In the documentation for http-request, it mentions that:
It is important to know that http-request rules are processed very early in the HTTP processing, just after “block” rules and before “reqdel” or “reqrep” or “reqadd” rules.
so clearly there is an order of different directives, that has at least the sequence: block > http-request > reqdel/reqrep/reqadd, and from experimenting it seems use_backend comes after the req* rules. However, I’m having a hard time finding any other documentation on what the order is. Is there a complete list of what order different rules/actions happen in as a request is processed?