mount: avoid duplicated reads

weed/filer/reader_at.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"fmt"
 	"io"
+	"math/rand"
 	"sync"
 
 	"github.com/chrislusf/seaweedfs/weed/glog"
@@ -17,9 +18,12 @@ type ChunkReadAt struct {
 	chunkViews   []*ChunkView
 	lookupFileId func(fileId string) (targetUrl string, err error)
 	readerLock   sync.Mutex
+	fetcherLock  sync.Mutex
 	fileSize     int64
 
-	chunkCache chunk_cache.ChunkCache
+	lastChunkFileId string
+	lastChunkData   []byte
+	chunkCache      chunk_cache.ChunkCache
 }
 
 // var _ = io.ReaderAt(&ChunkReadAt{})
@@ -27,28 +31,36 @@ type ChunkReadAt struct {
 type LookupFileIdFunctionType func(fileId string) (targetUrl string, err error)
 
 func LookupFn(filerClient filer_pb.FilerClient) LookupFileIdFunctionType {
+
+	vidCache := make(map[string]*filer_pb.Locations)
 	return func(fileId string) (targetUrl string, err error) {
-		err = filerClient.WithFilerClient(func(client filer_pb.SeaweedFilerClient) error {
-			vid := VolumeId(fileId)
-			resp, err := client.LookupVolume(context.Background(), &filer_pb.LookupVolumeRequest{
-				VolumeIds: []string{vid},
+		vid := VolumeId(fileId)
+		locations, found := vidCache[vid]
+
+		if !found {
+			// println("looking up volume", vid)
+			err = filerClient.WithFilerClient(func(client filer_pb.SeaweedFilerClient) error {
+				resp, err := client.LookupVolume(context.Background(), &filer_pb.LookupVolumeRequest{
+					VolumeIds: []string{vid},
+				})
+				if err != nil {
+					return err
+				}
+
+				locations = resp.LocationsMap[vid]
+				if locations == nil || len(locations.Locations) == 0 {
+					glog.V(0).Infof("failed to locate %s", fileId)
+					return fmt.Errorf("failed to locate %s", fileId)
+				}
+				vidCache[vid] = locations
+
+				return nil
 			})
-			if err != nil {
-				return err
-			}
-
-			locations := resp.LocationsMap[vid]
-			if locations == nil || len(locations.Locations) == 0 {
-				glog.V(0).Infof("failed to locate %s", fileId)
-				return fmt.Errorf("failed to locate %s", fileId)
-			}
-
-			volumeServerAddress := filerClient.AdjustedUrl(locations.Locations[0].Url)
+		}
 
-			targetUrl = fmt.Sprintf("http://%s/%s", volumeServerAddress, fileId)
+		volumeServerAddress := filerClient.AdjustedUrl(locations.Locations[rand.Intn(len(locations.Locations))].Url)
+		targetUrl = fmt.Sprintf("http://%s/%s", volumeServerAddress, fileId)
 
-			return nil
-		})
 		return
 	}
 }
@@ -125,25 +137,34 @@ func (c *ChunkReadAt) doReadAt(p []byte, offset int64) (n int, err error) {
 
 func (c *ChunkReadAt) readFromWholeChunkData(chunkView *ChunkView) (chunkData []byte, err error) {
 
+	c.fetcherLock.Lock()
+	defer c.fetcherLock.Unlock()
+
+	if c.lastChunkFileId == chunkView.FileId {
+		return c.lastChunkData, nil
+	}
+
 	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)
 
 	chunkData = c.chunkCache.GetChunk(chunkView.FileId, chunkView.ChunkSize)
 	if chunkData != nil {
 		glog.V(4).Infof("cache hit %s [%d,%d)", chunkView.FileId, chunkView.LogicOffset-chunkView.Offset, chunkView.LogicOffset-chunkView.Offset+int64(len(chunkData)))
 	} else {
-		glog.V(4).Infof("doFetchFullChunkData %s", chunkView.FileId)
-		chunkData, err = c.doFetchFullChunkData(chunkView.FileId, chunkView.CipherKey, chunkView.IsGzipped)
+		chunkData, err = c.doFetchFullChunkData(chunkView)
 		if err != nil {
 			return
 		}
 		c.chunkCache.SetChunk(chunkView.FileId, chunkData)
+		c.lastChunkData = chunkData
+		c.lastChunkFileId = chunkView.FileId
 	}
 
 	return
 }
 
-func (c *ChunkReadAt) doFetchFullChunkData(fileId string, cipherKey []byte, isGzipped bool) ([]byte, error) {
+func (c *ChunkReadAt) doFetchFullChunkData(chunkView *ChunkView) ([]byte, error) {
+	data, err := fetchChunk(c.lookupFileId, chunkView.FileId, chunkView.CipherKey, chunkView.IsGzipped)
 
-	return fetchChunk(c.lookupFileId, fileId, cipherKey, isGzipped)
+	return data, err
 
 }