src/cmd/trace/main.go - go - Git at Google

 // Copyright 2014 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.

 package main

 import (
 	"cmd/internal/browser"
 	"cmd/internal/telemetry"
 	"flag"
 	"fmt"
 	"internal/trace"
 	"internal/trace/raw"
 	"internal/trace/traceviewer"
 	"io"
 	"log"
 	"net"
 	"net/http"
 	_ "net/http/pprof" // Required to use pprof
 	"os"
 	"sync/atomic"
 	"time"
 )

 const usageMessage = "" +
 	`Usage of 'go tool trace':
 Given a trace file produced by 'go test':
 	go test -trace=trace.out pkg

 Open a web browser displaying trace:
 	go tool trace [flags] [pkg.test] trace.out

 Generate a pprof-like profile from the trace:
     go tool trace -pprof=TYPE [pkg.test] trace.out

 [pkg.test] argument is required for traces produced by Go 1.6 and below.
 Go 1.7 does not require the binary argument.

 Supported profile types are:
     - net: network blocking profile
     - sync: synchronization blocking profile
     - syscall: syscall blocking profile
     - sched: scheduler latency profile

 Flags:
 	-http=addr: HTTP service address (e.g., ':6060')
 	-pprof=type: print a pprof-like profile instead
 	-d=int: print debug info such as parsed events (1 for high-level, 2 for low-level)

 Note that while the various profiles available when launching
 'go tool trace' work on every browser, the trace viewer itself
 (the 'view trace' page) comes from the Chrome/Chromium project
 and is only actively tested on that browser.
 `

 var (
 	httpFlag  = flag.String("http", "localhost:0", "HTTP service address (e.g., ':6060')")
 	pprofFlag = flag.String("pprof", "", "print a pprof-like profile instead")
 	debugFlag = flag.Int("d", 0, "print debug information (1 for basic debug info, 2 for lower-level info)")

 	// The binary file name, left here for serveSVGProfile.
 	programBinary string
 	traceFile     string
 )

 func main() {
 	telemetry.Start()
 	flag.Usage = func() {
 		fmt.Fprint(os.Stderr, usageMessage)
 		os.Exit(2)
 	}
 	flag.Parse()
 	telemetry.Inc("trace/invocations")
 	telemetry.CountFlags("trace/flag:", *flag.CommandLine)

 	// Go 1.7 traces embed symbol info and does not require the binary.
 	// But we optionally accept binary as first arg for Go 1.5 traces.
 	switch flag.NArg() {
 	case 1:
 		traceFile = flag.Arg(0)
 	case 2:
 		programBinary = flag.Arg(0)
 		traceFile = flag.Arg(1)
 	default:
 		flag.Usage()
 	}

 	tracef, err := os.Open(traceFile)
 	if err != nil {
 		logAndDie(fmt.Errorf("failed to read trace file: %w", err))
 	}
 	defer tracef.Close()

 	// Get the size of the trace file.
 	fi, err := tracef.Stat()
 	if err != nil {
 		logAndDie(fmt.Errorf("failed to stat trace file: %v", err))
 	}
 	traceSize := fi.Size()

 	// Handle requests for profiles.
 	if *pprofFlag != "" {
 		parsed, err := parseTrace(tracef, traceSize)
 		if err != nil {
 			logAndDie(err)
 		}
 		var f traceviewer.ProfileFunc
 		switch *pprofFlag {
 		case "net":
 			f = pprofByGoroutine(computePprofIO(), parsed)
 		case "sync":
 			f = pprofByGoroutine(computePprofBlock(), parsed)
 		case "syscall":
 			f = pprofByGoroutine(computePprofSyscall(), parsed)
 		case "sched":
 			f = pprofByGoroutine(computePprofSched(), parsed)
 		default:
 			logAndDie(fmt.Errorf("unknown pprof type %s\n", *pprofFlag))
 		}
 		records, err := f(&http.Request{})
 		if err != nil {
 			logAndDie(fmt.Errorf("failed to generate pprof: %v\n", err))
 		}
 		if err := traceviewer.BuildProfile(records).Write(os.Stdout); err != nil {
 			logAndDie(fmt.Errorf("failed to generate pprof: %v\n", err))
 		}
 		logAndDie(nil)
 	}

