# Routing inside Docker Swarm using Worker Hostname

**URL:** <https://community.traefik.io/t/routing-inside-docker-swarm-using-worker-hostname/17292>\
**Category:** Traefik v2\
**Tags:** docker, docker-swarm\
**Created:** [January 26, 2023, 4:22pm UTC](https://community.traefik.io/t/routing-inside-docker-swarm-using-worker-hostname/17292 "2023-01-26T16:22:11Z")\
**Posts on this page:** 5\
**Page:** 1

<div class="post-metadata">

**Author:** ![devmax](https://avatars.discourse-cdn.com/v4/letter/d/a8b319/32.png) [@devmax](https://community.traefik.io/u/devmax)\
**Post date:** [January 26, 2023, 4:22pm UTC](https://community.traefik.io/t/routing-inside-docker-swarm-using-worker-hostname/17292/1 "2023-01-26T16:22:11Z")

</div>

Hey,  
i have a am trying to scale a Large application. My Problem is, that I don't know how to configure Traefik the way I need to.  
In my Special Usecase I need scale 3 Docker container to over 100 Nodes. I can put a configuration Files on each Docker Worker.  
I want, that the Subdomain of the Containers on every Node is based on a configuration File / Environment.  
A example dockerfile can look like this\_

````auto
version: "3"
services:
  agent65:
    image: containous/whoami
    networks:
      - proxy
    deploy:
      mode: global
      labels:
        - "traefik.enable=true"
        - "traefik.http.routers.myapp.service=myapp_service"
        - "traefik.http.services.myapp_service.loadbalancer.server.port=80"
        - "traefik.http.routers.myapp.rule=Host(`{{ node_name }}.example.com`)"
        - "traefik.http.routers.myapp.tls=true"
        - "traefik.http.routers.myapp.tls.certresolver=lets-encrypt"
networks:
  proxy:
    driver: overlay
    external: true```
The Problem right now is, that I have no idea how to configure the {{ node_name }} part. I also don't know if it is possible.
I'm using docker-swarm, because the Server are not in the Internet. It's a closed Network.
In Theory I could write a script to automatically generate a Hughe docker-compose. But I want to avoid that. Any ideas?
````

---

<div class="post-metadata">

**Author:** ![bluepuma77](https://avatars.discourse-cdn.com/v4/letter/b/a9adbd/32.png) [@bluepuma77](https://community.traefik.io/u/bluepuma77)\
**Post date:** [January 27, 2023, 3:04pm UTC](https://community.traefik.io/t/routing-inside-docker-swarm-using-worker-hostname/17292/2 "2023-01-27T15:04:46Z")

</div>

We use [this notation](https://docs.docker.com/engine/reference/commandline/service_create/#create-services-using-templates) with `stack deploy` to set the container hostname automatically:

```auto
# docker-compose.yml
version: '3.9'

services:
  traefik:
    image: traefik:v2.9.6
    command: --configFile=/traefik.yml
    hostname: '{{.Node.Hostname}}'

```

This should probably work with `deploy mode:global` (with constraints) to have node\_name in a label. If you want your 3 containers on the same node to connect, you can maybe use an env var like `DB=db-{{.Node.Hostname}}.example.com` to reference each other.

---

<div class="post-metadata">

**Author:** ![devmax](https://avatars.discourse-cdn.com/v4/letter/d/a8b319/32.png) [@devmax](https://community.traefik.io/u/devmax)\
**Post date:** [January 28, 2023, 11:47am UTC](https://community.traefik.io/t/routing-inside-docker-swarm-using-worker-hostname/17292/3 "2023-01-28T11:47:15Z")

