@Override
            public Integer value() {
                return currentControllerId();
            }
Create a new LoaderMetrics object.

@param registry                      The metrics registry, or Optional.empty if this is a
                                     test and we don't have one.
@param batchProcessingTimeNsUpdater  Updates the batch processing time histogram.
@param batchSizesUpdater             Updates the batch sizes histogram.
metadata/src/main/java/org/apache/kafka/image/loader/metrics/MetadataLoaderMetrics.java