 	// Debug flags.
 	switch *debugFlag {
 	case 1:
 		logAndDie(debugProcessedEvents(tracef))
 	case 2:
 		logAndDie(debugRawEvents(tracef))
 	}

 	ln, err := net.Listen("tcp", *httpFlag)
 	if err != nil {
 		logAndDie(fmt.Errorf("failed to create server socket: %w", err))
 	}
 	addr := "http://" + ln.Addr().String()

 	log.Print("Preparing trace for viewer...")
 	parsed, err := parseTraceInteractive(tracef, traceSize)
 	if err != nil {
 		logAndDie(err)
 	}
 	// N.B. tracef not needed after this point.
 	// We might double-close, but that's fine; we ignore the error.
 	tracef.Close()

 	// Print a nice message for a partial trace.
 	if parsed.err != nil {
 		log.Printf("Encountered error, but able to proceed. Error: %v", parsed.err)

 		lost := parsed.size - parsed.valid
 		pct := float64(lost) / float64(parsed.size) * 100
 		log.Printf("Lost %.2f%% of the latest trace data due to error (%s of %s)", pct, byteCount(lost), byteCount(parsed.size))
 	}

 	log.Print("Splitting trace for viewer...")
 	ranges, err := splitTrace(parsed)
 	if err != nil {
 		logAndDie(err)
 	}

 	log.Printf("Opening browser. Trace viewer is listening on %s", addr)
 	browser.Open(addr)

 	mutatorUtil := func(flags trace.UtilFlags) ([][]trace.MutatorUtil, error) {
 		return trace.MutatorUtilizationV2(parsed.events, flags), nil
 	}

 	mux := http.NewServeMux()

 	// Main endpoint.
 	mux.Handle("/", traceviewer.MainHandler([]traceviewer.View{
 		{Type: traceviewer.ViewProc, Ranges: ranges},
 		// N.B. Use the same ranges for threads. It takes a long time to compute
 		// the split a second time, but the makeup of the events are similar enough
 		// that this is still a good split.
 		{Type: traceviewer.ViewThread, Ranges: ranges},
 	}))

 	// Catapult handlers.
 	mux.Handle("/trace", traceviewer.TraceHandler())
 	mux.Handle("/jsontrace", JSONTraceHandler(parsed))
 	mux.Handle("/static/", traceviewer.StaticHandler())

 	// Goroutines handlers.
 	mux.HandleFunc("/goroutines", GoroutinesHandlerFunc(parsed.summary.Goroutines))
 	mux.HandleFunc("/goroutine", GoroutineHandler(parsed.summary.Goroutines))

 	// MMU handler.
 	mux.HandleFunc("/mmu", traceviewer.MMUHandlerFunc(ranges, mutatorUtil))

 	// Basic pprof endpoints.
 	mux.HandleFunc("/io", traceviewer.SVGProfileHandlerFunc(pprofByGoroutine(computePprofIO(), parsed)))
 	mux.HandleFunc("/block", traceviewer.SVGProfileHandlerFunc(pprofByGoroutine(computePprofBlock(), parsed)))
 	mux.HandleFunc("/syscall", traceviewer.SVGProfileHandlerFunc(pprofByGoroutine(computePprofSyscall(), parsed)))
 	mux.HandleFunc("/sched", traceviewer.SVGProfileHandlerFunc(pprofByGoroutine(computePprofSched(), parsed)))

 	// Region-based pprof endpoints.
 	mux.HandleFunc("/regionio", traceviewer.SVGProfileHandlerFunc(pprofByRegion(computePprofIO(), parsed)))
 	mux.HandleFunc("/regionblock", traceviewer.SVGProfileHandlerFunc(pprofByRegion(computePprofBlock(), parsed)))
 	mux.HandleFunc("/regionsyscall", traceviewer.SVGProfileHandlerFunc(pprofByRegion(computePprofSyscall(), parsed)))
 	mux.HandleFunc("/regionsched", traceviewer.SVGProfileHandlerFunc(pprofByRegion(computePprofSched(), parsed)))

 	// Region endpoints.
 	mux.HandleFunc("/userregions", UserRegionsHandlerFunc(parsed))
 	mux.HandleFunc("/userregion", UserRegionHandlerFunc(parsed))

