Routing inside Docker Swarm using Worker Hostname

Traefik Traefik v2
,
1

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_

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?
2

We use this notation with stack deploy to set the container hostname automatically:

# 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.

3

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

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
4

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.

5

Yeah. The command was

docker stack deploy -c docker-compose.yml test