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reader_at.go
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reader_at.go
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package filer
import (
"context"
"fmt"
"github.com/chrislusf/seaweedfs/weed/glog"
"github.com/chrislusf/seaweedfs/weed/pb/filer_pb"
"github.com/chrislusf/seaweedfs/weed/util/chunk_cache"
"github.com/chrislusf/seaweedfs/weed/wdclient"
"github.com/golang/groupcache/singleflight"
"io"
"math/rand"
"sync"
"time"
)
var (
ReadWaitTime = 6 * time.Second
)
type ChunkReadAt struct {
masterClient *wdclient.MasterClient
chunkViews []*ChunkView
lookupFileId LookupFileIdFunctionType
readerLock sync.Mutex
fileSize int64
fetchGroup singleflight.Group
lastChunkFileId string
lastChunkData []byte
chunkCache chunk_cache.ChunkCache
}
// var _ = io.ReaderAt(&ChunkReadAt{})
type LookupFileIdFunctionType func(fileId string) (targetUrls []string, err error)
func LookupFn(filerClient filer_pb.FilerClient) LookupFileIdFunctionType {
vidCache := make(map[string]*filer_pb.Locations)
return func(fileId string) (targetUrls []string, err error) {
vid := VolumeId(fileId)
locations, found := vidCache[vid]
waitTime := time.Second
for !found && waitTime < ReadWaitTime {
// 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 {
break
}
glog.V(1).Infof("wait for volume %s", vid)
time.Sleep(waitTime)
waitTime += waitTime / 2
}
if err != nil {
return nil, err
}
for _, loc := range locations.Locations {
volumeServerAddress := filerClient.AdjustedUrl(loc)
targetUrl := fmt.Sprintf("http://%s/%s", volumeServerAddress, fileId)
targetUrls = append(targetUrls, targetUrl)
}
for i := len(targetUrls) - 1; i > 0; i-- {
j := rand.Intn(i + 1)
targetUrls[i], targetUrls[j] = targetUrls[j], targetUrls[i]
}
return
}
}
func NewChunkReaderAtFromClient(filerClient filer_pb.FilerClient, chunkViews []*ChunkView, chunkCache chunk_cache.ChunkCache, fileSize int64) *ChunkReadAt {
return &ChunkReadAt{
chunkViews: chunkViews,
lookupFileId: LookupFn(filerClient),
chunkCache: chunkCache,
fileSize: fileSize,
}
}
func (c *ChunkReadAt) ReadAt(p []byte, offset int64) (n int, err error) {
c.readerLock.Lock()
defer c.readerLock.Unlock()
glog.V(4).Infof("ReadAt [%d,%d) of total file size %d bytes %d chunk views", offset, offset+int64(len(p)), c.fileSize, len(c.chunkViews))
return c.doReadAt(p[n:], offset+int64(n))
}
func (c *ChunkReadAt) doReadAt(p []byte, offset int64) (n int, err error) {
var buffer []byte
startOffset, remaining := offset, int64(len(p))
var nextChunk *ChunkView
for i, chunk := range c.chunkViews {
if remaining <= 0 {
break
}
if i+1 < len(c.chunkViews) {
nextChunk = c.chunkViews[i+1]
} else {
nextChunk = nil
}
if startOffset < chunk.LogicOffset {
gap := int(chunk.LogicOffset - startOffset)
glog.V(4).Infof("zero [%d,%d)", startOffset, startOffset+int64(gap))
n += int(min(int64(gap), remaining))
startOffset, remaining = chunk.LogicOffset, remaining-int64(gap)
if remaining <= 0 {
break
}
}
// fmt.Printf(">>> doReadAt [%d,%d), chunk[%d,%d)\n", offset, offset+int64(len(p)), chunk.LogicOffset, chunk.LogicOffset+int64(chunk.Size))
chunkStart, chunkStop := max(chunk.LogicOffset, startOffset), min(chunk.LogicOffset+int64(chunk.Size), startOffset+remaining)
if chunkStart >= chunkStop {
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))
buffer, err = c.readFromWholeChunkData(chunk, nextChunk)
if err != nil {
glog.Errorf("fetching chunk %+v: %v\n", chunk, err)
return
}
bufferOffset := chunkStart - chunk.LogicOffset + chunk.Offset
copied := copy(p[startOffset-offset:chunkStop-chunkStart+startOffset-offset], buffer[bufferOffset:bufferOffset+chunkStop-chunkStart])
n += copied
startOffset, remaining = startOffset+int64(copied), remaining-int64(copied)
}
glog.V(4).Infof("doReadAt [%d,%d), n:%v, err:%v", offset, offset+int64(len(p)), n, err)
if err == nil && remaining > 0 && c.fileSize > startOffset {
delta := int(min(remaining, c.fileSize-startOffset))
glog.V(4).Infof("zero2 [%d,%d) of file size %d bytes", startOffset, startOffset+int64(delta), c.fileSize)
n += delta
}
if err == nil && offset+int64(len(p)) >= c.fileSize {
err = io.EOF
}
// fmt.Printf("~~~ filled %d, err: %v\n\n", n, err)
return
}
func (c *ChunkReadAt) readFromWholeChunkData(chunkView *ChunkView, nextChunkViews ...*ChunkView) (chunkData []byte, err error) {
if c.lastChunkFileId == chunkView.FileId {
return c.lastChunkData, nil
}
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)
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
}
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
}