@Override
            protected Double nullGaugeValue() {
                return 0.0;
            }
Returns a newly-created {@link DropwizardMeterRegistry} instance with the specified
{@link MetricRegistry}, {@link HierarchicalNameMapper} and {@link Clock}.
core/src/main/java/com/linecorp/armeria/common/metric/DropwizardMeterRegistries.java