private void setTimeToFirstByteFirstTime() {
        boolean isFirstWrite = firstSetOfTimeToFirstByte.getAndSet(false);
        if (isFirstWrite) {
            long timeToFirstByte = getRequestLatency();
            metric.set(MetricDefinitions.TIME_TO_FIRST_BYTE, timeToFirstByte, context);
        }
    }
Responsible for metric reporting for JDisc http request handler support.
@author Tony Vaagenes
container-core/src/main/java/com/yahoo/jdisc/http/server/jetty/RequestMetricReporter.java