Redirect to external URL, field not found, servers

Traefik Traefik v3 (latest)
, ,
1

Hello everyone, I am trying to have a redirect for google's tag manager first party setup, and I have this in my file provider

But I keep getting this error

{"level":"error","providerName":"swarm","container":"marketing-fps-forward-gxyn58z0g12pkfo6jrh0pkb14","error":"field not found, node: servers","time":"2025-01-11T20:50:43Z","caller":"github.com/traefik/traefik/v3/pkg/provider/docker/config.go:46"}

file provider

http:
  routers:
    fps-forward-router:
      rule: "Host(`example.com`) && PathPrefix(`/whatever`)"
      priority: 100
      tls:
        certResolver: letsencrypt
      entryPoints:
        - websecure
      middlewares:
        - fps-forward-redirect
      service: fps-forward-dummy

  services:
    # A "dummy" service so that our router can reference *some* service;
    fps-forward-dummy:
      loadBalancer:
        servers:
          - url: "http://0.0.0.0"

  middlewares:
    fps-forward-redirect:
      redirectRegex:
        # Regex captures the entire path (/whatever...) after the domain
        regex: "^https?://example.com(/whatever.*)"
        # Replacement sends everything to https://G-xxxx.fps.goog, preserving subpaths & query
        replacement: "https://x.fps.goog$1"
        permanent: true

This option is listed in the docs, what I am I missing?

Running traefik:v3.2.2

Trying to achieve the steps specified here Set up First-party mode  |  Google Tag Manager - First-party mode  |  Google for Developers

Edit: Moved to another solution not using the servers field, but I would still like to know what was happening so I can not make the same mistake in the future

2

The error comes from providers.swarm, so it’s probably about labels, not about the dynamic config file you shared.

Using a redirect seems very wrong when using Google first party stuff. It will tell the client to go fetch a Google page, which you probably want to avoid with the setup in the first place.

Chatbot answers can be very wrong sometimes.

3

This is in their guide

  1. Add an origin or backend that points to G-12345.fps.goog.
  2. Override the Host header to be equal to G-12345.fps.goog. Allow all cookies and query strings to be forwarded.
  3. Add a path rule for /metrics/* to route traffic to First-party mode.
  4. Configure the reserved path to have higher priority than the default rule.

Is there a more appropriate approach than a redirect? Maybe a dummy service that points to this URL? I did try that but it seems that swarm provider has issues with that, or I just misconfigured something

4

A redirect sends a redirect response to the client. Instead you should use regular Traefik proxy/forward via router and service with the target URL.

5

EDIT: the experimental version of traefik added the support for loadbalancer.server.url :smile:

It seems that docker swarm does not support the servers option?

I cannot really find anything about it in the docs

network_traefik.1.e6wjsmnf4hzl@manager-1    | {"level":"error","providerName":"swarm","container":"marketing-landing-yisytf7vr38x9nl07pgc5pvbu","error":"field not found, node: servers","time":"2025-01-13T06:56:55Z"}
network_traefik.1.e6wjsmnf4hzl@manager-1    | {"level":"error","providerName":"swarm","container":"marketing-landing-yisytf7vr38x9nl07pgc5pvbu","error":"field not found, node: servers","time":"2025-01-13T06:57:10Z"}
network_traefik.1.e6wjsmnf4hzl@manager-1    | {"level":"error","providerName":"swarm","container":"marketing-landing-yisytf7vr38x9nl07pgc5pvbu","error":"field not found, node: servers","time":"2025-01-13T06:57:25Z"}
network_traefik.1.e6wjsmnf4hzl@manager-1    | {"level":"error","providerName":"swarm","container":"marketing-landing-yisytf7vr38x9nl07pgc5pvbu","error":"field not found, node: servers","time":"2025-01-13T06:57:40Z"}
network_traefik.1.e6wjsmnf4hzl@manager-1    | {"level":"error","providerName":"swarm","container":"marketing-landing-yisytf7vr38x9nl07pgc5pvbu","error":"field not found, node: servers","time":"2025-01-13T06:57:55Z"}

        - "traefik.http.routers.fps-forward-router.rule=Host(`$VIRTUAL_HOST`) && PathPrefix(`/matrix`)"
        - "traefik.http.routers.fps-forward-router.priority=100"
        - "traefik.http.routers.fps-forward-router.entryPoints=websecure"
        - "traefik.http.routers.fps-forward-router.tls.certresolver=letsencrypt"

        - "traefik.http.routers.fps-forward-router.service=fps-forward-service"

        - "traefik.http.routers.fps-forward-router.middlewares=fps-forward-header"

        - "traefik.http.middlewares.fps-forward-header.headers.customrequestheaders.Host=$GOOGLE_TAG_ID.fps.goog"

        - "traefik.http.services.fps-forward-service.loadBalancer.servers.0.address=https://$GOOGLE_TAG_ID.fps.goog"
        - "traefik.http.services.fps-forward-service.loadBalancer.servers.0.tls=true"
        - "traefik.http.services.fps-forward-service.loadBalancer.passHostHeader=true"
6

The current doc (at this point v3.3) does not enable url on labels, only in file:

http:
  services:
    my-service:
      loadBalancer:
        servers:
          - url: "http://private-ip-server-1/"

Also experimental doc does not include it in labels.

Also docker reference experimental does not include it:

  - "traefik.http.services.service02.loadbalancer.server.port=foobar"
  - "traefik.http.services.service02.loadbalancer.server.preservepath=true"
  - "traefik.http.services.service02.loadbalancer.server.scheme=foobar"
  - "traefik.http.services.service02.loadbalancer.server.url=foobar"
  - "traefik.http.services.service02.loadbalancer.server.weight=42"

But in master branch providers.docker there is such a label (code):

"traefik.http.services.Service1.LoadBalancer.server.url": "http://1.2.3.4:5678"

And the issue has been closed now. Latest release v3.3.1 is older than the pull request, so we hopefully get it in the next release :clap: