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package filer
import (
"fmt"
"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.Mutex
cond *sync.Cond
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(chunkViews []*ChunkView) {
if rc.lookupFileIdFn == nil {
return
}
rc.Lock()
defer rc.Unlock()
for _, chunkView := range chunkViews {
if _, found := rc.downloaders[chunkView.FileId]; found {
continue
}
if len(rc.downloaders) >= rc.limit {
// if still no slots, return
return
}
// glog.V(4).Infof("prefetch %s offset %d", chunkView.FileId, chunkView.LogicOffset)
// cache this chunk if not yet
cacher := newSingleChunkCacher(rc, chunkView.FileId, chunkView.CipherKey, chunkView.IsGzipped, int(chunkView.ChunkSize), false)
cacher.wg.Add(1)
go cacher.startCaching()
cacher.wg.Wait()
rc.downloaders[chunkView.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 {
if n, err := cacher.readChunkAt(buffer, offset); n != 0 && err == nil {
return n, err
}
}
if shouldCache || rc.lookupFileIdFn == nil {
n, err := rc.chunkCache.ReadChunkAt(buffer, fileId, uint64(offset))
if n > 0 {
return n, err
}
}
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()
}
}
// glog.V(4).Infof("cache1 %s", fileId)
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) UnCache(fileId string) {
rc.Lock()
defer rc.Unlock()
// glog.V(4).Infof("uncache %s", fileId)
if downloader, found := rc.downloaders[fileId]; found {
downloader.destroy()
delete(rc.downloaders, fileId)
}
}
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,
}
t.cond = sync.NewCond(t)
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)
}
s.cond.Broadcast()
return
}
func (s *SingleChunkCacher) destroy() {
s.Lock()
defer s.Unlock()
if s.data != nil {
mem.Free(s.data)
s.data = nil
}
}
func (s *SingleChunkCacher) readChunkAt(buf []byte, offset int64) (int, error) {
s.Lock()
defer s.Unlock()
for s.completedTime.IsZero() {
s.cond.Wait()
}
if s.err != nil {
return 0, s.err
}
if len(s.data) == 0 {
return 0, nil
}
return copy(buf, s.data[offset:]), nil
}
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