how to set proxy by request hostname with http-proxy-middleware and express?

Question

I want to configure proxy with http-proxy-middleware and express . The rule is a mapping of hostname, exmaple:

http://123.com   >>  http://localhost:3000/123
http://456.com   >>  http://localhost:3000/abc

I have tried like this:

import express from 'express';
import http from 'http';
import proxy from 'http-proxy-middleware';

const app = express();

app.use( async function (req, res) {  
  let direction = 'http://localhost:3000';
  console.log('hostname: ', req.hostname);
  console.log('originalUrl: ', req.originalUrl);
  if (req.hostname == '123.com') {
    direction = `http://localhost:3000/123${req.originalUrl}`;
  }
  if (req.hostname == '456.com') {
    direction = `http://localhost:3000/abc${req.originalUrl}`;
  }

  return await proxy({ target: direction, changeOrigin: false })
});

const server = http.createServer(app);
app.set('port', '127.0.0.1');
server.listen(9999, '0.0.0.0');

but it doesn't work.

Answer 1

There's a couple of things you need to consider:

• The http-proxy-middleware module does not return a promise, instead it returns an express middleware.
• You can use a custom filter to decide whether or not to proxy the request.
• You need to add the pathRewrite options in order to rewrite the url according to the current hostname.
• Another option would be to use the router option. See the relevant documentation.

I wrote a quick express app to test this (note that i overwrote my hosts file with localwebapp and localwebapp2 pointing to 127.0.0.1) and it seems to work fine:

const express = require('express')
const proxy = require('http-proxy-middleware')

const app = express();
const filter = (pathname, req) => {
    if (req.hostname == 'localwebapp' || req.hostname == 'localwebapp2') {
        return true;
    }
    return false;
};

app.get('/123*', (req, res) => {
    res.send(`matched 123* route: ${req.path}`);
})

app.get('/abc*', (req, res) => {
    res.send(`matched abc* route: ${req.path}`);
})

app.get('/test', (req, res) => {
    res.send("matched non proxied route '/test'");
})

const apiProxy = proxy(filter, {
    target: 'http://localhost:3000',
    logLevel: 'debug',
    changeOrigin: true,
    pathRewrite: function (path, req) {
        if (req.hostname == 'localwebapp') {
            return `/123${req.originalUrl}`;
        }
        if (req.hostname == 'localwebapp2') {
            return `/abc${req.originalUrl}`;
        }
        return path;
    }
})
app.use(apiProxy)
app.listen(3000);