http-party / node-http-proxy

A full-featured http proxy for node.js

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hanging POST requests

joeyAghion opened this issue · comments

I'm using express and trying to proxy certain requests to a different server, as follows (simplified):

var httpProxy = require('http-proxy');
var apiProxy = new httpProxy.RoutingProxy();
app.all('/api/*', function(req, res){
  apiProxy.proxyRequest(req, res, {host: '', port: 9000});

...but POST requests to my server appear to just hang, and never arrive at the target server.

I'm working on a stripped-down-but-working example of this but thought I'd ask first. Has anyone seen this behavior, or are there good examples of node-http-proxy coexisting with express?

I believe your issue may be solved by using the buffer method. A very good explanation can be found here.

@AvianFlu: Thanks for the buffer pointer, but this ended up being caused by express's body-parsing.

Instead of declaring the API route (for proxying) within express routes, I configured it as middleware and used it before express.bodyParser().

Some coffeescript of the solution:

httpProxy = require 'http-proxy'
routingProxy = new httpProxy.RoutingProxy()
apiProxy = (pattern, host, port) ->
  (req, res, next) ->
    if req.url.match(pattern)
      routingProxy.proxyRequest req, res, host: host, port: port

app.configure ->
  @set 'views', 'app/templates'
  # ...
  @use apiProxy /\/api\/.*/, 'localhost', 3000
  @use express.bodyParser()
  # ...

You're correct - express's body parsing turns the request stream into a regular object. The solution is either to buffer it, as I was suggesting, or to deal with the request before the parsing, as you ended up doing. Glad you figured it out!

I ran into this problem too .. http-proxy@0.8.0, express@2.5.8, connect@1.8.5.

In my case, it turns out that http-proxy's buffer doesn't play well with connect's bodyParser middleware. The buffer is adding listeners for the 'data' and 'end' events to the request object so that it can re-emit them later (on a call to proxyRequest, e.g.). The bodyParser middleware is also adding listeners for the 'data' and 'end' events to the request object but they are never removed. So when re-emitted by the buffer, they're picked up a second time by the bodyParser.

This can result in JSON parse errors and "Can't render headers after they are sent to the client" exceptions (and probably other errors).

For those having issues with this, I found that this information seemed a bit out of date or difficult to implement (too much so for me, at least), compared to using connect-restreamer. That approach is outlined in the middleware example for using the bodyParser:

So, How to solve this problem?

connect-restreamer worked for me. The last thing in my middle-ware is:


Then I have a can do the proxy request normally:

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

app.get('/proxy/', function (req, res) {
  routingProxy.proxyRequest(req, res, {
    host : host,
    port : port

Configuring the proxy as part of middleware before bodyParser (if this is an option for you) also worked for me.

I did not attempt the buffer solution.

Also, simply not using the bodyParser also works (for anyone's future reference).

This thread has helped me. Thanks everyone.

Helpful, Thanks!

For some reason, connect-restreamer didn't fix it for me.

If anyone wants yet another fix, I ended up just calling bodyParser manually. So the proxying worked since bodyParser is not in the middleware. The code looked like:

var connect = require('connect');
var bodyParser = connect.bodyParser();

..."/blah", function(req, res) {
    bodyParser(req, res, function() {
        // Now do something with req.body.thePostData


Man, you saved my life!

Thanks for that solution it works fine
Just configure the proxy as part of middleware before bodyParser

Restreamer works for me. I needed to leave bodyParser because my proxy was conditional upon the contents of the request body. Here is a working example authored by someone else:

The example from bodyDecoder pointed out by @gdw2 does not work for me. I get

    throw err;
Error: write after end
    at ClientRequest.OutgoingMessage.write (_http_outgoing.js:413:15)
    at IncomingMessage.ondata (_stream_readable.js:540:20)
    at IncomingMessage.emit (events.js:107:17)
    at /Code/project/lib/server.js:46:25
    at process._tickCallback (node.js:355:11)

Using connect-restreamer results in the request continuing to hang.

I am using express instead of connect.

var express = require('express'),
    bodyParser = require('body-parser'),
    httpProxy = require('http-proxy');

var proxy = httpProxy.createProxyServer({changeOrigin: true});
var restreamer = function (){
  return function (req, res, next) { //restreame
    process.nextTick(function () {
      if(req.body) {
        req.emit('data', req.body)

var app = express();

app.use(bodyParser.urlencoded({extended: false, type: 'application/x-www-form-urlencoded'}));

app.all("/api/*", function(req, res) {
    //modifying req.body here
    proxy.web(req, res, { target: 'http://urlToServer'});


This may related to this issue however.

