Show scan rate in web GUI

lib/scanner/walk.go

@@ -16,6 +16,7 @@ import (
 	"time"
 	"unicode/utf8"
 
+	"github.com/rcrowley/go-metrics"
 	"github.com/syncthing/syncthing/lib/db"
 	"github.com/syncthing/syncthing/lib/events"
 	"github.com/syncthing/syncthing/lib/osutil"
@@ -143,7 +144,11 @@ func (w *Walker) Walk() (chan protocol.FileInfo, error) {
 	// which it receives the files we ask it to hash.
 	go func() {
 		var filesToHash []protocol.FileInfo
-		var total, progress int64 = 1, 0
+		var total int64 = 1
+
+		progress := newByteCounter()
+		defer progress.Close()
+
 		for file := range toHashChan {
 			filesToHash = append(filesToHash, file)
 			total += int64(file.CachedSize)
@@ -151,7 +156,7 @@ func (w *Walker) Walk() (chan protocol.FileInfo, error) {
 
 		realToHashChan := make(chan protocol.FileInfo)
 		done := make(chan struct{})
-		newParallelHasher(w.Dir, w.BlockSize, w.Hashers, finishedChan, realToHashChan, &progress, done, w.Cancel)
+		newParallelHasher(w.Dir, w.BlockSize, w.Hashers, finishedChan, realToHashChan, progress, done, w.Cancel)
 
 		// A routine which actually emits the FolderScanProgress events
 		// every w.ProgressTicker ticks, until the hasher routines terminate.
@@ -163,12 +168,14 @@ func (w *Walker) Walk() (chan protocol.FileInfo, error) {
 					ticker.Stop()
 					return
 				case <-ticker.C:
-					current := atomic.LoadInt64(&progress)
-					l.Debugf("Walk %s %s current progress %d/%d (%d%%)", w.Dir, w.Subs, current, total, current*100/total)
+					current := progress.Total()
+					rate := progress.Rate()
+					l.Debugf("Walk %s %s current progress %d/%d at %.01f MB/s (%d%%)", w.Dir, w.Subs, current, total, rate/1024/1024, current*100/total)
 					events.Default.Log(events.FolderScanProgress, map[string]interface{}{
 						"folder":  w.Folder,
 						"current": current,
 						"total":   total,
+						"rate":    rate, // bytes per second
 					})
 				case <-w.Cancel:
 					ticker.Stop()
@@ -492,3 +499,48 @@ func SymlinkFlags(t symlinks.TargetType) uint32 {
 	}
 	panic("unknown symlink TargetType")
 }
+
+// A byteCounter gets bytes added to it via Update() and then provides the
+// Total() and one minute moving average Rate() in bytes per second.
+type byteCounter struct {
+	total int64
+	metrics.EWMA
+	stop chan struct{}
+}
+
+func newByteCounter() *byteCounter {
+	c := &byteCounter{
+		EWMA: metrics.NewEWMA1(), // a one minute exponentially weighted moving average
+		stop: make(chan struct{}),
+	}
+	go c.ticker()
+	return c
+}
+
+func (c *byteCounter) ticker() {
+	// The metrics.EWMA expects clock ticks every five seconds in order to
+	// decay the average properly.
+	t := time.NewTicker(5 * time.Second)
+	for {
+		select {
+		case <-t.C:
+			c.Tick()
+		case <-c.stop:
+			t.Stop()
+			return
+		}
+	}
+}
+
+func (c *byteCounter) Update(bytes int64) {
+	atomic.AddInt64(&c.total, bytes)
+	c.EWMA.Update(bytes)
+}
+
+func (c *byteCounter) Total() int64 {
+	return atomic.LoadInt64(&c.total)
+}
+
+func (c *byteCounter) Close() {
+	close(c.stop)
+}