cmd/trace: add new command

Trace command allows to visualize and analyze traces. Run as: $ go tool trace binary trace.file The commands opens web browser with the main page, which contains links for trace visualization, blocking profiler, network IO profiler and per-goroutine traces. Also move trace parser from runtime/pprof/trace_parser_test.go to internal/trace/parser.go, so that it can be shared between tests and the command. Change-Id: Ic97ed59ad6e4c7e1dc9eca5e979701a2b4aed7cf Reviewed-on: https://go-review.googlesource.com/3601 Reviewed-by: Andrew Gerrand <adg@golang.org>
2025-12-08 06:10:04 +00:00 · 2015-01-30 13:31:43 +03:00 · 2015-01-30 13:31:43 +03:00 · edadffa2f3
commit edadffa2f3
parent 58125ffe73
11 changed files with 4768 additions and 666 deletions
--- a/src/cmd/trace/main.go
+++ b/src/cmd/trace/main.go
@ -0,0 +1,156 @@
+// 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.
+
+/*
+Trace is a tool for viewing trace files.
+
+Trace files can be generated with:
+	- runtime/pprof.StartTrace
+	- net/http/pprof package
+	- go test -trace
+
+Example usage:
+Generate a trace file with 'go test':
+	go test -trace trace.out pkg
+View the trace in a web browser:
+	go tool trace pkg.test trace.out
+*/
+package main
+
+import (
+	"bufio"
+	"flag"
+	"fmt"
+	"internal/trace"
+	"net"
+	"net/http"
+	"os"
+	"os/exec"
+	"runtime"
+	"sync"
+)
+
+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
+
+Flags:
+	-http=addr: HTTP service address (e.g., ':6060')
+`
+
+var (
+	httpFlag = flag.String("http", "localhost:0", "HTTP service address (e.g., ':6060')")
+
+	// The binary file name, left here for serveSVGProfile.
+	programBinary string
+	traceFile     string
+)
+
+func main() {
+	flag.Usage = func() {
+		fmt.Fprintln(os.Stderr, usageMessage)
+		os.Exit(2)
+	}
+	flag.Parse()
+
+	// Usage information when no arguments.
+	if flag.NArg() != 2 {
+		flag.Usage()
+	}
+	programBinary = flag.Arg(0)
+	traceFile = flag.Arg(1)
+
+	ln, err := net.Listen("tcp", *httpFlag)
+	if err != nil {
+		dief("failed to create server socket: %v\n", err)
+	}
+	// Open browser.
+	if !startBrowser("http://" + ln.Addr().String()) {
+		dief("failed to start browser\n")
+	}
+
+	// Parse and symbolize trace asynchronously while browser opens.
+	go parseEvents()
+
+	// Start http server.
+	http.HandleFunc("/", httpMain)
+	err = http.Serve(ln, nil)
+	dief("failed to start http server: %v\n", err)
+}
+
+var loader struct {
+	once   sync.Once
+	events []*trace.Event
+	err    error
+}
+
+func parseEvents() ([]*trace.Event, error) {
+	loader.once.Do(func() {
+		tracef, err := os.Open(flag.Arg(1))
+		if err != nil {
+			loader.err = fmt.Errorf("failed to open trace file: %v", err)
+			return
+		}
+		defer tracef.Close()
+
+		// Parse and symbolize.
+		events, err := trace.Parse(bufio.NewReader(tracef))
+		if err != nil {
+			loader.err = fmt.Errorf("failed to parse trace: %v", err)
+			return
+		}
+		err = trace.Symbolize(events, programBinary)
+		if err != nil {
+			loader.err = fmt.Errorf("failed to symbolize trace: %v", err)
+			return
+		}
+		loader.events = events
+	})
+	return loader.events, loader.err
+}
+
+// httpMain serves the starting page.
+func httpMain(w http.ResponseWriter, r *http.Request) {
+	w.Write(templMain)
+}
+
+var templMain = []byte(`
+<html>
+<body>
+<a href="/trace">View trace</a><br>
+<a href="/goroutines">Goroutine analysis</a><br>
+<a href="/io">IO blocking profile</a><br>
+<a href="/block">Synchronization blocking profile</a><br>
+<a href="/syscall">Syscall blocking profile</a><br>
+<a href="/sched">Scheduler latency profile</a><br>
+</body>
+</html>
+`)
+
+// startBrowser tries to open the URL in a browser
+// and reports whether it succeeds.
+// Note: copied from x/tools/cmd/cover/html.go
+func startBrowser(url string) bool {
+	// try to start the browser
+	var args []string
+	switch runtime.GOOS {
+	case "darwin":
+		args = []string{"open"}
+	case "windows":
+		args = []string{"cmd", "/c", "start"}
+	default:
+		args = []string{"xdg-open"}
+	}
+	cmd := exec.Command(args[0], append(args[1:], url)...)
+	return cmd.Start() == nil
+}
+
+func dief(msg string, args ...interface{}) {
+	fmt.Fprintf(os.Stderr, msg, args...)
+	os.Exit(1)
+}