unpkg/server.js

const http = require('http')
const throng = require('throng')
const createApp = require('./server/createApp')

const port = parseInt(process.env.PORT, 10) || 5000

throng({
  workers: process.env.WEB_CONCURRENCY || 1,
  lifetime: Infinity,
  grace: 25000,
  start: function (id) {
    const server = http.createServer(createApp())

    // Heroku dynos automatically timeout after 30s. Set our
    // own timeout here to force sockets to close before that.
    // https://devcenter.heroku.com/articles/request-timeout
    server.setTimeout(25000, function (socket) {
      const message = `Timeout of 25 seconds exceeded`

      socket.end([
        `HTTP/1.1 503 Service Unavailable`,
        `Date: ${(new Date).toGMTString()}`,
        `Content-Type: text/plain`,
        `Content-Length: ${Buffer.byteLength(message)}`,
        `Connection: close`,
        ``,
        message
      ].join(`\r\n`))
    })

    server.listen(port, function () {
      console.log('Server #%s listening on port %s, Ctrl+C to stop', id, port)
    })
  }
})