 	// Task endpoints.
 	mux.HandleFunc("/usertasks", UserTasksHandlerFunc(parsed))
 	mux.HandleFunc("/usertask", UserTaskHandlerFunc(parsed))

 	err = http.Serve(ln, mux)
 	logAndDie(fmt.Errorf("failed to start http server: %w", err))
 }

 func logAndDie(err error) {
 	if err == nil {
 		os.Exit(0)
 	}
 	fmt.Fprintf(os.Stderr, "%s\n", err)
 	os.Exit(1)
 }

 func parseTraceInteractive(tr io.Reader, size int64) (parsed *parsedTrace, err error) {
 	done := make(chan struct{})
 	cr := countingReader{r: tr}
 	go func() {
 		parsed, err = parseTrace(&cr, size)
 		done <- struct{}{}
 	}()
 	ticker := time.NewTicker(5 * time.Second)
 progressLoop:
 	for {
 		select {
 		case <-ticker.C:
 		case <-done:
 			ticker.Stop()
 			break progressLoop
 		}
 		progress := cr.bytesRead.Load()
 		pct := float64(progress) / float64(size) * 100
 		log.Printf("%s of %s (%.1f%%) processed...", byteCount(progress), byteCount(size), pct)
 	}
 	return
 }

 type parsedTrace struct {
 	events      []trace.Event
 	summary     *trace.Summary
 	size, valid int64
 	err         error
 }

 func parseTrace(rr io.Reader, size int64) (*parsedTrace, error) {
 	// Set up the reader.
 	cr := countingReader{r: rr}
 	r, err := trace.NewReader(&cr)
 	if err != nil {
 		return nil, fmt.Errorf("failed to create trace reader: %w", err)
 	}

 	// Set up state.
 	s := trace.NewSummarizer()
 	t := new(parsedTrace)
 	var validBytes int64
 	var validEvents int
 	for {
 		ev, err := r.ReadEvent()
 		if err == io.EOF {
 			validBytes = cr.bytesRead.Load()
 			validEvents = len(t.events)
 			break
 		}
 		if err != nil {
 			t.err = err
 			break
 		}
 		t.events = append(t.events, ev)
 		s.Event(&t.events[len(t.events)-1])

 		if ev.Kind() == trace.EventSync {
 			validBytes = cr.bytesRead.Load()
 			validEvents = len(t.events)
 		}
 	}

 	// Check to make sure we got at least one good generation.
 	if validEvents == 0 {
 		return nil, fmt.Errorf("failed to parse any useful part of the trace: %v", t.err)
 	}

 	// Finish off the parsedTrace.
 	t.summary = s.Finalize()
 	t.valid = validBytes
 	t.size = size
 	t.events = t.events[:validEvents]
 	return t, nil
 }

 func (t *parsedTrace) startTime() trace.Time {
 	return t.events[0].Time()
 }

 func (t *parsedTrace) endTime() trace.Time {
 	return t.events[len(t.events)-1].Time()
 }

 // splitTrace splits the trace into a number of ranges, each resulting in approx 100 MiB of
 // json output (the trace viewer can hardly handle more).
 func splitTrace(parsed *parsedTrace) ([]traceviewer.Range, error) {
 	// TODO(mknyszek): Split traces by generation by doing a quick first pass over the
 	// trace to identify all the generation boundaries.
 	s, c := traceviewer.SplittingTraceConsumer(100 << 20) // 100 MiB
 	if err := generateTrace(parsed, defaultGenOpts(), c); err != nil {
 		return nil, err
 	}
 	return s.Ranges, nil
 }

 func debugProcessedEvents(trc io.Reader) error {
 	tr, err := trace.NewReader(trc)
 	if err != nil {
 		return err
 	}
 	for {
 		ev, err := tr.ReadEvent()
 		if err == io.EOF {
 			return nil
 		} else if err != nil {
 			return err
 		}
 		fmt.Println(ev.String())
 	}
 }

 func debugRawEvents(trc io.Reader) error {
 	rr, err := raw.NewReader(trc)
 	if err != nil {
 		return err
 	}
 	for {
 		ev, err := rr.ReadEvent()
 		if err == io.EOF {
 			return nil
 		} else if err != nil {
 			return err
 		}
 		fmt.Println(ev.String())
 	}
 }

 type countingReader struct {
 	r         io.Reader
 	bytesRead atomic.Int64
 }

 func (c *countingReader) Read(buf []byte) (n int, err error) {
 	n, err = c.r.Read(buf)
 	c.bytesRead.Add(int64(n))
 	return n, err
 }

 type byteCount int64

 func (b byteCount) String() string {
 	var suffix string
 	var divisor int64
 	switch {
 	case b < 1<<10:
 		suffix = "B"
 		divisor = 1
 	case b < 1<<20:
 		suffix = "KiB"
 		divisor = 1 << 10
 	case b < 1<<30:
 		suffix = "MiB"
 		divisor = 1 << 20
 	case b < 1<<40:
 		suffix = "GiB"
 		divisor = 1 << 30
 	}
 	if divisor == 1 {
 		return fmt.Sprintf("%d %s", b, suffix)
 	}
 	return fmt.Sprintf("%.1f %s", float64(b)/float64(divisor), suffix)
 }
	// Copyright 2014 The Go Authors. All rights reserved.
	// Use of this source code is governed by a BSD-style
	// license that can be found in the LICENSE file.

