Routing to Different SQL Server Instances Running through Docker on Default Port

Question

I can use Traefik for web sites since they use headers when they are connecting. But I want to have multiple different instances of SQL Server running through docker which will be externally available (outside the docker host, potentially outside the local network)

So, is there anything which allows connecting to different sql server instances running on the same docker instance WITHOUT having to give them different ports or external ip addresses such that someone could access

sql01.docker.local,1433 AND sql02.docker.local,1433 from SQL Tools.

Start Additional Question

Since there has been no replies perhaps there is a way to have different instances like: sql.docker.local\instance1 and sql.docker.local\instance2 though I imagine that may also not be possible

End Additional Question

This is an example of the docker-compose file I was trying to use (before I realised that queries to sql server don't send through a host header - or am I wrong about that?)

version: '2.1'
services:
  traefik:
    container_name: traefik
    image: stefanscherer/traefik-windows
    command: --docker.endpoint=tcp://172.28.80.1:2375 --logLevel=DEBUG
    ports:
      - "8080:8080"
      - "80:80"
      - "1433:1433"
    volumes:
      - ./runtest:C:/etc/traefik
      - C:/Users/mvukomanovic.admin/.docker:C:/etc/ssl
    networks:
      - default
    restart: unless-stopped
    labels:
      - "traefik.enable=false"

  whoami:
    image: stefanscherer/whoami
    labels:
      - "traefik.backend=whoami"
      - "traefik.frontend.entryPoints=http"
      - "traefik.port=8080"
      - "traefik.frontend.rule=Host:whoami.docker.local"
    networks:
      - default
    restart: unless-stopped


  sql01:
    image: microsoft/mssql-server-windows-developer
    environment:
      - ACCEPT_EULA=Y
    hostname: sql01
    domainname: sql01.local
    networks:
      - default
    restart: unless-stopped
    labels:
      - "traefik.frontend.rule=Host:sql01.docker.local,sql01,sql01.local"
      - "traefik.frontend.entryPoints=mssql"
      - "traefik.port=1433"
      - "traefik.frontend.port=1433"
    networks:
      - default
    restart: unless-stopped    
  sql02:
    image: microsoft/mssql-server-windows-developer
    environment:
      - ACCEPT_EULA=Y
    hostname: sql02
    domainname: sql02.local
    networks:
      - default
    restart: unless-stopped
    labels:
      - "traefik.frontend.rule=Host:sql02.docker.local,sql02,sql02.local"
      - "traefik.frontend.entryPoints=mssql"
      - "traefik.port=1433"
      - "traefik.frontend.port=1433"
    networks:
      - default
    restart: unless-stopped    

networks:
  default:
    external:
      name: nat

Answer 1

As mentionned earlier traefik is not the right solution since it's a HTTP only LoadBalancer.

I can think right now in 3 different ways to achieve what you want to do :

• Use a TCP Load Balancer like HAproxy
• Setup you server in Docker Swarm Mode (https://docs.docker.com/engine/swarm/), that will allow to bind the same port with a transparent routing between them
• Use a service discovery service like consul and SRV records that can abstracts ports number (this might be overkill for your needs and complex to setup)