Method NewHandler

cpu.go:153–186

NewHandler returns a http handler allowing the profiler to be exposed on a pprof-compatible http endpoint. The sample rate is a value between 0 and 1 used to scale the profile results based on the sampling rate applied to the profiler so the resulting values remain representative. The symbolizer p

(sampleRate float64)

// The symbolizer passed as argument is used to resolve names of program
// locations recorded in the profile.
func (p *CPUProfiler) NewHandler(sampleRate float64) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		duration := 30 * time.Second

		if seconds := r.FormValue("seconds"); seconds != "" {
			n, err := strconv.ParseInt(seconds, 10, 64)
			if err == nil && n > 0 {
				duration = time.Duration(n) * time.Second
			}
		}

		ctx := r.Context()
		deadline, ok := ctx.Deadline()
		if ok {
			if timeout := time.Until(deadline); duration > timeout {
				serveError(w, http.StatusBadRequest, "profile duration exceeds server's WriteTimeout")
				return
			}
		}

		if !p.StartProfile() {
			serveError(w, http.StatusInternalServerError, "Could not enable CPU profiling: profiler already running")
			return
		}

		timer := time.NewTimer(duration)
		select {
		case <-timer.C:
		case <-ctx.Done():
		}
		timer.Stop()
		serveProfile(w, p.StopProfile(sampleRate))
	})
}

// NewFunctionListener returns a function listener suited to record CPU timings
// of calls to the function passed as argument.