Currently ES is on version 0.19.8 for YCSB and does not work out of the box (confirmed on fedora 23)
I currently have a pull request for it here: https://github.com/brianfrankcooper/YCSB/pull/552.
I'd like to know if v1.x versions are still being benchmarked with YCSB. If not, bumping it to v 2.x per the pull request would be the best route.
If v 1.x are being benchmarked, please advise what the next best step is.