fs: cache recent dir for a bit

Change-Id: Id85344038d38dedc134435463d96d8b836edbcd7

pkg/fs/recent.go

@@ -39,9 +39,11 @@ type recentDir struct {
 	noXattr
 	fs *CamliFileSystem
 
-	mu      sync.Mutex
+	mu          sync.Mutex
-	ents    map[string]*search.DescribedBlob // filename to blob meta
+	ents        map[string]*search.DescribedBlob // filename to blob meta
-	modTime map[string]time.Time             // filename to permanode modtime
+	modTime     map[string]time.Time             // filename to permanode modtime
+	lastReaddir time.Time
+	lastNames   []string
 }
 
 func (n *recentDir) Attr() fuse.Attr {
@@ -52,10 +54,22 @@ func (n *recentDir) Attr() fuse.Attr {
 	}
 }
 
+const recentSearchInterval = 10 * time.Second
+
 func (n *recentDir) ReadDir(intr fs.Intr) ([]fuse.Dirent, fuse.Error) {
-	log.Printf("fs.recent: ReadDir / searching")
+	var ents []fuse.Dirent
+
 	n.mu.Lock()
 	defer n.mu.Unlock()
+	if n.lastReaddir.After(time.Now().Add(-recentSearchInterval)) {
+		log.Printf("fs.recent: ReadDir from cache")
+		for _, name := range n.lastNames {
+			ents = append(ents, fuse.Dirent{Name: name})
+		}
+		return ents, nil
+	}
+
+	log.Printf("fs.recent: ReadDir, doing search")
 
 	n.ents = make(map[string]*search.DescribedBlob)
 	n.modTime = make(map[string]time.Time)
@@ -67,7 +81,7 @@ func (n *recentDir) ReadDir(intr fs.Intr) ([]fuse.Dirent, fuse.Error) {
 		return nil, fuse.EIO
 	}
 
-	var ents []fuse.Dirent
+	n.lastNames = nil
 	for _, ri := range res.Recent {
 		modTime := ri.ModTime.Time()
 		meta := res.Meta.Get(ri.BlobRef)
@@ -103,11 +117,13 @@ func (n *recentDir) ReadDir(intr fs.Intr) ([]fuse.Dirent, fuse.Error) {
 		n.ents[name] = ccMeta
 		n.modTime[name] = modTime
 		log.Printf("fs.recent: name %q = %v (at %v -> %v)", name, ccMeta.BlobRef, ri.ModTime.Time(), modTime)
+		n.lastNames = append(n.lastNames, name)
 		ents = append(ents, fuse.Dirent{
 			Name: name,
 		})
 	}
 	log.Printf("fs.recent returning %d entries", len(ents))
+	n.lastReaddir = time.Now()
 	return ents, nil
 }