Throttler implements a leaky bucket request throttling algorithm where the duration between two requests is never less than the MinInterval

throttler.go

type ThrottleEngine struct {
	// The key to this map represents a unique user being throttled, such as
	// an api key, or some user identification obtained from a header
	MostRecentRequest map[string]time.Time
	MinInterval       time.Duration
	M                 *sync.Mutex
}

type HttpHandlerFunc func(http.ResponseWriter, *http.Request)

// Throttler implements a leaky bucket request throttling algorithm where the 
// duration between two requests is never less than the MinInterval
func Throttler(next HttpHandlerFunc, te *ThrottleEngine, header string) HttpHandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		k := r.Header.Get(header)
		te.M.Lock()
		defer te.M.Unlock()
		if lr, ok := te.MostRecentRequest[k]; ok {
			if time.Now().Sub(lr) < te.MinInterval {
				<-time.NewTimer(lr.Add(te.MinInterval).Sub(time.Now())).C
			}
		}
		te.MostRecentRequest[k] = time.Now()
		next(w, r)
	}
}