	package main

	import (
	"cmd/internal/browser"
	"cmd/internal/telemetry"
	"flag"
	"fmt"
	"internal/trace"
	"internal/trace/raw"
	"internal/trace/traceviewer"
	"io"
	"log"
	"net"
	"net/http"
	_ "net/http/pprof" // Required to use pprof
	"os"
	"sync/atomic"
	"time"
	)

	const usageMessage = "" +
	`Usage of 'go tool trace':
	Given a trace file produced by 'go test':
	go test -trace=trace.out pkg

	Open a web browser displaying trace:
	go tool trace [flags] [pkg.test] trace.out

	Generate a pprof-like profile from the trace:
	go tool trace -pprof=TYPE [pkg.test] trace.out

	[pkg.test] argument is required for traces produced by Go 1.6 and below.
	Go 1.7 does not require the binary argument.

	Supported profile types are:
	- net: network blocking profile
	- sync: synchronization blocking profile
	- syscall: syscall blocking profile
	- sched: scheduler latency profile

	Flags:
	-http=addr: HTTP service address (e.g., ':6060')
	-pprof=type: print a pprof-like profile instead
	-d=int: print debug info such as parsed events (1 for high-level, 2 for low-level)

	Note that while the various profiles available when launching
	'go tool trace' work on every browser, the trace viewer itself
	(the 'view trace' page) comes from the Chrome/Chromium project
	and is only actively tested on that browser.
	`

	var (
	httpFlag = flag.String("http", "localhost:0", "HTTP service address (e.g., ':6060')")
	pprofFlag = flag.String("pprof", "", "print a pprof-like profile instead")
	debugFlag = flag.Int("d", 0, "print debug information (1 for basic debug info, 2 for lower-level info)")

	// The binary file name, left here for serveSVGProfile.
	programBinary string
	traceFile string
	)

	func main() {
	telemetry.Start()
	flag.Usage = func() {
	fmt.Fprint(os.Stderr, usageMessage)
	os.Exit(2)
	}
	flag.Parse()
	telemetry.Inc("trace/invocations")
	telemetry.CountFlags("trace/flag:", *flag.CommandLine)

	// Go 1.7 traces embed symbol info and does not require the binary.
	// But we optionally accept binary as first arg for Go 1.5 traces.
	switch flag.NArg() {
	case 1:
	traceFile = flag.Arg(0)
	case 2:
	programBinary = flag.Arg(0)
	traceFile = flag.Arg(1)
	default:
	flag.Usage()
	}

	tracef, err := os.Open(traceFile)
	if err != nil {
	logAndDie(fmt.Errorf("failed to read trace file: %w", err))
	}
	defer tracef.Close()

	// Get the size of the trace file.
	fi, err := tracef.Stat()
	if err != nil {
	logAndDie(fmt.Errorf("failed to stat trace file: %v", err))
	}
	traceSize := fi.Size()

	// Handle requests for profiles.
	if *pprofFlag != "" {
	parsed, err := parseTrace(tracef, traceSize)
	if err != nil {
	logAndDie(err)
	}
	var f traceviewer.ProfileFunc
	switch *pprofFlag {
	case "net":
	f = pprofByGoroutine(computePprofIO(), parsed)
	case "sync":
	f = pprofByGoroutine(computePprofBlock(), parsed)
	case "syscall":
	f = pprofByGoroutine(computePprofSyscall(), parsed)
	case "sched":
	f = pprofByGoroutine(computePprofSched(), parsed)
	default:
	logAndDie(fmt.Errorf("unknown pprof type %s\n", *pprofFlag))
	}
	records, err := f(&http.Request{})
	if err != nil {
	logAndDie(fmt.Errorf("failed to generate pprof: %v\n", err))
	}
	if err := traceviewer.BuildProfile(records).Write(os.Stdout); err != nil {
	logAndDie(fmt.Errorf("failed to generate pprof: %v\n", err))
	}
	logAndDie(nil)
	}

