[RFE] haproxy option httpchk flexibility wish list

[Eric Miller]

Kolla-ansible master as of 2018/9/26

As mentioned, this is a wish list item. I'll provide my updates if I have time to implement.

The /usr/share/kolla-ansible/ansible/roles/haproxy/defaults/main.yml file has an haproxy_listen_http_extra option which will insert parameters into the haproxy listeners, but it inserts the same parameters for "all" services.

A common check would be "option httpchk" to be sure that a valid response, such as a 2xx or 3xx HTTP response is being returned. However, many services respond with a 4xx response legitimately (such as Swift proxies when unauthenticated), so a general "option httpchk" causes many services to fail.

It would be nice to have specific haproxy_listen_http_extra options "per service", so custom options can be provided per service, depending on the need. For example, it is quite important that keystone return a 2xx. When it dies, it returns a 500 Internal Server error, which is not caught by haproxy in its current Kolla-Ansible configuration, so with 5 controllers, every 5th request fails with a 500 error.

So, the only fail-over condition that is measured today is "no response".

Eric