code: public static CompressionCodec getGzipCodec(Configuration conf) {
          try {
              return (CompressionCodec) ReflectionUtils.newInstance(
                  conf.getClassByName("org.apache.hadoop.io.compress.GzipCodec").asSubclass(CompressionCodec.class),
                  conf);
          } catch (ClassNotFoundException e) {
              logger.warn("GzipCodec could not be instantiated", e);
              return null;
          }
      }
docs: Instantiates a Hadoop codec for compressing and decompressing Gzip files. This is the
  most common compression applied to WARC files.
  
  @param conf The Hadoop configuration.