</div>

How do you handle the SSL Certificate? As soon as I do your solution, I get the following exception:

```auto
time="2023-01-27T17:04:52Z" level=info msg="Configuration loaded from file: /traefik.toml"
time="2023-01-28T11:42:24Z" level=error msg="Error while adding route for host: invalid value for \"HostSNI\" matcher, \"{{.node.hostname}}.example.com\" is not a valid hostname"
time="2023-01-28T11:42:24Z" level=error msg="Error while adding route for host: invalid value for \"HostSNI\" matcher, \"{{.node.hostname}}.example.com\" is not a valid hostname"
time="2023-01-28T11:42:25Z" level=error msg="Unable to obtain ACME certificate for domains \"{{.node.hostname}}.example.com\": unable to generate a certificate for the domains [{{.node.hostname}}.example.com]: acme: error: 400 :: POST :: https://acme-v02.api.letsencrypt.org/acme/new-order :: urn:ietf:params:acme:error:rejectedIdentifier :: Error creating new order :: Cannot issue for \"{{.node.hostname}}.example.com\": Domain name contains an invalid character" providerName=lets-encrypt.acme routerName=myapp@docker rule="Host(`{{.Node.Hostname}}.example.com`)" ACME CA="https://acme-v02.api.letsencrypt.org/directory"
time="2023-01-28T11:43:24Z" level=error msg="Error while adding route for host: invalid value for \"HostSNI\" matcher, \"{{.node.hostname}}.example.com\" is not a valid hostname"
time="2023-01-28T11:43:24Z" level=error msg="Error while adding route for host: invalid value for \"HostSNI\" matcher, \"{{.node.hostname}}.example.com\" is not a valid hostname"
time="2023-01-28T11:43:24Z" level=error msg="Unable to obtain ACME certificate for domains \"{{.node.hostname}}.example.com\": unable to generate a certificate for the domains [{{.node.hostname}}.example.com]: acme: error: 400 :: POST :: https://acme-v02.api.letsencrypt.org/acme/new-order :: urn:ietf:params:acme:error:rejectedIdentifier :: Error creating new order :: Cannot issue for \"{{.node.hostname}}.example.com\": Domain name contains an invalid character" ACME CA="https://acme-v02.api.letsencrypt.org/directory" providerName=lets-encrypt.acme routerName=myapp@docker rule="Host(`{{.Node.Hostname}}.example.com`)"

Using the following configuration:

version: "3"
services:
  agent65:
    image: containous/whoami
    networks:
      - proxy
    deploy:
      mode: global
      placement:
        constraints: [node.hostname == test-server-1]
      labels:
          - "traefik.enable=true"
          - "traefik.http.routers.myapp.service=myapp_service"
          - "traefik.http.services.myapp_service.loadbalancer.server.port=80"
          - "traefik.http.routers.myapp.rule=Host(`{{.Node.Hostname}}.example.com`)"
          - "traefik.http.routers.myapp.tls=true"
          - "traefik.http.routers.myapp.tls.certresolver=lets-encrypt"

networks:
  proxy:
    driver: overlay
    external: true

```

---

<div class="post-metadata">

**Author:** ![bluepuma77](https://avatars.discourse-cdn.com/v4/letter/b/a9adbd/32.png) [@bluepuma77](https://community.traefik.io/u/bluepuma77)\
**Post date:** [January 28, 2023, 3:39pm UTC](https://community.traefik.io/t/routing-inside-docker-swarm-using-worker-hostname/17292/4 "2023-01-28T15:39:24Z")

</div>

Your config has `Host()`, but the error is about `HostSNI()`. Seems the values have not been substituted, did you use `docker stack deploy`? Not sure if substitution works without it.

---

<div class="post-metadata">

**Author:** ![devmax](https://avatars.discourse-cdn.com/v4/letter/d/a8b319/32.png) [@devmax](https://community.traefik.io/u/devmax)\
**Post date:** [January 28, 2023, 3:59pm UTC](https://community.traefik.io/t/routing-inside-docker-swarm-using-worker-hostname/17292/5 "2023-01-28T15:59:54Z")

</div>

Yeah. The command was

```auto
docker stack deploy -c docker-compose.yml test

```