implemented priority preloading

cmd/cachefs/main.go

@@ -46,7 +46,7 @@ func main() {
 	flag.StringVar(&listenHttp, "listen", "127.0.0.1:8080", "listen addr:port")
 	flag.StringVar(&listenWebdav, "webdav", "", "listen addr:port for webdav")
 	flag.StringVar(&listenCache, "cache", "", "listen addr:port for cache only")
-	flag.IntVar(&max, "max", -1, "max parallel preloads")
+	flag.IntVar(&max, "max", 1, "max parallel preloads")
 	flag.IntVar(&bs, "bs", -1, "tune preload buffer size in bytes (default: 8192)")
 	flag.Int64Var(&quota, "quota", 1, "max disk usage quota for the dst cache in GiB")
 	flag.BoolVar(&block, "block", true, "block until sftp is connected")

pkg/fs/file.go

@@ -50,13 +50,14 @@ func (p *preload) Read(data []byte) (n int, err error) {
 func (f *File) Preload(ctx context.Context, unlock func()) {
 	log := f.log
 	defer f.Close()
-	defer unlock()
 	if f.offline {
 		log.V(2).Error(errors.New("no preload in offline mode"), "error preloading file")
+		unlock()
 		return
 	}
 	if f.md.FullyCached() {
 		log.V(2).Info("skipped preload for fully cached file")
+		unlock()
 		return
 	}
 
@@ -65,6 +66,7 @@ func (f *File) Preload(ctx context.Context, unlock func()) {
 	_, err := io.Copy(Discard, p)
 	if err == context.Canceled {
 		log.V(2).Info("preload canceled", "skipped", p.skipped, "written", p.written)
+		// do not call unlock() to keep preload in list
 		return
 	}
 	if err != nil && err != io.EOF {
@@ -75,6 +77,7 @@ func (f *File) Preload(ctx context.Context, unlock func()) {
 		log.Error(err, "error closing cache file")
 	}
 	log.V(2).Info("preload finished", "skipped", p.skipped, "written", p.written)
+	unlock()
 }
 
 func (f *File) Read(p []byte) (n int, err error) {

pkg/fs/fs.go

@@ -145,16 +145,16 @@ func (fs *FS) QuotaUsage() (cur, max int64) {
 	return fs.q.Usage()
 }
 
-func (fs *FS) CancelPreload(name string) {
+func (fs *FS) RemovePreload(name string) {
-	fs.ph.CancelPreload(name)
+	fs.ph.RemovePreload(name)
 }
 
 func (fs *FS) Preloads() Preloads {
 	return fs.ph.Preloads()
 }
 
-func (fs *FS) Preload(name string) {
+func (fs *FS) Preload(name string, prio int) {
-	fs.ph.Preload(name)
+	fs.ph.Preload(name, prio)
 }
 
 func skipLog(name string) bool {

pkg/fs/preload.go

@@ -4,138 +4,160 @@ package fs
 
 import (
 	"context"
-	"errors"
 	"sync"
 
 	"github.com/go-logr/logr"
 	"golang.org/x/exp/slices"
 )
 
+type queue []*Preload
+
+func (queue) LessReverse(i, j *Preload) bool { return i.Prio > j.Prio }
+
+func (q *queue) Head() (p *Preload) {
+	l := len(*q)
+	if l > 0 {
+		p = (*q)[l-1]
+	}
+	return
+}
+
+func (q *queue) Pop() (p *Preload) {
+	l := len(*q)
+	if l > 0 {
+		p = q.Head()
+		*q = (*q)[:l-1]
+	}
+	return
+}
+
+func (q *queue) Sort() {
+	slices.SortFunc(*q, q.LessReverse)
+}
+
+func (q *queue) Add(ph *PreloadHandler, name string, prio int) {
+	for _, p := range *q {
+		if p.Name == name {
+			p.Prio += prio
+			q.Sort()
+			return
+		}
+	}
+	q.Append(&Preload{Name: name, ph: ph})
+}
+
+func (q *queue) Append(p *Preload) {
+	*q = append(*q, p)
+	q.Sort()
+}
+
+func (q *queue) Remove(name string) {
+	for i, p := range *q {
+		if p.Name == name {
+			p.stop()
+			*q = slices.Delete(*q, i, i+1)
+			q.Sort()
+			return
+		}
+	}
+}
+
 type Preload struct {
+	ph      *PreloadHandler
 	Name    string
 	cancel  func()
+	Prio    int
 	Status  int
 	Running bool
 }
 
