cmd/tailscale: improve taildrop progress printer on Linux (#9878)

The progress printer was buggy where it would not print correctly
and some of the truncation logic was faulty.

The progress printer now prints something like:

	go1.21.3.linux-amd64.tar.gz               21.53MiB      13.83MiB/s     33.88%    ETA 00:00:03

where it shows
* the number of bytes transferred so far
* the rate of bytes transferred
  (using a 1-second half-life for an exponentially weighted average)
* the progress made as a percentage
* the estimated time
  (as calculated from the rate of bytes transferred)

Other changes:
* It now correctly prints the progress for very small files
* It prints at a faster rate (4Hz instead of 1Hz)
* It uses IEC units for byte quantities
  (to avoid ambiguities of "kb" being kilobits or kilobytes)

Updates tailscale/corp#14772

Signed-off-by: Joe Tsai <joetsai@digital-static.net>

cmd/tailscale/cli/file.go

@@ -18,7 +18,6 @@
 	"path"
 	"path/filepath"
 	"strings"
-	"sync"
 	"sync/atomic"
 	"time"
 	"unicode/utf8"
@@ -29,8 +28,11 @@
 	"tailscale.com/client/tailscale/apitype"
 	"tailscale.com/envknob"
 	"tailscale.com/net/tsaddr"
+	"tailscale.com/syncs"
 	"tailscale.com/tailcfg"
+	tsrate "tailscale.com/tstime/rate"
 	"tailscale.com/util/quarantine"
+	"tailscale.com/util/truncate"
 	"tailscale.com/version"
 )
 
@@ -52,12 +54,12 @@
 
 type countingReader struct {
 	io.Reader
-	n atomic.Uint64
+	n atomic.Int64
 }
 
 func (c *countingReader) Read(buf []byte) (int, error) {
 	n, err := c.Reader.Read(buf)
-	c.n.Add(uint64(n))
+	c.n.Add(int64(n))
 	return n, err
 }
 
@@ -170,75 +172,100 @@ func runCp(ctx context.Context, args []string) error {
 			log.Printf("sending %q to %v/%v/%v ...", name, target, ip, stableID)
 		}
 
-		var (
-			done = make(chan struct{}, 1)
-			wg   sync.WaitGroup
-		)
+		var group syncs.WaitGroup
+		ctxProgress, cancelProgress := context.WithCancel(ctx)
+		defer cancelProgress()
 		if isatty.IsTerminal(os.Stderr.Fd()) {
-			go printProgress(&wg, done, fileContents, name, contentLength)
-			wg.Add(1)
+			group.Go(func() { progressPrinter(ctxProgress, name, fileContents.n.Load, contentLength) })
 		}
 
 		err := localClient.PushFile(ctx, stableID, contentLength, name, fileContents)
+		cancelProgress()
+		group.Wait() // wait for progress printer to stop before reporting the error
 		if err != nil {
 			return err
 		}
 		if cpArgs.verbose {
 			log.Printf("sent %q", name)
 		}
-		done <- struct{}{}
-		wg.Wait()
 	}
 	return nil
 }
 
-const vtRestartLine = "\r\x1b[K"
+func progressPrinter(ctx context.Context, name string, contentCount func() int64, contentLength int64) {
+	var rateValueFast, rateValueSlow tsrate.Value
+	rateValueFast.HalfLife = 1 * time.Second  // fast response for rate measurement
+	rateValueSlow.HalfLife = 10 * time.Second // slow response for ETA measurement
+	var prevContentCount int64
+	print := func() {
+		currContentCount := contentCount()
+		rateValueFast.Add(float64(currContentCount - prevContentCount))
+		rateValueSlow.Add(float64(currContentCount - prevContentCount))
+		prevContentCount = currContentCount
 
-func printProgress(wg *sync.WaitGroup, done <-chan struct{}, r *countingReader, name string, contentLength int64) {
-	defer wg.Done()
-	var lastBytesRead uint64
+		const vtRestartLine = "\r\x1b[K"
+		fmt.Fprintf(os.Stderr, "%s%s    %s    %s",
+			vtRestartLine,
+			rightPad(name, 36),
+			leftPad(formatIEC(float64(currContentCount), "B"), len("1023.00MiB")),
+			leftPad(formatIEC(rateValueFast.Rate(), "B/s"), len("1023.00MiB/s")))
+		if contentLength >= 0 {
+			currContentCount = min(currContentCount, contentLength) // cap at 100%
+			ratioRemain := float64(currContentCount) / float64(contentLength)
+			bytesRemain := float64(contentLength - currContentCount)
+			secsRemain := bytesRemain / rateValueSlow.Rate()
+			secs := int(min(max(0, secsRemain), 99*60*60+59+60+59))
+			fmt.Fprintf(os.Stderr, "    %s    %s",
+				leftPad(fmt.Sprintf("%0.2f%%", 100.0*ratioRemain), len("100.00%")),
+				fmt.Sprintf("ETA %02d:%02d:%02d", secs/60/60, (secs/60)%60, secs%60))
+		}
+	}
 
