@Override
    protected void update(Sample sample, MetricConfig config, double value, long now) {
        super.update(sample, config, 1.0, now);
    }
A {@link SampledStat} that maintains a simple count of what it has seen.
This is a special kind of {@link WindowedSum} that always records a value of {@code 1} instead of the provided value.
In other words, it counts the number of
{@link WindowedCount#record(MetricConfig, double, long)} invocations,
instead of summing the recorded values.

See also {@link CumulativeCount} for a non-sampled version of this metric.
clients/src/main/java/org/apache/kafka/common/metrics/stats/WindowedCount.java