@FoxxMD same behavior here

For those in the unfortunate position not being able to rearrange/remove the bodyparser middleware:
I've added the snippet from the example bodyDecode middleware right before I use proxy.web(...) and it just werkz


process.nextTick(function () {
if(req.body) {
   req.emit('data', JSON.stringify(req.body));
proxyServer.web( [...] );

Hope that helps. This was really frustrating.


restreamer didn't work for me.
Only way I was able to get it working with routing is like this: '/api/*', (req, res)->
  r = new http.IncomingMessage()
  r.httpVersion = req.httpVersion
  r.method = req.method
  r.headers = req.headers
  delete r.headers['accept-encoding']
  r.url = req.url
  r.socket = req.socket
  body = JSON.stringify(req.body)
  r.body = body
  size = Buffer.byteLength(body, 'utf8')
  r.headers['content-type'] = "application/json;charset=UTF-8"
  r.headers['content-length'] = size
  buffer = {}
  buffer.pipe = (dest)->
    process.nextTick ->
  proxy.web(r, res, {
    buffer: buffer
    target: "http://localhost:1600"
    proxyTimeout: 5000

@schumacher-m thanks for that for me

@schumacher-m BIG thanks for your tips. It works around the hang issue finally - after a whole day of debugging.

Thanks @schumacher-m . There's actually also an example in the repo itself that handles the same issue:

Thanks all - I went with OP's suggestion and moved the proxy route above the bodyParser middleware


I used all of the solution above, _but it's not worked anyway_.
So, I read the http-proxy source and request API, I found that's the question of request.
and http-proxy have no solution with the body parameters .
There is no need to use a middleware.

And this is my solution:

var proxy = httpProxy.createProxyServer();
proxy.on('proxyReq', function(proxyReq, req, res, options) {

var headers = {};
    var data = JSON.stringify(req.body);
    req.body = data;
    headers = { 
        "Content-Type": "application/json",
        "Content-Length": data.length
proxy.web(req, res, {
    target: url,

@vvpvvp,Can i modify/add req.newkey = 'a' and send it to the proxy

None of these solutions work with the latest version of express & http-proxy, any suggestions? Here is what my code looks like - I still get the hanging POST request issue. I am just trying to read the POST body before conditionally proxying the request.

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

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

app.use(restreamer());'/', function(req, res) {
 proxy.web(req, res, { target: URL });

EDIT: I am now getting a 'write after end' error which is odd because I am using restreamer.

@vvpvvp big thinks for your tips

@narciero I am also getting same error. Did you find any workaround for this ?


Putting this before using the express body parser worked for me! Thanks for the help guys.


I have done slightly similar yet different fix for this, without using any restreamer, take a look here

Idea is to not use the body-parser as middleware instead apply only to the matched routes in my local web server and hence don't bring in the body-parser at all in between proxy and the local web server

Comments, suggestions welcome

Here is my solution:

import { createServer as createHttpServer } from 'http'
import { createProxyServer } from 'node-http-proxy'

function parseBody(message) {
  const body = []

  return new Promise((resolve, reject) => {
    message.on('data', c => body.push(c))
    message.on('end', () => resolve(body))
    message.on('error', err => reject(err))

export default function createServer(proxyCfg, port) {
  const proxyServer = createProxyServer(proxyCfg)
    .on('proxyReq', onProxyReq)

  function onProxyReq(proxyReq, req, res) {
    if (req.body && req.body.length) {
      proxyReq.write(new Buffer(req.body[0]))
  createHttpServer(async (req, res) => {
    req.body = parseBody(req)
    if (!res.headersSent) {
      proxyServer.web(req, res)

The bodyDecoder-middleware.js example shows a similar implementation of this:

//restream parsed body before proxying
proxy.on('proxyReq', function(proxyReq, req, res, options) {
  if(req.body) {
    let bodyData = JSON.stringify(req.body);
    // incase if content-type is application/x-www-form-urlencoded -> we need to change to application/json
    proxyReq.setHeader('Content-Length', Buffer.byteLength(bodyData));
    // stream the content

Amazing, this issue is 5 years old...

For anyone who has this issue of POST requests timing out through the proxy because of the post body, the middleware solution linked above ( worked for me. However, it did have a 'gotcha' - the code looks for an exact match on the contentType header, which might not happen:

	proxy.on( 'proxyReq', ( proxyReq, req, res, options ) => {
		if ( !req.body || !Object.keys( req.body ).length ) {

		let contentType = proxyReq.getHeader( 'Content-Type' );
		let bodyData;

		if ( contentType.includes( 'application/json' ) ) {
			bodyData = JSON.stringify( req.body );

		if ( contentType.includes( 'application/x-www-form-urlencoded' ) ) {
			bodyData = queryString.stringify( req.body );

		if ( bodyData ) {
			proxyReq.setHeader( 'Content-Length', Buffer.byteLength( bodyData ) );
			proxyReq.write( bodyData );

Hope this helps someone who comes here (I should really put it on StackOverflow, shouldn't I?).

@vshih @kevteljeur thank you, I have tried this modified approach, that now is also in the examples, but for some reason it does not forward the body as json and I get an error. Asked on SF as well.

