// Returns vulcan library compatible middleware
func (r *RateLimit) NewHandler(next http.Handler) (http.Handler, error) {
defaultRates := ratelimit.NewRateSet()
if err := defaultRates.Add(time.Duration(r.PeriodSeconds)*time.Second, r.Requests, r.Burst); err != nil {
return nil, err
}
return ratelimit.New(next, r.extract, defaultRates,
ratelimit.ExtractRates(r.extractRates), ratelimit.Clock(r.clock))
}
func makeRateExtractor(variable string) (ratelimit.RateExtractor, error) {
if variable == "" {
return nil, nil
}
if !strings.HasPrefix(variable, "request.header.") {
return nil, fmt.Errorf("unsupported variable format: %v", variable)
}
header := strings.TrimPrefix(variable, "request.header.")
if len(header) == 0 {
return nil, fmt.Errorf("Wrong header: %s", header)
}
return ratelimit.RateExtractorFunc(func(r *http.Request) (*ratelimit.RateSet, error) {
jsonString := r.Header.Get(header)
if jsonString == "" {
return nil, fmt.Errorf("empty rate header")
}
var specs []rateSpec
if err := json.Unmarshal([]byte(jsonString), &specs); err != nil {
return nil, err
}
rateSet := ratelimit.NewRateSet()
for _, s := range specs {
period := time.Duration(s.PeriodSeconds) * time.Second
if s.Burst == 0 {
s.Burst = s.Requests
}
if err := rateSet.Add(period, s.Requests, s.Burst); err != nil {
return nil, err
}
}
return rateSet, nil
}), nil
}