HAProxy supports more health check protocols than just HTTP, we should make these available in VyOS reverse-proxy configuration.
Example of how this could be configured in VyOS:
set load-balancing reverse-proxy backend bk-01 health-check ldap set load-balancing reverse-proxy backend bk-01 health-check redis set load-balancing reverse-proxy backend bk-01 health-check mysql set load-balancing reverse-proxy backend bk-01 health-check pgsql set load-balancing reverse-proxy backend bk-01 health-check smtp
This would then render in haproxy.cfg the corresponding option:
backend bk-01
option ldap-check
option redis-check
option mysql-check
option pgsql-check
option smtpchk