in metrics.go [192:201]
func (mh MetricsHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
w.Header().Set("Content-Type", "application/json")
if r.Method == "GET" {
mh.handleMetricsQuery(w, r)
} else {
mh.handleMetricsSave(w, r)
}
return
}