使用线程的NodeJS .fork（）

Question

I'm needing to run Node servers for the development of several independent projects on a single box.

With Nginx in front routing based on virtual hosts, running 15+ node instances working separately isn't normally much of a problem. The catch is that just starting node that many times eats all my RAM with the overhead of just the internal libraries.

So does there exist a solution for this, allowing me to run several largely-independent Node servers while sharing the core libraries? Here are what I've considered:

• Threads instead of processes—there would exist a master control process that would be able to create a new thread for each instance. I know Node is built to not require threads, but is there a way to utilize them in order to save memory?
• Some library or addition to Node allowing me to do the above.
• Shared core memory between processes—is this a possibility for Node?
• Just require () ing in each server onto the same Node instance—I can't think how killing or reloading those servers could work. Is there a way to unrequire and restart an external module? This method could be ideal by allowing other libraries (Socket.IO for example) to be shared.

Anyway, this is probably an edge case, so I'm not surprised that a solution isn't obvious.

Does anyone know of a way to implement this?

Answer 1

The existing thread libraries limit your access to I/O pretty severely and are intended for you to run your own CPU-bound Javascript code, not serve out data. Shared core is certainly possible , but also a bit of a pain. I think your last option is the most viable. You can put together a virtualization system for node pretty easily.

Here are a couple standalone Express apps.

app-one.js:

var app = require('express')();

app.get('/', function (req, res) {
  res.send('This is app one.');
});

app.listen(3000);

app-two.js:

var app = require('express')();

app.get('/', function (req, res) {
  res.send('This is app two.');
});

app.listen(3001);

Change those by replacing the listen lines with assignments to the module:

app-one-virtual.js:

var app = require('express')();

app.get('/', function (req, res) {
  res.send('This is app one.');
});

module.exports = app;

app-two-virtual.js:

var app = require('express')();

app.get('/', function (req, res) {
  res.send('This is app two.');
});

module.exports = app;

Then write a master app that requires each of those and delegates requests to them based on the incoming host header:

app-master.js:

var http = require('http');
var appOne = require('./app-one-virtual');
var appTwo = require('./app-two-virtual');

http.createServer(function (req, res) {
  if (req.headers.host === 'one.example.com:3000') {
    return appOne(req, res)
  }
  if (req.headers.host === 'two.example.com:3000') {
    return appTwo(req, res)
  }
  res.writeHead(404)
  res.end('Site not found.')
}).listen(3000);

Now just node app-master.js and you're set. Repeat for as many servers as you like.