public static DropwizardMeterRegistry newRegistry(MetricRegistry registry,
                                                      HierarchicalNameMapper nameMapper,
                                                      Clock clock) {
        final DropwizardMeterRegistry meterRegistry = new DropwizardMeterRegistry(
                DEFAULT_DROPWIZARD_CONFIG,
                requireNonNull(registry, "registry"),
                requireNonNull(nameMapper, "nameMapper"),
                requireNonNull(clock, "clock")) {

            @Override
            protected Double nullGaugeValue() {
                return 0.0;
            }
        };

        return configureRegistry(meterRegistry);
    }
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