		if len(data) >= int(minSize) {
-			return data
-		}
-	}
-
-	return nil
-
-}
-
-func (c *TieredChunkCache) GetChunkSlice(fileId string, offset, length uint64) []byte {
-	if c == nil {
-		return nil
-	}
-
-	c.RLock()
-	defer c.RUnlock()
-
-	return c.doGetChunkSlice(fileId, offset, length)
-}
-
-func (c *TieredChunkCache) doGetChunkSlice(fileId string, offset, length uint64) (data []byte) {
-
-	minSize := offset + length
-	if minSize <= c.onDiskCacheSizeLimit0 {
-		data, err := c.memCache.getChunkSlice(fileId, offset, length)
-		if err != nil {
-			glog.Errorf("failed to read from memcache: %s", err)
-		}
-		if len(data) >= int(minSize) {
-			return data
-		}
-	}
-
-	fid, err := needle.ParseFileIdFromString(fileId)
-	if err != nil {
-		glog.Errorf("failed to parse file id %s", fileId)
-		return nil
-	}
-
-	if minSize <= c.onDiskCacheSizeLimit0 {
-		data = c.diskCaches[0].getChunkSlice(fid.Key, offset, length)
-		if len(data) >= int(minSize) {
-			return data
-		}
-	}
-	if minSize <= c.onDiskCacheSizeLimit1 {
-		data = c.diskCaches[1].getChunkSlice(fid.Key, offset, length)
-		if len(data) >= int(minSize) {
-			return data
-		}
-	}
-	{
-		data = c.diskCaches[2].getChunkSlice(fid.Key, offset, length)
-		if len(data) >= int(minSize) {
-			return data
-		}
-	}
-
-	return nil
-}
-
 func (c *TieredChunkCache) ReadChunkAt(data []byte, fileId string, offset uint64) (n int, err error) {
 	if c == nil {
 		return 0, nil