How to reverse proxy client POST & PUT requests using node-http-proxy

Question

I'm trying to use the node-http-proxy as a reverse proxy, but I can't seem to get POST and PUT requests to work. The file server1.js is the reverse proxy (at least for requests with the url "/forward-this") and server2.js is the server that receives the proxied requests. Please explain what I'm doing incorrectly.

Here's the code for server1.js:

// File: server1.js
//

var http = require('http');
var httpProxy = require('http-proxy');

httpProxy.createServer(function (req, res, proxy) {
    if (req.method == 'POST' || req.method == 'PUT') {
        req.body = '';

        req.addListener('data', function(chunk) {
            req.body += chunk;
        });

        req.addListener('end', function() {
            processRequest(req, res, proxy);
        });
    } else {
        processRequest(req, res, proxy);
    }

}).listen(8080);

function processRequest(req, res, proxy) {

    if (req.url == '/forward-this') {
        console.log(req.method + ": " + req.url + "=> I'm going to forward this.");

        proxy.proxyRequest(req, res, {
            host: 'localhost',
            port: 8855
        });
    } else {
        console.log(req.method + ": " + req.url + "=> I'm handling this.");

        res.writeHead(200, { "Content-Type": "text/plain" });
        res.write("Server #1 responding to " + req.method + ": " + req.url + "\n");
        res.end();
    }
}

And here's the code for server2.js:

// File: server2.js
// 

var http = require('http');

http.createServer(function (req, res, proxy) {
    if (req.method == 'POST' || req.method == 'PUT') {
        req.body = '';

        req.addListener('data', function(chunk) {
            req.body += chunk;
        });

        req.addListener('end', function() {
            processRequest(req, res);
        });
    } else {
        processRequest(req, res);
    }

}).listen(8855);

function processRequest(req, res) {
    console.log(req.method + ": " + req.url + "=> I'm handling this.");

    res.writeHead(200, { 'Content-Type': 'text/plain' });
    res.write("Server #2 responding to " + req.method + ': url=' + req.url + '\n');
    res.end();
}

Answer 1

http-proxy depends on the data and end events for POST / PUT requests. The latency between the time that server1 receives the request and when it is proxied means that http-proxy misses those events entirely. You have two options here to get this to work correctly - you can buffer the request or you can use a routing proxy instead. The routing proxy seems the most appropriate here since you only need to proxy a subset of requests. Here's the revised server1.js:

// File: server1.js
//

var http = require('http');
var httpProxy = require('http-proxy');
var proxy = new httpProxy.RoutingProxy();

http.createServer(function (req, res) {
    if (req.url == '/forward-this') {
        return proxy.proxyRequest(req, res, {
            host: 'localhost',
            port: 8855
        });
    }

    if (req.method == 'POST' || req.method == 'PUT') {
        req.body = '';

        req.addListener('data', function(chunk) {
            req.body += chunk;
        });

        req.addListener('end', function() {
            processRequest(req, res);
        });
    } else {
        processRequest(req, res);
    }

}).listen(8080);

function processRequest(req, res) {
    console.log(req.method + ": " + req.url + "=> I'm handling this.");

    res.writeHead(200, { "Content-Type": "text/plain" });
    res.write("Server #1 responding to " + req.method + ": " + req.url + "\n");
    res.end();
}

Answer 2

In addition to @squamos

How to write a node express app that serves most local files, but reroutes some to another domain?

var proxy = new httpProxy.RoutingProxy();

"Above code is working for http-proxy ~0.10.x. Since then lot of things had changed in library. Below you can find example for new version (at time of writing ~1.0.2)"

var proxy = httpProxy.createProxyServer({});

Answer 3

Here is my solution for proxying POST requests. This isn't the most ideal solution, but it works and is easy to understand.

var request = require('request');

var http = require('http'),
    httpProxy = require('http-proxy'),
    proxy = httpProxy.createProxyServer({});

http.createServer(function(req, res) {
    if (req.method == 'POST') {
        request.post('http://localhost:10500/MyPostRoute',
                     {form: {}},
                     function(err, response, body) {
                         if (! err && res.statusCode == 200) {
                            // Notice I use "res" not "response" for returning response
                            res.writeHead(200, {'Content-Type': "application/json"});
                            res.end(body);
                         }
                         else {
                             res.writeHead(404, {'Content-Type': "application/json"});
                             res.end(JSON.stringify({'Error': err}));
                         }
                     });
    }
    else  if (req.method == 'GET') {
        proxy.web(req, res, { target: 'http://localhost/9000' }, function(err) {
            console.log(err) 
        });
    }

The ports 10500 and 9000 are arbitrary and in my code I dynamically assign them based on the services I host. This doesn't deal with PUT and it might be less efficient because I am creating another response instead of manipulating the current one.