+	tc := time.NewTicker(250 * time.Millisecond)
+	defer tc.Stop()
+	print()
 	for {
 		select {
-		case <-done:
+		case <-ctx.Done():
+			print()
 			fmt.Fprintln(os.Stderr)
 			return
-		case <-time.After(time.Second):
-			n := r.n.Load()
-			contentLengthStr := "???"
-			if contentLength > 0 {
-				contentLengthStr = fmt.Sprint(contentLength / 1024)
-			}
-
-			fmt.Fprintf(os.Stderr, "%s%s\t\t%s", vtRestartLine, padTruncateString(name, 36), padTruncateString(fmt.Sprintf("%d/%s kb", n/1024, contentLengthStr), 16))
-			if contentLength > 0 {
-				fmt.Fprintf(os.Stderr, "\t%.02f%%", float64(n)/float64(contentLength)*100)
-			} else {
-				fmt.Fprintf(os.Stderr, "\t-------%%")
-			}
-			if lastBytesRead > 0 {
-				fmt.Fprintf(os.Stderr, "\t%d kb/s", (n-lastBytesRead)/1024)
-			} else {
-				fmt.Fprintf(os.Stderr, "\t-------")
-			}
-			lastBytesRead = n
+		case <-tc.C:
+			print()
 		}
 	}
 }
 
-func padTruncateString(str string, truncateAt int) string {
-	if len(str) <= truncateAt {
-		return str + strings.Repeat(" ", truncateAt-len(str))
-	}
+func leftPad(s string, n int) string {
+	s = truncateString(s, n)
+	return strings.Repeat(" ", max(n-len(s), 0)) + s
+}
 
-	// Truncate the string, but respect unicode codepoint boundaries.
-	// As of RFC3629 utf-8 codepoints can be at most 4 bytes wide.
-	for i := 1; i <= 4 && i < len(str)-truncateAt; i++ {
-		if utf8.ValidString(str[:truncateAt-i]) {
-			return str[:truncateAt-i] + "…"
-		}
+func rightPad(s string, n int) string {
+	s = truncateString(s, n)
+	return s + strings.Repeat(" ", max(n-len(s), 0))
+}
+
+func truncateString(s string, n int) string {
+	if len(s) <= n {
+		return s
+	}
+	return truncate.String(s, max(n-1, 0)) + "…"
+}
+
+func formatIEC(n float64, unit string) string {
+	switch {
+	case n < 1<<10:
+		return fmt.Sprintf("%0.2f%s", n/(1<<0), unit)
+	case n < 1<<20:
+		return fmt.Sprintf("%0.2fKi%s", n/(1<<10), unit)
+	case n < 1<<30:
+		return fmt.Sprintf("%0.2fMi%s", n/(1<<20), unit)
+	case n < 1<<40:
+		return fmt.Sprintf("%0.2fGi%s", n/(1<<30), unit)
+	default:
+		return fmt.Sprintf("%0.2fTi%s", n/(1<<40), unit)
 	}
-	return "" // Should be unreachable
 }
 
 func getTargetStableID(ctx context.Context, ipStr string) (id tailcfg.StableNodeID, isOffline bool, err error) {

cmd/tailscale/depaware.txt

@@ -158,6 +158,7 @@ tailscale.com/cmd/tailscale dependencies: (generated by github.com/tailscale/dep
         tailscale.com/util/singleflight                              from tailscale.com/net/dnscache
         tailscale.com/util/slicesx                                   from tailscale.com/net/dnscache+
         tailscale.com/util/testenv                                   from tailscale.com/cmd/tailscale/cli
+        tailscale.com/util/truncate                                  from tailscale.com/cmd/tailscale/cli
         tailscale.com/util/vizerror                                  from tailscale.com/types/ipproto+
      💣 tailscale.com/util/winutil                                   from tailscale.com/hostinfo+
    W 💣 tailscale.com/util/winutil/authenticode                      from tailscale.com/clientupdate