More Powerful Go Execution Tracing
More Powerful Go Execution Tracing runtime/trace golang.org/x/exp/trace Flight Recording // Set up the flight recorder fr := trace.NewFlightRecorder() fr.Start() // Set up and run the HTTP server var once sync.Once http.HandleFunc("/my-endpoint", func(w http.ResponseWriter, r *http.Request) { start := time.Now() // Do some work doWork(w, r) // Got a long-running request, take a snapshot if time.Since(start) > 300*time.Millisecond { // We only do this once for simplicity; you can do it multiple times once.Do(func() { // Capture snapshot var b bytes.Buffer _, err = fr.WriteTo(&b) if err != nil { log.Print(err) return } // Write snapshot to file if err := os.WriteFile("trace.out", b.Bytes(), 0o755); err != nil { log.Print(err) return } }) } }) log.Fatal(http.ListenAndServe(":8080", nil)) Trace Reader API // Start reading trace data from stdin. r, err := trace.NewReader(os.Stdin) if err != nil { log.Fatal(err) } var blocked int var blockedOnNetwork int for { // Read event ev, err := r.ReadEvent() if err == io.EOF { break } else if err != nil { log.Fatal(err) } // Handle it if ev.Kind() == trace.EventStateTransition { st := ev.StateTransition() if st.Resource.Kind == trace.ResourceGoroutine { id := st.Resource.Goroutine() from, to := st.GoroutineTransition() // Find blocked goroutines and count them if from.Executing() && to == trace.GoWaiting { blocked++ if strings.Contains(st.Reason, "network") { blockedOnNetwork++ } } } } } // Print the values we need p := 100 * float64(blockedOnNetwork) / float64(blocked) fmt.Printf("%2.3f%% instances of goroutines blocking were to block on the network\n", p)
