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package filer
import ( "fmt" "github.com/seaweedfs/seaweedfs/weed/util/chunk_cache" "github.com/seaweedfs/seaweedfs/weed/util/mem" "github.com/seaweedfs/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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