Function to shutdown nodejs/express http.Server gracefully

withShutdown.js

module.exports = withShutdown

// This may be unnessary with server.closeIdleConnections and server.closeAllConnections added in Node v18.2.0.

/**
 * Adds a shutdown function that destroys active connections
 * (such as keep-alive). Idle connections end immediately,
 * others are destroyed after all data is written.
 * 
 * @param {http.Server} server http.Server instance
 * @param {number} timeout ms to shutdown (defaulit is 1000)
 * @returns server with shutdown() function
 * @example
 *   const server = withShutdown(http.Server(app))
 *   process.on('SIGINT', ()=>server.shutdown())
 */
function withShutdown(server, timeout=1000) {
  server.socketIdleTimeout = timeout
  const active = []

  server.on('connection', (c)=>{
    const i = active.length
    active.push(c)
    c.on('close', ()=>active.splice(i, 1))
  })

  server.shutdown = function(cb) {
    server.close(cb)
    active.forEach(c=>c.destroySoon())
  }

  return server
}