From 675bc4d1252a9be91aa611d68a62c7049f9d344a Mon Sep 17 00:00:00 2001
From: ston1th <ston1th@giftfish.de>
Date: Sun, 20 Mar 2022 10:19:03 +0100
Subject: [PATCH] added stat cache

---
 pkg/fs/fs.go   | 61 +++++++++++++++++++++++++++--------------------
 pkg/fs/stat.go | 64 ++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 100 insertions(+), 25 deletions(-)
 create mode 100644 pkg/fs/stat.go

diff --git a/pkg/fs/fs.go b/pkg/fs/fs.go
index e9d832d..f8092db 100644
--- a/pkg/fs/fs.go
+++ b/pkg/fs/fs.go
@@ -22,18 +22,20 @@ import (
 )
 
 type FS struct {
-	mu      sync.RWMutex
-	log     logr.Logger
-	NoCache http.Handler
-	src     string
-	dst     string
-	mdf     *os.File
-	jenc    *json.Encoder
-	dc      *DirCache
-	q       *Quota
-	md      MetadataMap
-	pm      map[string]func()
-	cancel  func()
+	mu          sync.RWMutex
+	log         logr.Logger
+	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()
 }
 
 func NewFS(max int64, src, dst, metadata string, log logr.Logger) (fs *FS, err error) {
@@ -53,16 +55,21 @@ 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,
-		dc:      NewDirCache(),
-		md:      make(MetadataMap),
-		pm:      make(map[string]func()),
-		jenc:    json.NewEncoder(mdf),
+		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),
 	}
 	fs.q, err = NewQuota(max, fs, fs.log.WithName("quota"))
 	if err != nil {
@@ -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())
-	fs.cancel = cancel
-	go fs.flusher(ctx)
+	go fs.flusher(flushCtx)
 	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()
 	}
diff --git a/pkg/fs/stat.go b/pkg/fs/stat.go
new file mode 100644
index 0000000..841870f
--- /dev/null
+++ b/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}
+}