protected static IndexRequestFactory getIndexRequestFactory(ElasticsearchConfig config) {
    if (config.getIndexRequestFactoryClassName().isPresent()) {
      return ReflectionUtil.getObj(config.getIndexRequestFactoryClassName().get(), IndexRequestFactory.class);
    } else {
      return new DefaultIndexRequestFactory();
    }
  }
A {@link SystemFactory} for Elasticsearch.

<p>This only supports the {@link SystemProducer} so all other methods return an
{@link UnsupportedOperationException}
samza-elasticsearch/src/main/java/org/apache/samza/system/elasticsearch/ElasticsearchSystemFactory.java