Configuring HAProxy in docker (503 Service Unavailable)

Question

I create an Octoprint container to control my printer, and it works fine. Now I want to have secure access to it from anywhere. To do this, I use HAProxy.
However, after authorization, HAProxy returns the StatusCode 503, and I can't fix that.
Here are the docker files and configuration file:

docker-compose.yml

version: "2.5"

services:
  haproxy:
    build:
      context: .
      dockerfile: haproxy/Dockerfile
    container_name: haproxy
    image: haproxy:latest
    restart: always
    volumes:
      - haproxy_conf:/usr/local/etc/haproxy/
    ports:
      - 80:80
    depends_on:
      - octoprint
    networks:
      - haproxy_net

  octoprint:
    restart: unless-stopped
    image: octoprint/octoprint
    container_name: octoprint
    ports:
      - 5521:80
    networks:
      - haproxy_net
    volumes:
      - octoprint:/octoprint

volumes:
  haproxy_conf:
  octoprint:

networks:
  haproxy_net:
    driver: bridge

haproxy\haproxy.cfg

global
        maxconn 4096
        user haproxy
        group haproxy
        daemon
        log 127.0.0.1 local1 debug
 
defaults
        log     global
        mode    http
        option  httplog
        option  dontlognull
        retries 3
        option redispatch
        option http-server-close
        option forwardfor
        maxconn 2000
        timeout connect 5s
        timeout client  15m
        timeout server  15m
 
frontend public
        bind *:80 v4v6
        default_backend octoprint
 
backend octoprint
        http-request replace-path ^([^\ :]*)\ /(.*) \1\ /\2
        option forwardfor
        server octoprint1 octoprint:5521
        acl AuthOkay http_auth(L1)
        http-request auth realm octoprint if !AuthOkay
 
userlist L1
        user UserName insecure-password Password

haproxy\Dockerfile

FROM haproxy:latest
COPY haproxy/haproxy.cfg /usr/local/etc/haproxy/haproxy.cfg

Answer 1

You're using configuration directives that are not supported in the old HAProxy 1.8 version bundled in Octopi.

Specifically http-request replace-path. replace-path was introduced in HAproxy 2.1 or 2.2. So you'll need to upgrade it before your config will work.

I've been hunting for pre-built haproxy 2.2+ binary for RPi's ARM architecture myself for a while now, but I think it's down to building it ourselves. I'm going to be trying for 2.4 sometime soon, since ARM build support exists in the HAproxy source.