@Override
    public IndexerPostProcessor addingService(
        ServiceReference<IndexerPostProcessor> serviceReference) {

      Registry registry = RegistryUtil.getRegistry();

      IndexerPostProcessor indexerPostProcessor = registry.getService(serviceReference);

      List<String> indexerClassNames =
          StringPlus.asList(serviceReference.getProperty("indexer.class.name"));

      for (String indexerClassName : indexerClassNames) {
        Indexer indexer = IndexerRegistryUtil.getIndexer(indexerClassName);

        if (indexer == null) {
          _log.error("No indexer for " + indexerClassName + " was found");

          continue;
        }

        indexer.registerIndexerPostProcessor(indexerPostProcessor);
      }

      return indexerPostProcessor;
    }