The error by middleware side was

[Tue Sep 25 2018 18:16:29 GMT+0200 (CEST)] trapped error code: message:Can't set headers after they are sent. stack:Error: Can't set headers after they are sent.
    at validateHeader (_http_outgoing.js:491:11)
    at ClientRequest.setHeader (_http_outgoing.js:498:3)
    at ProxyServer.<anonymous> (/webservice/lib/api.js:616:34)
    at ProxyServer.emit (/webservice/node_modules/eventemitter3/index.js:210:27)
    at ClientRequest.<anonymous> (/webservice/node_modules/http-proxy/lib/http-proxy/passes/web-incoming.js:132:27)
    at emitOne (events.js:121:20)
    at ClientRequest.emit (events.js:211:7)
    at tickOnSocket (_http_client.js:652:7)
    at onSocketNT (_http_client.js:668:5)
    at _combinedTickCallback (internal/process/next_tick.js:138:11)
    at process._tickDomainCallback (internal/process/next_tick.js:218:9):

The error on the backend (tornado) was Malformed HTTP message from Malformed HTTP headers: '\r\n0\r\n\r\n'

while I did the reastream like

//restream parsed body before proxying
                proxy.on('proxyReq', function (proxyReq, req, res, options) {
                    if (!req.body || !Object.keys(req.body).length) {
                    var contentType = proxyReq.getHeader('Content-Type');
                    var bodyData;

                    if (contentType === 'application/json') {
                        bodyData = JSON.stringify(req.body);

                    if (contentType === 'application/x-www-form-urlencoded') {
                        bodyData = queryString.stringify(req.body);

                    if (bodyData) {
                        console.log("------", bodyData);
                        proxyReq.setHeader('Content-Length', Buffer.byteLength(bodyData));
                proxy.on('proxyRes', function (proxyRes, req, res) {
                    modifyResponse(res, proxyRes, function (response) {
                        if (!MXMUtil.empty(response) && !MXMUtil.empty(response.message) && !MXMUtil.empty(response.message.body)) { // valid response
                            if (!MXMUtil.empty(response.message.body.error)) { // error response
                                var message = self.processor.createErrorMessage(500, '', response.message.body.error);
                                response = message;
                            } else { // valid response
                                var message = self.processor.prepareResponse(req_start, response.message.body);
                                response = message;
                        return response; // return value can be a promise
                proxy.on('error', function (error, req, res) {
                    var errorMessage = self.processor.createErrorMessage(500, '', error.message);
                proxy.web(req, res, {
                    //  url string to be parsed with the url module
                    target: target_uri,
                    //  true/false, Default: false - changes the origin of the host header to the target URL
                    changeOrigin: true,
                    //  true/false, Default: false - specify whether you want to ignore the proxy path of the incoming request 
                    ignorePath: true

the express uses bodyParser like

        // express app = express();
        // development || production'env', env);
        // custom logging: only error codes'combined', {
            skip: function (req, res) {
                return res.statusCode < 400;
        // LP: handle Error: request entity too large{limit: '50mb'}));{limit: '50mb', extended: true}));;; // gzip compression

I have also tried a simpler approach that was:

if (req.body && req.body.length) {
                        proxyReq.write(new Buffer(req.body[0]));

In that case I get a json decoding error, while the Can't set headers after they are sent disappeared. I think that this was due because in the examples above the proxyReq.end(); after proxyReq.write it is missing.

Here is my full code. I spent lot of time on this. I just posting this code to save your time.

const express = require('express');
const app = express();
const httpProxy = require('http-proxy');
const apiProxy = httpProxy.createProxyServer();
const server1 = 'http://localhost:4000',
	server2 = 'http://localhost:4001';

const bodyParser = require('body-parser');

	extended: true

 * added to resolve post and put request hanging
apiProxy.on('proxyReq', function (proxyReq, req, res, options) {
	if (req.body) {
		let bodyData = JSON.stringify(req.body);
		// incase if content-type is application/x-www-form-urlencoded -> we need to change to application/json
		proxyReq.setHeader('Content-Type', 'application/json');
		proxyReq.setHeader('Content-Length', Buffer.byteLength(bodyData));
		// stream the content

//TODO: Authtenticate Token
//TODO: Discover the service
//TODO: Authorize user
//TODO: Get the jwt token to call cloud function
//TODO: Make proxy request to cloud function

app.all('/service1/*', (req, res) => {
	apiProxy.web(req, res, { target: server1 });

app.all('/service2/*', (req, res) => {
	console.log(" request body  ... ", req.body);
	apiProxy.web(req, res, { target: server2 });

apiProxy.on('error', (err, req, res) => {
	console.log('got an error : ', err)

apiProxy.on('proxyRes', (proxyRes, req, res) => {
	console.log(' got a response from the server ..');
	return proxyRes;

app.listen(3000, () => console.log(' proxy running on 3000'));

module.exports = app;