@Override
  public MetadataStore getMetadataStore(String namespace, Config config, MetricsRegistry metricsRegistry) {
    return new CoordinatorStreamStore(config, metricsRegistry);
  }
Builds the {@link CoordinatorStreamStore} based upon the provided {@link Config}
and {@link MetricsRegistry}.
samza-core/src/main/java/org/apache/samza/coordinator/metadatastore/CoordinatorStreamMetadataStoreFactory.java