public String unitName() {
        return unit.name().substring(0, unit.name().length() - 2).toLowerCase(Locale.ROOT);
    }
The rate of the given quantity. By default this is the total observed over a set of samples from a sampled statistic
divided by the elapsed time over the sample windows. Alternative {@link SampledStat} implementations can be provided,
however, to record the rate of occurrences (e.g. the count of values measured over the time interval) or other such
values.
clients/src/main/java/org/apache/kafka/common/metrics/stats/Rate.java