	// Debug flags.
	switch *debugFlag {
	case 1:
	logAndDie(debugProcessedEvents(tracef))
	case 2:
	logAndDie(debugRawEvents(tracef))
	}

	ln, err := net.Listen("tcp", *httpFlag)
	if err != nil {
	logAndDie(fmt.Errorf("failed to create server socket: %w", err))
	}
	addr := "http://" + ln.Addr().String()

	log.Print("Preparing trace for viewer...")
	parsed, err := parseTraceInteractive(tracef, traceSize)
	if err != nil {
	logAndDie(err)
	}
	// N.B. tracef not needed after this point.
	// We might double-close, but that's fine; we ignore the error.
	tracef.Close()

	// Print a nice message for a partial trace.
	if parsed.err != nil {
	log.Printf("Encountered error, but able to proceed. Error: %v", parsed.err)

	lost := parsed.size - parsed.valid
	pct := float64(lost) / float64(parsed.size) * 100
	log.Printf("Lost %.2f%% of the latest trace data due to error (%s of %s)", pct, byteCount(lost), byteCount(parsed.size))
	}

	log.Print("Splitting trace for viewer...")
	ranges, err := splitTrace(parsed)
	if err != nil {
	logAndDie(err)
	}

	log.Printf("Opening browser. Trace viewer is listening on %s", addr)
	browser.Open(addr)

	mutatorUtil := func(flags trace.UtilFlags) ([][]trace.MutatorUtil, error) {
	return trace.MutatorUtilizationV2(parsed.events, flags), nil
	}

	mux := http.NewServeMux()

	// Main endpoint.
	mux.Handle("/", traceviewer.MainHandler([]traceviewer.View{
	{Type: traceviewer.ViewProc, Ranges: ranges},
	// N.B. Use the same ranges for threads. It takes a long time to compute
	// the split a second time, but the makeup of the events are similar enough
	// that this is still a good split.
	{Type: traceviewer.ViewThread, Ranges: ranges},
	}))

	// Catapult handlers.
	mux.Handle("/trace", traceviewer.TraceHandler())
	mux.Handle("/jsontrace", JSONTraceHandler(parsed))
	mux.Handle("/static/", traceviewer.StaticHandler())

	// Goroutines handlers.
	mux.HandleFunc("/goroutines", GoroutinesHandlerFunc(parsed.summary.Goroutines))
	mux.HandleFunc("/goroutine", GoroutineHandler(parsed.summary.Goroutines))

	// MMU handler.
	mux.HandleFunc("/mmu", traceviewer.MMUHandlerFunc(ranges, mutatorUtil))

	// Basic pprof endpoints.
	mux.HandleFunc("/io", traceviewer.SVGProfileHandlerFunc(pprofByGoroutine(computePprofIO(), parsed)))
	mux.HandleFunc("/block", traceviewer.SVGProfileHandlerFunc(pprofByGoroutine(computePprofBlock(), parsed)))
	mux.HandleFunc("/syscall", traceviewer.SVGProfileHandlerFunc(pprofByGoroutine(computePprofSyscall(), parsed)))
	mux.HandleFunc("/sched", traceviewer.SVGProfileHandlerFunc(pprofByGoroutine(computePprofSched(), parsed)))

	// Region-based pprof endpoints.
	mux.HandleFunc("/regionio", traceviewer.SVGProfileHandlerFunc(pprofByRegion(computePprofIO(), parsed)))
	mux.HandleFunc("/regionblock", traceviewer.SVGProfileHandlerFunc(pprofByRegion(computePprofBlock(), parsed)))
	mux.HandleFunc("/regionsyscall", traceviewer.SVGProfileHandlerFunc(pprofByRegion(computePprofSyscall(), parsed)))
	mux.HandleFunc("/regionsched", traceviewer.SVGProfileHandlerFunc(pprofByRegion(computePprofSched(), parsed)))

	// Region endpoints.
	mux.HandleFunc("/userregions", UserRegionsHandlerFunc(parsed))
	mux.HandleFunc("/userregion", UserRegionHandlerFunc(parsed))

