added stat cache

pkg/fs/fs.go

@@ -27,13 +27,15 @@ type FS struct {
 	NoCache     http.Handler
 	src         string
 	dst         string
+	statCancel  func()
+	flushCancel func()
 	mdf         *os.File
 	jenc        *json.Encoder
 	dc          *DirCache
+	sc          *StatCache
 	q           *Quota
 	md          MetadataMap
 	pm          map[string]func()
-	cancel  func()
 }
 
 func NewFS(max int64, src, dst, metadata string, log logr.Logger) (fs *FS, err error) {
@@ -53,13 +55,18 @@ func NewFS(max int64, src, dst, metadata string, log logr.Logger) (fs *FS, err e
 	if err != nil {
 		return
 	}
+	statCtx, statCancel := context.WithCancel(context.Background())
+	flushCtx, flushCancel := context.WithCancel(context.Background())
 	fs = &FS{
 		log:         log,
 		NoCache:     http.FileServer(http.Dir(src)),
 		src:         src,
 		dst:         dst,
 		mdf:         mdf,
+		statCancel:  statCancel,
+		flushCancel: flushCancel,
 		dc:          NewDirCache(),
+		sc:          NewStatCache(statCtx),
 		md:          make(MetadataMap),
 		pm:          make(map[string]func()),
 		jenc:        json.NewEncoder(mdf),
@@ -74,9 +81,7 @@ func NewFS(max int64, src, dst, metadata string, log logr.Logger) (fs *FS, err e
 	}
 	fs.initMetadata()
 	fs.q.Init()
-	ctx, cancel := context.WithCancel(context.Background())
+	go fs.flusher(flushCtx)
-	fs.cancel = cancel
-	go fs.flusher(ctx)
 	return fs, err
 }
 
@@ -110,8 +115,13 @@ func (fs *FS) Stat(name string) (fi stdfs.FileInfo, err error) {
 
 func (fs *FS) StatWithOffline(name string) (fi stdfs.FileInfo, offline bool, err error) {
 	sp, dp := fs.paths(name)
+	fi, err = fs.sc.Get(name)
+	if err == nil {
+		return
+	}
 	fi, err = os.Stat(sp)
 	if err == nil {
+		fs.sc.Set(name, fi)
 		return
 	}
 	fi, err = os.Stat(dp)
@@ -347,7 +357,8 @@ func (fs *FS) flushMetadata() {
 }
 
 func (fs *FS) Close() {
-	fs.cancel()
+	fs.flushCancel()
+	fs.statCancel()
 	for _, cancel := range fs.pm {
 		cancel()
 	}

pkg/fs/stat.go

@@ -0,0 +1,64 @@
+// Copyright (C) 2022 Marius Schellenberger
+
+package fs
+
+import (
+	"context"
+	"os"
+	"sync"
+	"time"
+)
+
+const statExpiry = time.Minute * 5
+
+type statCacheEntry struct {
+	mtime time.Time
+	fi    os.FileInfo
+}
+
+type StatCache struct {
+	mu  sync.RWMutex
+	ctx context.Context
+	m   map[string]*statCacheEntry
+}
+
+func NewStatCache(ctx context.Context) *StatCache {
+	sc := &StatCache{ctx: ctx, m: make(map[string]*statCacheEntry)}
+	go sc.cleanup()
+	return sc
+}
+
+func (sc *StatCache) cleanup() {
+	t := time.NewTicker(statExpiry)
+	defer t.Stop()
+	for {
+		select {
+		case <-sc.ctx.Done():
+			return
+		case <-t.C:
+		}
+		sc.mu.Lock()
+		now := time.Now()
+		for k, sce := range sc.m {
+			if now.After(sce.mtime) {
+				delete(sc.m, k)
+			}
+		}
+		sc.mu.Unlock()
+	}
+}
+
+func (sc *StatCache) Get(name string) (os.FileInfo, error) {
+	sc.mu.RLock()
+	defer sc.mu.RUnlock()
+	if sce, ok := sc.m[name]; ok {
+		return sce.fi, nil
+	}
+	return nil, NoCacheEntry
+}
+
+func (sc *StatCache) Set(name string, fi os.FileInfo) {
+	sc.mu.Lock()
+	defer sc.mu.Unlock()
+	sc.m[name] = &statCacheEntry{time.Now().Add(statExpiry), fi}
+}