Testing HAProxy backend DNS resolution

app.js

const http = require('http');
const os = require('os');

let num = 0;

setTimeout(() => {
  console.log(os.hostname(), num);
  process.exit(0);
}, 60000);

http.createServer(function (req, res) {
  num++;
  res.write('OK');
  res.end();
}).listen(8000);

docker-compose.yml

---
version: '2'
services:
  haproxy:
    image: haproxy
    ports:
      - '80:80'
    volumes:
      - './haproxy.cfg:/usr/local/etc/haproxy/haproxy.cfg'

  api:
    image: node
    command: node /app.js
    volumes:
      - './app.js:/app.js'

haproxy.cfg

resolvers docker
  nameserver default 127.0.0.11:53
  hold valid 1000ms

frontend proxy
  mode http
  bind 0.0.0.0:80 maxconn 10000
  option http-server-close
  option forwardfor
  timeout client 5000
  default_backend api

backend api
  mode http
  timeout connect 100
  timeout server 5000
  option httpchk GET /
  server-template api 5 api:8000 maxconn 10000 check inter 1000