Super simple docker-compose automatic tcp load balancer using nginx and docker-gen

docker-compose.yml

version: "3"
services:
  whoami: # the service(s) you want to load balance
    image: jwilder/whoami # this is an example placeholder (keep in mind that browsers keep connections open)
    labels:
      publish: "8000" # which port of this server to publish to the load balancer

  nginx:
    image: nginx
    container_name: lb_nginx_frontend
    volumes:
      - nginx-config:/etc/nginx:ro
    ports:
      - 80:80 # nginx listens on port 80 by default -- can be changed in nginx.tmpl

  docker-gen:
    image: jwilder/docker-gen
    volumes:
      - /var/run/docker.sock:/tmp/docker.sock:ro
      - nginx-config:/etc/nginx
      - ./nginx.tmpl:/etc/docker-gen/templates/nginx.tmpl

    command: -notify-sighup lb_nginx_frontend -watch /etc/docker-gen/templates/nginx.tmpl /etc/nginx/nginx.conf


volumes:
  nginx-config:

nginx.tmpl

user  nginx;
worker_processes  1;

error_log  /var/log/nginx/error.log warn;
pid        /var/run/nginx.pid;


events {
  worker_connections  1024;
}

{{ $backends := whereLabelExists $ "publish" }}
{{ $backendCount := len $backends }}

stream {
  {{ if ne $backendCount 0 }}
    upstream backend {
      {{ range $index, $backend := $backends }}
        # {{ $backend.Name }}
        server  {{ $backend.Name }}:{{ $backend.Labels.publish }};
      {{ end }}
    }
  {{ end }}

  {{ if ne $backendCount 0 }}
    server {
      listen  80;
      proxy_pass  backend;
    }
  {{ end }}
}