// 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/trace.Start
- 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()) {
fmt.Fprintf(os.Stderr, "Trace viewer is listening on http://%s\n", ln.Addr().String())
}
// 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
}
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(`
View trace
Goroutine analysis
Network blocking profile
Synchronization blocking profile
Syscall blocking profile
Scheduler latency profile
`)
// 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)
}