nginx config for two ATCs with docker-compose

docker-compose-two-atcs.yml

version: '3'

services:
  db:
    image: postgres
    ports:
    - 6543:5432
    environment:
      POSTGRES_DB: concourse
      POSTGRES_USER: dev
      POSTGRES_PASSWORD: dev

  web1:
    build:
      context: .
      dockerfile: ${DOCKERFILE}
    image: concourse/concourse:local
    volumes:
    - .:/src
    command: web
    depends_on: [db]
    ports:
    - 8081:8080
    environment:
      CONCOURSE_POSTGRES_HOST: db
      CONCOURSE_POSTGRES_USER: dev
      CONCOURSE_POSTGRES_PASSWORD: dev
      CONCOURSE_POSTGRES_DATABASE: concourse
      CONCOURSE_EXTERNAL_URL: http://localhost:8080
      CONCOURSE_ADD_LOCAL_USER: test:test,guest:guest
      CONCOURSE_MAIN_TEAM_LOCAL_USER: test
      CONCOURSE_LOG_LEVEL: debug
  web2:
    build:
      context: .
      dockerfile: ${DOCKERFILE}
    image: concourse/concourse:local
    volumes:
    - .:/src
    command: web
    depends_on: [db]
    ports:
    - 8082:8080
    environment:
      CONCOURSE_POSTGRES_HOST: db
      CONCOURSE_POSTGRES_USER: dev
      CONCOURSE_POSTGRES_PASSWORD: dev
      CONCOURSE_POSTGRES_DATABASE: concourse
      CONCOURSE_EXTERNAL_URL: http://localhost:8080
      CONCOURSE_ADD_LOCAL_USER: test:test,guest:guest
      CONCOURSE_MAIN_TEAM_LOCAL_USER: test
      CONCOURSE_LOG_LEVEL: debug

  lb:
    image: nginx:latest
    volumes:
    - /tmp/n:/etc/nginx/nginx.conf
    depends_on: [web1, web2]
    ports:
      - 8080:8080

  worker:
    build:
      context: .
      dockerfile: ${DOCKERFILE}
    image: concourse/concourse:local
    command: worker
    privileged: true
    depends_on: [web1, web2]
    ports:
    - 7777:7777
    - 7788:7788
    environment:
      CONCOURSE_LOG_LEVEL: debug
      CONCOURSE_TSA_HOST: web1:2222,web2:2222
      CONCOURSE_EPHEMERAL: ${CONCOURSE_EPHEMERAL:-true}

      # avoid using loopbacks
      CONCOURSE_BAGGAGECLAIM_DRIVER: overlay

      # so we can reach Garden/Baggageclaim for debugging
      CONCOURSE_BIND_IP: 0.0.0.0
      CONCOURSE_BAGGAGECLAIM_BIND_IP: 0.0.0.0

nginx.conf

events { }
http {
  upstream localhost {
        server web1:8080;
        server web2:8080;
  }
  server {
    listen 8080;
    server_name localhost;
    location / {
       proxy_pass http://localhost;
       proxy_set_header Host $host;
    }
  }
}