WordPress on Traefik (path-based routing) → wp-admin causes ERR_TOO_MANY_REDIRECTS

Traefik Traefik v3 (latest)
1

I’m deploying multiple WordPress instances for each GitLab merge request. I cannot use subdomains; each instance lives under a unique path prefix on the same host/port.

Examples:

https://test.domain.com:18086/x/y/mr1/wordpress/
https://test.domain.com:18086/x/y/mr2/wordpress/

Stack: Docker, Traefik v2, Nginx, WordPress.

What changed / Current problem
Originally, hitting https://test.domain.com:18086/x/y/mr1/wordpress//wp-admin/ redirected to the root (https://test.domain.com:18086/wp-admin).
After adjusting my configuration, the URL stays under the correct prefix, but now the browser shows ERR_TOO_MANY_REDIRECTS.

This happens both on the test server and on localhost.

On localhost, the only working workaround is to remove Traefik completely and add this to .htaccess:

RewriteRule ^x/y/mr1/(.*) /$1 [L]

This fixes wp-admin, but I want to solve it cleanly through Traefik.

Compose service (simplified)

wordpress:
  build:
    context: ../
    dockerfile: ./build/wordpress/Dockerfile
    args:
      DIST: ./build/wordpress
      TOOLS: ./tools
      WP_PATH_PREFIX: ${WP_PATH_PREFIX}
  container_name: ${MR_NAME}-wordpress
  restart: always
  depends_on:
    wp_db:
      condition: service_healthy
  networks:
    - wp_internal
    - traefik_wordpress_backend
  environment:
    WP_PATH_PREFIX: ${WP_PATH_PREFIX}
    WORDPRESS_DB_HOST: wp_db
    WORDPRESS_DB_USER: ${WP_DB_USER}
    WORDPRESS_DB_PASSWORD: ${WP_DB_PASS}
    WORDPRESS_DB_NAME: ${WP_DB_NAME}
    WORDPRESS_CONFIG_EXTRA: |
      define('WP_HOME', '${WP_URL}');
      define('WP_SITEURL', '${WP_CUSTOM_SITEURL}');
      define('FORCE_SSL_ADMIN', ${FORCE_SSL_ADMIN});
    MR_NAME: ${MR_NAME}
    WP_URL: ${WP_URL}
  labels:
    - "traefik.enable=true"
    - "traefik.docker.network=traefik_wordpress_backend"
    - "traefik.http.routers.${MR_NAME}-wordpress.rule=PathPrefix(`${WP_PATH_PREFIX}`)"
    - "traefik.http.routers.${MR_NAME}-wordpress.entrypoints=web"
    - "traefik.http.routers.${MR_NAME}-wordpress.priority=50"
    - "traefik.http.routers.${MR_NAME}-wordpress.service=${MR_NAME}-wordpress"
    - "traefik.http.services.${MR_NAME}-wordpress.loadbalancer.server.port=80"
    - "traefik.http.middlewares.${MR_NAME}-stripprefix.stripprefix.prefixes=${WP_PATH_PREFIX}"
    - "traefik.http.middlewares.${MR_NAME}-fix-host.headers.customrequestheaders.Host=${WP_HOST}"
    - "traefik.http.middlewares.${MR_NAME}-fix-host.headers.customrequestheaders.X-Forwarded-Host=${WP_HOST}"
    - "traefik.http.middlewares.${MR_NAME}-fix-host.headers.customrequestheaders.X-Forwarded-Proto=http"
    - "traefik.http.middlewares.${MR_NAME}-fix-host.headers.customrequestheaders.X-Forwarded-Prefix=${WP_PATH_PREFIX}"
    - "traefik.http.routers.${MR_NAME}-wordpress.middlewares=${MR_NAME}-stripprefix@docker,${MR_NAME}-fix-host@docker"
  volumes:
    - wp_data:/var/www/html
  healthcheck:
    test: ["CMD", "curl", "-f", "http://localhost"]
    interval: 30s
    timeout: 10s
    retries: 5
    start_period: 60s

My Questions

  • Is there a recommended way to configure Traefik + WordPress for path-based multi-instance deployments (not subdomains)?

  • Should I be using StripPrefix, X-Forwarded-Prefix, or a different approach to make WordPress respect the path?

  • Are there any known best practices for handling wp-admin and wp-login.php behind Traefik when WordPress lives under a path prefix?

  • Do I need additional X-Forwarded-* headers (like X-Forwarded-Port) to avoid redirect loops?

Any guidance or working examples would be very helpful!

2

WordPress is very distinct about it's path: it insists on the path that is configured in the database, usually during initial setup, and it will continuously redirect to that path.

The usual solution is to update the path in the database to the new correct one, AFAIK it's in two places within the database.