-type Preloads []*Preload
+type Preloads []Preload
-
-func (Preloads) Less(i, j *Preload) bool { return i.Name < j.Name }
 
 type PreloadHandler struct {
 	mu  sync.RWMutex
 	log logr.Logger
 	fs  *FS
-	pm    map[string]*Preload
+	q   queue
-	sched chan *Preload
 	fin chan string
-	pre   int
 	max int
 }
 
 func NewPreloadHandler(ctx context.Context, fs *FS, max int, log logr.Logger) (ph *PreloadHandler) {
-	if max < -1 {
+	if max <= 0 {
-		max = -1
+		max = 1
 	}
 	ph = &PreloadHandler{
 		log: log,
 		fs:  fs,
-		pm:    make(map[string]*Preload),
+		q:   make(queue, 0),
-		sched: make(chan *Preload, 1),
 		fin: make(chan string, 1),
 		max: max,
 	}
-	go ph.preload(ctx)
 	go ph.preloadFinish(ctx)
 	return
 }
 
-func (ph *PreloadHandler) CancelPreload(name string) {
+func (ph *PreloadHandler) RemovePreload(name string) {
-	ph.mu.Lock()
+	ph.mu.RLock()
-	defer ph.mu.Unlock()
+	defer ph.mu.RUnlock()
-	p, ok := ph.pm[name]
+	ph.q.Remove(name)
-	if ok {
+	ph.schedule()
-		if p.Running {
-			p.cancel()
-		}
-		delete(ph.pm, name)
-	}
 }
 
 func (ph *PreloadHandler) Preloads() (ps Preloads) {
 	ph.mu.RLock()
 	defer ph.mu.RUnlock()
-	for _, p := range ph.pm {
+	ps = make(Preloads, len(ph.q))
-		ps = append(ps, &Preload{
+	for i, v := range ph.q {
-			Name:    p.Name,
+		ps[i] = *v
-			Running: p.Running,
+		ps[i].Status = ph.fs.CacheStatus(v.Name)
-			Status:  ph.fs.CacheStatus(p.Name),
-		})
 	}
-	slices.SortFunc(ps, ps.Less)
 	return
 }
 
-func (ph *PreloadHandler) Preload(name string) {
+func (ph *PreloadHandler) Preload(name string, prio int) {
 	ph.mu.Lock()
 	defer ph.mu.Unlock()
-
+	ph.q.Add(ph, name, prio)
-	p, ok := ph.pm[name]
+	ph.schedule()
-	if !ok {
-		p = &Preload{Name: name}
-		ph.pm[name] = p
-		if ph.max == -1 || ph.pre < ph.max {
-			ph.sched <- p
-		}
-		return
-	}
-
-	if p.Running {
-		ph.log.WithValues("file", name).Error(errors.New("preload is running"), "error starting preload")
-	}
-	return
 }
 
-func (ph *PreloadHandler) nextPreload() {
+func (ph *PreloadHandler) schedule() {
-	if ph.pre == ph.max {
+	for i := 0; i < len(ph.q); i++ {
-		return
+		if i < ph.max {
+			ph.q[i].start()
+		} else {
+			ph.q[i].stop()
 		}
-	for _, p := range ph.pm {
-		if p.Running {
-			continue
-		}
-		ph.sched <- p
-		return
 	}
 }
 
