src/cmd/trace/main.go

// 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 (
	"bufio"
	"cmd/internal/browser"
	"flag"
	"fmt"
	"html/template"
	"internal/trace"
	"io"
	"log"
	"net"
	"net/http"
	"os"
	"runtime"
	"runtime/debug"
	"sync"

	_ "net/http/pprof" // Required to use pprof
)

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: print debug info such as parsed events

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.Bool("d", false, "print debug information such as parsed events list")

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

func main() {
	flag.Usage = func() {
		fmt.Fprint(os.Stderr, usageMessage)
		os.Exit(2)
	}
	flag.Parse()

	// 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()
	}

	var pprofFunc func(io.Writer, *http.Request) error
	switch *pprofFlag {
	case "net":
		pprofFunc = pprofByGoroutine(computePprofIO)
	case "sync":
		pprofFunc = pprofByGoroutine(computePprofBlock)
	case "syscall":
		pprofFunc = pprofByGoroutine(computePprofSyscall)
	case "sched":
		pprofFunc = pprofByGoroutine(computePprofSched)
	}
	if pprofFunc != nil {
		if err := pprofFunc(os.Stdout, &http.Request{}); err != nil {
			dief("failed to generate pprof: %v\n", err)
		}
		os.Exit(0)
	}
	if *pprofFlag != "" {
		dief("unknown pprof type %s\n", *pprofFlag)
	}

	ln, err := net.Listen("tcp", *httpFlag)
	if err != nil {
		dief("failed to create server socket: %v\n", err)
	}

	log.Print("Parsing trace...")
	res, err := parseTrace()
	if err != nil {
		dief("%v\n", err)
	}

	if *debugFlag {
		trace.Print(res.Events)
		os.Exit(0)
	}
	reportMemoryUsage("after parsing trace")
	debug.FreeOSMemory()

	log.Print("Splitting trace...")
	ranges = splitTrace(res)
	reportMemoryUsage("after spliting trace")
	debug.FreeOSMemory()

	addr := "http://" + ln.Addr().String()
	log.Printf("Opening browser. Trace viewer is listening on %s", addr)
	browser.Open(addr)

	// Start http server.
	http.HandleFunc("/", httpMain)
	err = http.Serve(ln, nil)
	dief("failed to start http server: %v\n", err)
}

var ranges []Range

var loader struct {
	once sync.Once
	res  trace.ParseResult
	err  error
}

// parseEvents is a compatibility wrapper that returns only
// the Events part of trace.ParseResult returned by parseTrace.
func parseEvents() ([]*trace.Event, error) {
	res, err := parseTrace()
	if err != nil {
		return nil, err
	}
	return res.Events, err
}

func parseTrace() (trace.ParseResult, error) {
	loader.once.Do(func() {
		tracef, err := os.Open(traceFile)
		if err != nil {
			loader.err = fmt.Errorf("failed to open trace file: %v", err)
			return
		}
		defer tracef.Close()

		// Parse and symbolize.
		res, err := trace.Parse(bufio.NewReader(tracef), programBinary)
		if err != nil {
			loader.err = fmt.Errorf("failed to parse trace: %v", err)
			return
		}
		loader.res = res
	})
	return loader.res, loader.err
}

// httpMain serves the starting page.
func httpMain(w http.ResponseWriter, r *http.Request) {
	if err := templMain.Execute(w, ranges); err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}
}

var templMain = template.Must(template.New("").Parse(`
<html>
<body>
{{if $}}
	{{range $e := $}}
		<a href="{{$e.URL}}">View trace ({{$e.Name}})</a><br>
	{{end}}
	<br>
{{else}}
	<a href="/trace">View trace</a><br>
{{end}}
<a href="/goroutines">Goroutine analysis</a><br>
<a href="/io">Network blocking profile</a> (<a href="/io?raw=1" download="io.profile">⬇</a>)<br>
<a href="/block">Synchronization blocking profile</a> (<a href="/block?raw=1" download="block.profile">⬇</a>)<br>
<a href="/syscall">Syscall blocking profile</a> (<a href="/syscall?raw=1" download="syscall.profile">⬇</a>)<br>
<a href="/sched">Scheduler latency profile</a> (<a href="/sche?raw=1" download="sched.profile">⬇</a>)<br>
<a href="/usertasks">User-defined tasks</a><br>
<a href="/userregions">User-defined regions</a><br>
<a href="/mmu">Minimum mutator utilization</a><br>
</body>
</html>
`))

func dief(msg string, args ...any) {
	fmt.Fprintf(os.Stderr, msg, args...)
	os.Exit(1)
}

var debugMemoryUsage bool

func init() {
	v := os.Getenv("DEBUG_MEMORY_USAGE")
	debugMemoryUsage = v != ""
}

func reportMemoryUsage(msg string) {
	if !debugMemoryUsage {
		return
	}
	var s runtime.MemStats
	runtime.ReadMemStats(&s)
	w := os.Stderr
	fmt.Fprintf(w, "%s\n", msg)
	fmt.Fprintf(w, " Alloc:\t%d Bytes\n", s.Alloc)
	fmt.Fprintf(w, " Sys:\t%d Bytes\n", s.Sys)
	fmt.Fprintf(w, " HeapReleased:\t%d Bytes\n", s.HeapReleased)
	fmt.Fprintf(w, " HeapSys:\t%d Bytes\n", s.HeapSys)
	fmt.Fprintf(w, " HeapInUse:\t%d Bytes\n", s.HeapInuse)
	fmt.Fprintf(w, " HeapAlloc:\t%d Bytes\n", s.HeapAlloc)
	var dummy string
	fmt.Printf("Enter to continue...")
	fmt.Scanf("%s", &dummy)
}