More Powerful Go Execution Tracing

Tue, 07 May 2024 11:45:57 +0800

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)

Trace on Ricky

More Powerful Go Execution Tracing

runtime/trace

golang.org/x/exp/trace

Flight Recording

Trace Reader API