the documentation contains the version, for which the documentation is valid - in your example it is 2.1 and 2.3. Always make sure the documentation matches with the elasticsearch version you are using.
In addition you are showing the documentation for the bulk API once and once for the update API. Again make sure you have the right docs for your API call. Yours looks like the update API.
The bulk API is consistent with all of its metadata parameters being prefixed with an underscore (whether that underscore is needed is a different issue, but for now it is there, so thats why retry_on_conflict has it as well).
Apache, Apache Lucene, Apache Hadoop, Hadoop, HDFS and the yellow elephant
logo are trademarks of the
Apache Software Foundation
in the United States and/or other countries.