in concurrency-loadbalancer-m3/src/main/java/com/uber/concurrency/loadbalancer/TallyMetricsTaskListener.java [133:140]
private double calcStandardDeviation(Function<EWMARates, EWMA> mapper) {
double[] rates = taskRates.values().stream()
.map(mapper)
.map(o->o.getRate(TimeUnit.SECONDS))
.mapToDouble(d->d)
.toArray();
return STANDARD_DEVIATION.evaluate(rates);
}