	// Task endpoints.
	mux.HandleFunc("/usertasks", UserTasksHandlerFunc(parsed))
	mux.HandleFunc("/usertask", UserTaskHandlerFunc(parsed))

	err = http.Serve(ln, mux)
	logAndDie(fmt.Errorf("failed to start http server: %w", err))
	}

	func logAndDie(err error) {
	if err == nil {
	os.Exit(0)
	}
	fmt.Fprintf(os.Stderr, "%s\n", err)
	os.Exit(1)
	}

	func parseTraceInteractive(tr io.Reader, size int64) (parsed *parsedTrace, err error) {
	done := make(chan struct{})
	cr := countingReader{r: tr}
	go func() {
	parsed, err = parseTrace(&cr, size)
	done <- struct{}{}
	}()
	ticker := time.NewTicker(5 * time.Second)
	progressLoop:
	for {
	select {
	case <-ticker.C:
	case <-done:
	ticker.Stop()
	break progressLoop
	}
	progress := cr.bytesRead.Load()
	pct := float64(progress) / float64(size) * 100
	log.Printf("%s of %s (%.1f%%) processed...", byteCount(progress), byteCount(size), pct)
	}
	return
	}

	type parsedTrace struct {
	events []trace.Event
	summary *trace.Summary
	size, valid int64
	err error
	}

	func parseTrace(rr io.Reader, size int64) (*parsedTrace, error) {
	// Set up the reader.
	cr := countingReader{r: rr}
	r, err := trace.NewReader(&cr)
	if err != nil {
	return nil, fmt.Errorf("failed to create trace reader: %w", err)
	}

	// Set up state.
	s := trace.NewSummarizer()
	t := new(parsedTrace)
	var validBytes int64
	var validEvents int
	for {
	ev, err := r.ReadEvent()
	if err == io.EOF {
	validBytes = cr.bytesRead.Load()
	validEvents = len(t.events)
	break
	}
	if err != nil {
	t.err = err
	break
	}
	t.events = append(t.events, ev)
	s.Event(&t.events[len(t.events)-1])

	if ev.Kind() == trace.EventSync {
	validBytes = cr.bytesRead.Load()
	validEvents = len(t.events)
	}
	}

	// Check to make sure we got at least one good generation.
	if validEvents == 0 {
	return nil, fmt.Errorf("failed to parse any useful part of the trace: %v", t.err)
	}

	// Finish off the parsedTrace.
	t.summary = s.Finalize()
	t.valid = validBytes
	t.size = size
	t.events = t.events[:validEvents]
	return t, nil
	}

	func (t *parsedTrace) startTime() trace.Time {
	return t.events[0].Time()
	}

	func (t *parsedTrace) endTime() trace.Time {
	return t.events[len(t.events)-1].Time()
	}

	// splitTrace splits the trace into a number of ranges, each resulting in approx 100 MiB of
	// json output (the trace viewer can hardly handle more).
	func splitTrace(parsed *parsedTrace) ([]traceviewer.Range, error) {
	// TODO(mknyszek): Split traces by generation by doing a quick first pass over the
	// trace to identify all the generation boundaries.
	s, c := traceviewer.SplittingTraceConsumer(100 << 20) // 100 MiB
	if err := generateTrace(parsed, defaultGenOpts(), c); err != nil {
	return nil, err
	}
	return s.Ranges, nil
	}

	func debugProcessedEvents(trc io.Reader) error {
	tr, err := trace.NewReader(trc)
	if err != nil {
	return err
	}
	for {
	ev, err := tr.ReadEvent()
	if err == io.EOF {
	return nil
	} else if err != nil {
	return err
	}
	fmt.Println(ev.String())
	}
	}

	func debugRawEvents(trc io.Reader) error {
	rr, err := raw.NewReader(trc)
	if err != nil {
	return err
	}
	for {
	ev, err := rr.ReadEvent()
	if err == io.EOF {
	return nil
	} else if err != nil {
	return err
	}
	fmt.Println(ev.String())
	}
	}

	type countingReader struct {
	r io.Reader
	bytesRead atomic.Int64
	}

	func (c *countingReader) Read(buf []byte) (n int, err error) {
	n, err = c.r.Read(buf)
	c.bytesRead.Add(int64(n))
	return n, err
	}

	type byteCount int64

	func (b byteCount) String() string {
	var suffix string
	var divisor int64
	switch {
	case b < 1<<10:
	suffix = "B"
	divisor = 1
	case b < 1<<20:
	suffix = "KiB"
	divisor = 1 << 10
	case b < 1<<30:
	suffix = "MiB"
	divisor = 1 << 20
	case b < 1<<40:
	suffix = "GiB"
	divisor = 1 << 30
	}
	if divisor == 1 {
	return fmt.Sprintf("%d %s", b, suffix)
	}
	return fmt.Sprintf("%.1f %s", float64(b)/float64(divisor), suffix)
	}