I want to replace haproxy with traefik. But in order to that, I have to replace a Lua script which handles authentication (via auth token calling a rest API) and custom redirect (certain docker service) depending on headers and authentication from before. Is there an (easy) way to that?
Right now as for migrating I was thinking to leave haproxy for now and routing all valid traffic to traefik.
Authentication and Traefik is not an easy thing. At my company, we just switched back from Traefik to nginx since handling ldap/kerberos/pki etc. With Traefik can be painfully awkward. There is the possibility to pass authentication on from Traefik to a 3rd party and collect the session token or other relevant information using Forward Auth, so maybe take a look at that. You can also use BasicAuth Although getting it to run with your setup might prove hacky.