Function WaitForServer

ch5/wait/wait.go:21–33

!+ WaitForServer attempts to contact the server of a URL. It tries for one minute using exponential back-off. It reports an error if all attempts fail.

(url string)

// It tries for one minute using exponential back-off.
// It reports an error if all attempts fail.
func WaitForServer(url string) error {
	const timeout = 1 * time.Minute
	deadline := time.Now().Add(timeout)
	for tries := 0; time.Now().Before(deadline); tries++ {
		_, err := http.Head(url)
		if err == nil {
			return nil // success
		}
		log.Printf("server not responding (%s); retrying...", err)
		time.Sleep(time.Second << uint(tries)) // exponential back-off
	}
	return fmt.Errorf("server %s failed to respond after %s", url, timeout)
}

//!-