The "balance" keyword is not valid in a frontend section. From the
HAProxy documentation[1]:
balance <algorithm> [ <arguments> ]
balance url_param <param> [check_post [<max_wait>]]
Define the load balancing algorithm to be used in a backend.
May be used in sections : defaults | frontend | listen | backend
yes | no | yes | yes
When running HAProxy using the "split" template style, where a
frontend/backend pair are used instead of one listen section, HAProxy
will emit warnings for the Horizon config due to this.
[1]: https://www.haproxy.org/download/1.5/doc/configuration.txt
Closes-Bug: #1872540
Change-Id: I91cee275d91a51944298618493f4ea0cd80282cc
5c760df3d5