Closeable http server

closeable_http_server.ts

import * as http from 'http'
import * as _ from 'lodash'


//! In the standard implementation of http server, calling close is not guaranteed to close the
//! server.  Any idle connections being kept alive by clients will stay open until their timeout
//! is reached.  This is problematic for gracefully shutting down a process with an http server.
//! This function will create an http server that tracks the open connections.  On close, idle
//! connections are closed and any newly idled connection is immediately closed as well.  When there
//! are no more connections on the server, the 'empty' event is raised.
export function createCloseableHttpServer(
  requestListener?: (request: http.IncomingMessage, response: http.ServerResponse) => void
) {
  let nextId = 1;
  let active = true;
  let connections:any = {};

  // create the server
  let httpServer = http.createServer(requestListener);
  let origClose = httpServer.close;
  httpServer.close = close;
  httpServer.on('connection',onConnection);
  httpServer.on('request',onRequest);
  return httpServer;


  // ---- functions ----
  function onConnection(conn:any) {
    if ( !conn.$$id ) {
      conn.$$id = nextId++;
      conn.$$idle = true;
      connections[conn.$$id] = conn;
      conn.on('close',() => {
        delete connections[conn.$$id]
        emitOnEmpty();
      });
    }
    return conn;
  }

  function onRequest(req:http.IncomingMessage, res:http.ServerResponse) {

    // mark the connection as not idle
    let conn = onConnection(req.socket);
    conn.$$idle = false;

    // upon completion, mark the connection as idle
    res.on('finish',() => {
      conn.$$idle = true;
      destroy(conn);
    });
  }

  function close(cb?:any) {
    let rval = origClose.apply(httpServer,[cb]);
    if ( active ) {
      active = false;
      _.each(connections,(conn:any) => destroy(conn));
      emitOnEmpty();
    }
    return rval;
  };

  function destroy(conn:any) {
    if ( conn.$$idle && !active ) {
      conn.destroy();
    }
  }

  function emitOnEmpty() {
    if ( !active ) {
      if ( _.isEmpty(connections) ) {
        httpServer.emit('empty');
      }
    }
  }
}