Environment variable in a toml dynamic file

[BDIFluky]

Welcome!

• Yes, I've searched similar issues on GitHub and didn't find any.
• Yes, I've searched similar issues on the Traefik community forum and didn't find any.

What did you do?

I apologize in advance if I make any mistake creating this issue, this is my first one on github,I'll try to be concise.
I configured the dashboard and api routers using a dynamic file, setting a rule that uses an environmental variable (DOMAIN_NAME) as so:

[http]
  [http.routers]
    [http.routers.dashboard]
      middlewares = ["dashboard_redirect", "dashboard_stripprefix"]
      service = "dashboard@internal"
      rule = "Host(`traefik.{{env "DOMAIN_NAME"}}`) && PathPrefix(`/`)"
      priority = 1000
      
    [http.routers.api]
      service = "api@internal"
      rule = "Host(`traefik.{{env "DOMAIN_NAME"}}`) && PathPrefix(`/api`)"
      priority = 1001

   [http.middlewares]
    [http.middlewares.dashboard_redirect.redirectRegex]
      regex = "^(http:\\/\\/(\\[[\\w:.]+\\]|[\\w\\._-]+)(:\\d+)?)\\/$"
      replacement = "${1}/dashboard/"
      permanent = true

    [http.middlewares.dashboard_stripprefix.stripPrefix]
      prefixes = ["/dashboard/", "/dashboard"]

the issue is the accepted syntax is the one above which isn't the right syntax for a toml file, I think the quotes encapsulating DOMAIN_NAME should be escaped with a \

What did you see instead?

using escaped auotes triggers an error where traefik can't seem to accept the syntax, this is the error:

ERR github.com/traefik/traefik//v3/pkg/provider/file/file.go:150 > Error occurred during watcher callback error="/dynamic/api.toml: template: :6: unexpected \"\\\\\" in operand" providerName=file

but using the escaped quotes in the static file seems to work fine, for example this is my providers configuration in a toml static file:

[providers]  
  [providers.docker]
    exposedByDefault = false
    defaultRule = "Host(`{{ .ContainerName }}.{{env \"DOMAIN_NAME\"}}`)"

  [providers.file]
    directory = "/dynamic"
    watch = true

What version of Traefik are you using?

Version: 3.1.2
Codename: comte
Go version: go1.22.5
Built: 2024-08-06T13:37:51Z
OS/Arch: linux/amd64

What is your environment & configuration?

Platform: Debian 12.6.0
Container Manage: Podman

traefik.toml:

################################################################
# Global configuration
################################################################
[global]
  checkNewVersion = true
  sendAnonymousUsage = false


################################################################
# Entrypoints configuration
################################################################
[entryPoints]
  [entryPoints.web]
    address = ":80"
      [entryPoints.web.http]
        [entryPoints.web.http.redirections]
          [entryPoints.web.http.redirections.entryPoint]
            to = "websecure"
            scheme = "https"

  [entryPoints.websecure]
    address = ":443"
    asDefault = true
      [entryPoints.websecure.http]
        [entryPoints.websecure.http.tls]
          certResolver = "letsencrypt"


################################################################
# Traefik logs configuration
################################################################
[log]
  level = "DEBUG"


################################################################
# API and dashboard configuration
################################################################
[api]
  insecure = false
  dashboard = true

################################################################
# Ping configuration
################################################################
[ping]


################################################################
# Docker configuration backend
################################################################
[providers]  
  [providers.docker]
    exposedByDefault = false
    defaultRule = "Host(`{{ .ContainerName }}.{{env \"DOMAIN_NAME\"}}`)"

  [providers.file]
    directory = "/dynamic"
    watch = true

################################################################
# Let's Encrypt
################################################################
[certificatesresolvers.letsencrypt.acme]
  email = "fluky@bdi.brr"
  storage = "/letsencrypt/acme.json"
  preferredchain="ISRG Root X1"
  keytype="RSA4096"
  [certificatesResolvers.letsencrypt.acme.tlsChallenge]

dynamic file:

[http]
  [http.routers]
    [http.routers.dashboard]
      middlewares = ["dashboard_redirect", "dashboard_stripprefix"]
      service = "dashboard@internal"
      rule = "Host(`traefik.{{env "DOMAIN_NAME"}}`) && PathPrefix(`/`)"
      priority = 1000
      
    [http.routers.api]
      service = "api@internal"
      rule = "Host(`traefik.{{env "DOMAIN_NAME"}}`) && PathPrefix(`/api`)"
      priority = 1001

   [http.middlewares]
    [http.middlewares.dashboard_redirect.redirectRegex]
      regex = "^(http:\\/\\/(\\[[\\w:.]+\\]|[\\w\\._-]+)(:\\d+)?)\\/$"
      replacement = "${1}/dashboard/"
      permanent = true

    [http.middlewares.dashboard_stripprefix.stripPrefix]
      prefixes = ["/dashboard/", "/dashboard"]

compose.yml:

services:

  traefik:
    image: "docker.io/traefik:v3.1"
    container_name: "traefik"
    ports:
      - "8080:80"
      - "8443:443"
    env_file:
      -.traefik.env
    volumes:
      - "/run/user/%U/podman/podman.sock:/var/run/docker.sock:ro"
      - "/%h/letsencrypt:/letsencrypt"
      - "/%h/traefik/traefik.toml:/etc/traefik/traefik.toml"
      - "/%h/traefik/dynamic:/dynamic"
    healthcheck:
      test: ["CMD", "traefik", "healthcheck", "--ping"]
      interval: 10s
      timeout: 5s
      retries: 3
      start_period: 10s

  whoami:
    image: "docker.io/traefik/whoami"
    container_name: "whoami"
    labels:
      - "traefik.enable=true"

If applicable, please paste the log output in DEBUG level

No response

[rtribotte]

Hello @BDIFluky,

Thanks for your interest in Traefik,

It seems that your issue is related to a configuration issue that is not related directly to Traefik and the GitHub issue tracker is dedicated to bug and feature requests.

For help on your configuration, please join our Community Forum and reach out to us on the Traefik v3 section.

We will close this issue accordingly but feel free to re-open it if you think that we missed something.

[BDIFluky]

Hello,
thanks for your reply, the configuration I gave works, so I don't have a problem making it work, it's just I noticed that the go file (file.go line 150) accepts a wrong syntax for a toml file referencing an env variable using a go template (unless i'm mistaken).