-func (ph *PreloadHandler) preload(ctx context.Context) {
+func (p *Preload) start() {
-	var p *Preload
+	if p.Running {
-	for {
-		select {
-		case <-ctx.Done():
 		return
-		case p = <-ph.sched:
 	}
 	name := p.Name
-		file, err := ph.fs.Open(name)
+	file, err := p.ph.fs.Open(name)
 	if err != nil {
-			ph.log.Error(err, "error staring next preload", "file", name)
+		p.ph.log.Error(err, "error staring next preload", "file", name)
 		return
 	}
 	f, ok := file.(*File)
 	if !ok {
-			continue
+		return
 	}
 	ctx, cancel := context.WithCancel(context.Background())
-		ph.mu.Lock()
-		ph.pre++
 	p.Running = true
 	p.cancel = cancel
-		ph.mu.Unlock()
 	go f.Preload(ctx, func() {
-			ph.fin <- name
+		p.ph.fin <- name
 	})
+}
+
+func (p *Preload) stop() {
+	if p.Running {
+		p.cancel()
+		p.Running = false
 	}
 }
 
@@ -147,23 +169,19 @@ func (ph *PreloadHandler) preloadFinish(ctx context.Context) {
 			return
 		case name := <-ph.fin:
 			ph.mu.Lock()
-			delete(ph.pm, name)
+			ph.q.Remove(name)
-			ph.pre--
+			ph.schedule()
-			ph.nextPreload()
 			ph.mu.Unlock()
 		}
 	}
 }
 
 func (ph *PreloadHandler) close() {
-	for _, p := range ph.pm {
+	for _, p := range ph.q {
-		if p.Running {
+		p.stop()
-			p.cancel()
-		}
 	}
 	for {
 		select {
-		case <-ph.sched:
 		case <-ph.fin:
 		default:
 			return

pkg/srv/interceptor.go

@@ -60,6 +60,7 @@ type file struct {
 	URI     template.HTML
 	Anchor  string
 	Status  int
+	Prio    int
 	Running bool
 }
 
@@ -136,12 +137,10 @@ func getPreloads(path string, fs *fs.FS) (dc dirContents) {
 			Name:    template.HTML(p.Name),
 			URI:     template.HTML(p.Name),
 			Status:  p.Status,
+			Prio:    p.Prio,
 			Running: p.Running,
 		})
 	}
-	slices.SortFunc(dc.Files, func(i, _ file) bool {
-		return i.Running
-	})
 	return
 }
 

pkg/srv/srv.go

@@ -85,11 +85,16 @@ func (fs *FileServer) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	}
 
 	if !d.IsDir() {
-		if option == "p" || option == "s" {
+		if option == "p" || option == "i" || option == "d" || option == "s" {
-			if option == "p" {
+			switch option {
-				fs.fs.Preload(p)
+			case "p":
-			} else if option == "s" {
+				fs.fs.Preload(p, 0)
-				fs.fs.CancelPreload(p)
+			case "i":
+				fs.fs.Preload(p, 1)
+			case "d":
+				fs.fs.Preload(p, -1)
+			case "s":
+				fs.fs.RemovePreload(p)
 			}
 			rdir := "/"
 			if r.FormValue("r") == "preloads" {

pkg/srv/templates/preloads.html

@@ -1,5 +1,7 @@
 {{define "body" -}}
 <pre>[v]: show video
+[+]: increase priority
+[-]: decrease priority
 [s]: stop preloading
 Quota: {{.QuotaCur}} / {{.QuotaMax}} GiB
 </pre>
@@ -12,7 +14,7 @@ Quota: {{.QuotaCur}} / {{.QuotaMax}} GiB
   <tr class="listitem">
     <td class="listpath"><a href="{{$s.URI}}">{{$s.Name}}</a></td>
     <td class="listoptions">
-      {{if ge $s.Status 0}}<span>{{$s.Status}}%</span>{{end}}<span class="status-{{if $s.Running}}green">[running{{else}}yellow">[queued{{end}}]</span><a href="{{$s.URI}}?o=v">[v]</a><a href="{{$s.Name}}?o=s&r=preloads">[s]</a>
+      {{if ge $s.Status 0}}<span>{{$s.Status}}%</span>{{end}}<span class="status-{{if $s.Running}}green">[running{{else}}yellow">[queued{{end}}]</span><span>{{$s.Prio}}</span><a href="{{$s.URI}}?o=v">[v]</a><a href="{{$s.Name}}?o=s&r=preloads">[s]</a><a href="{{$s.Name}}?o=i&r=preloads">[+]</a><a href="{{$s.Name}}?o=d&r=preloads">[-]</a>
     </td>
   </tr>
   <tr class="spacer"><td colspan="2">