traefik / ProxyPass: using stripprefix, I get a 404 for sub queries

userRlNl1 0
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I try to configure my registry service to intercep host+path https://my-dns.org/registry and redirect to the service http://registry-ui

here is configured my compose :

...

  registry-ui:
    image: joxit/docker-registry-ui:latest
    container_name: registry-ui
    restart: unless-stopped
    environment:
      - REGISTRY_TITLE=My registry
      - NGINX_PROXY_PASS_URL=http://registry:5000
      - SINGLE_REGISTRY=true
      - DELETE_IMAGES=true
    depends_on:
      - registry
    labels:
      - "traefik.enable=true"
      - "traefik.http.routers.registry-ui.entrypoints=https"
      - "traefik.http.routers.registry-ui.rule=Host(`my-dns.org`) && PathPrefix(`/registry`)"
      - "traefik.http.routers.registry-ui.middlewares=test-stripprefix"
      - "traefik.http.routers.registry-ui.tls.certresolver=myresolver"
      - "traefik.http.middlewares.test-stripprefix.stripprefix.prefixes=/registry"
      - "traefik.http.middlewares.test-stripprefix.stripprefix.forceSlash=false"
      - "traefik.http.services.registry-ui.loadbalancer.server.port=80"
...

As a result, the index page works fine, but css, js and favicon are lost because the requests look like :

  • https://my-dns.org/docker-registry-ui.css instead of
  • https://my-dns.org/registry/docker-registry-ui.css

Any idea on how to fix that ?

traefik middleware configuration docker
1 Answers

This will only work as long as the app you are trying to start does NOT set a custom html <base> to something hardcoded like root /.

If this is not the case you might be in luck!

Your links to sub resources are probably defined relative something like this.

<link rel="stylesheet" type="text/css" href="docker-registry-ui.css" />

So when you enter into the browser https://my-dns.org/registry your page opens but all links and subsequently css, js is completely broken because the base directory the relative links are based on is still the directory https://my-dns.org/ because you did not enter a subdirectory. The /registry is handled like it is a file and is ignored for relative links.

  • URL: https://my-dns.org/registry
  • Base: https://my-dns.org/
  • Relative Link: docker-registry-ui.css
  • Result: https://my-dns.org/docker-registry-ui.css ⇒ HTTP 404 not found

For your path prefix to work you need to enter a trailing slash / to access your service. Then the relative links will work as expected.

  • URL: https://my-dns.org/registry/
  • Base: https://my-dns.org/registry/
  • Relative Link: docker-registry-ui.css
  • Result: https://my-dns.org/registry/docker-registry-ui.css ⇒ Link working as expected

Try to access your service with https://my-dns.org/registry/ (trailing slash) for your links to work as expected.

If you really must use the link without the trailing slash / to work, you need a path rewrite step to add the trailing slash or alternatively a redirection from https://my-dns.org/registry to https://my-dns.org/registry/.

Adjust your configuration to add add the trailing slash:

    labels:
      - "traefik.enable=true"
      - "traefik.http.routers.registry-ui.entrypoints=https"
      - "traefik.http.routers.registry-ui.rule=Host(`my-dns.org`) && PathPrefix(`/registry/`)"
      - "traefik.http.routers.registry-ui.middlewares=test-stripprefix"
      - "traefik.http.routers.registry-ui.tls.certresolver=myresolver"
      - "traefik.http.middlewares.test-stripprefix.stripprefix.prefixes=/registry/"
      - "traefik.http.services.registry-ui.loadbalancer.server.port=80"
Leonhard Bauer0
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