code: protected ObjectMetadata getObjectMetadata(String key) {
      try {
        ObjectMetadata meta = mClient.getObjectMetadata(mBucket, key);
        return meta;
      } catch (AmazonClientException e) {
        LOG.debug(e.getMessage());
        return null;
      }
    }
docs: Request object metadata, Used to call _SUCCESS object or identify if objects
  were generated by Stocator
  
  @param key key
  @return the metadata