http-proxy

http-proxy is an HTTP programmable proxying library that supports websockets. It is suitable for implementing components such as reverse proxies and load balancers.

Table of Contents

• Installation
• Upgrading from 0.8.x ?
• Core Concept
• Use Cases
  • Setup a basic stand-alone proxy server
  • Setup a stand-alone proxy server with custom server logic
  • Setup a stand-alone proxy server with proxy request header re-writing
  • Modify a response from a proxied server
  • Setup a stand-alone proxy server with latency
  • Using HTTPS
  • Proxying WebSockets
• Options
• Listening for proxy events
• Shutdown
• Miscellaneous
  • Test
  • ProxyTable API
  • Logo
• Contributing and Issues

Installation

npm install @nrayburn-tech/http-proxy --save

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Upgrading from 0.8.x ?

Click here

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Core Concept

A new proxy is created by calling createProxy and passing an options object as an argument (valid properties are available here)

import { createProxy, ProxyServerOptions } from 'http-proxy';

const options: ProxyServerOptions = {};

const proxy = createProxy(options); // See (†)

†Unless listen(..) is invoked on the object, this does not create a webserver. See below.

An object will be returned with four methods:

• web req, res, [options] (used for proxying regular HTTP(S) requests)
• ws req, socket, head, [options] (used for proxying WS(S) requests)
• listen port, [hostname] (a function that wraps the object in a webserver, for your convenience)
• close [callback] (a function that closes the inner webserver and stops listening on given port)

It is then possible to proxy requests by calling these functions

http.createServer(function (
  req: http.IncomingMessage,
  res: http.ServerResponse,
) {
  proxy.web(req, res);
});

It is also possible to pass in options for specific proxy calls, to override the options used when creating the proxy.

http.createServer(function (
  req: http.IncomingMessage,
  res: http.ServerResponse,
) {
  if (req.url.includes('/api/user')) {
    proxy.web(req, res, { target: 'http://internal.api/user' });
  }
});

Errors can be listened on either using the Event Emitter API

proxy.on('error', function(e) {
  ...
});

or using the callback API

proxy.web(req, res, { target: 'http://mytarget.com:8080' }, function(e) { ... });

When a request is proxied it follows two different pipelines (available here) which apply transformations to both the req and res object. The first pipeline (incoming) is responsible for the creation and manipulation of the stream that connects your client to the target. The second pipeline (outgoing) is responsible for the creation and manipulation of the stream that, from your target, returns data to the client.

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Use Cases

Setup a basic stand-alone proxy server

import * as http from 'http';
import { createProxy } from 'http-proxy';

// Create your proxy server and set the target in the options.
createProxy({ target: 'http://localhost:9000' }).listen(8000); // See (†)

// Create your target server
http
  .createServer(function (req, res) {
    res.writeHead(200, { 'Content-Type': 'text/plain' });
    res.write(
      'request successfully proxied!' +
        '\n' +
        JSON.stringify(req.headers, true, 2),
    );
    res.end();
  })
  .listen(9000);

†Invoking listen(..) triggers the creation of a web server. Otherwise, just the proxy instance is created.

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Setup a stand-alone proxy server with custom server logic

This example shows how you can proxy a request using your own HTTP server and also you can put your own logic to handle the request.

import * as http from 'http';
import { createProxy } from 'http-proxy';

// Create a proxy server with custom application logic
const proxy = createProxy({});

// Create your custom server and just call `proxy.web()` to proxy
// a web request to the target passed in the options
// also you can use `proxy.ws()` to proxy a websockets request
const server = http.createServer(function (
  req: http.IncomingMessage,
  res: http.ServerResponse,
) {
  // You can define here your custom logic to handle the request
  // and then proxy the request.
  proxy.web(req, res, { target: 'http://127.0.0.1:5050' });
});

console.log('listening on port 5050');
server.listen(5050);

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Setup a stand-alone proxy server with proxy request header re-writing

This example shows how you can proxy a request using your own HTTP server that modifies the outgoing proxy request by adding a special header.

import * as http from 'http';
import { createProxy, ProxyServerOptions } from 'http-proxy';

// Create a proxy server with custom application logic
const proxy = createProxy({});

// To modify the proxy connection before data is sent, you can listen
// for the 'proxyReq' event. When the event is fired, you will receive
// the following arguments:
// (http.ClientRequest proxyReq, http.IncomingMessage req,
//  http.ServerResponse res, Object options). This mechanism is useful when
// you need to modify the proxy request before the proxy connection
// is made to the target.
proxy.on(
  'proxyReq',
  function (
    proxyReq: http.ClientRequest,
    req: http.IncomingMessage,
    res: http.ServerResponse,
    options: ProxyServerOptions,
  ) {
    proxyReq.setHeader('X-Special-Proxy-Header', 'foobar');
  },
);

const server = http.createServer(function (
  req: http.IncomingMessage,
  res: http.ServerResponse,
) {
  // You can define here your custom logic to handle the request
  // and then proxy the request.
  proxy.web(req, res, {
    target: 'http://127.0.0.1:5050',
  });
});

server.listen(5050, () => {
  console.log('listening on port 5050');
});

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Modify a response from a proxied server

Sometimes when you have received a HTML/XML document from the server of origin you would like to modify it before forwarding it on.

Harmon allows you to do this in a streaming style so as to keep the pressure on the proxy to a minimum.

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Setup a stand-alone proxy server with latency

import * as http from 'http';
import { createProxy } from 'http-proxy';

// Create a proxy server with latency
var proxy = createProxy();

// Create your server that makes an operation that waits a while
// and then proxies the request
http
  .createServer(function (req, res) {
    // This simulates an operation that takes 500ms to execute
    setTimeout(function () {
      proxy.web(req, res, {
        target: 'http://localhost:9008',
      });
    }, 500);
  })
  .listen(8008);

// Create your target server
http
  .createServer(function (req, res) {
    res.writeHead(200, { 'Content-Type': 'text/plain' });
    res.write(
      'request successfully proxied to: ' +
        req.url +
        '\n' +
        JSON.stringify(req.headers, true, 2),
    );
    res.end();
  })
  .listen(9008);

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Using HTTPS

You can activate the validation of a secure SSL certificate to the target connection (avoid self-signed certs), just set secure: true in the options.

HTTPS -> HTTP

// Create the HTTPS proxy server in front of a HTTP server
createProxy({
  target: {
    host: 'localhost',
    port: 9009,
  },
  ssl: {
    key: fs.readFileSync('valid-ssl-key.pem', 'utf8'),
    cert: fs.readFileSync('valid-ssl-cert.pem', 'utf8'),
  },
}).listen(8009);

HTTPS -> HTTPS

// Create the proxy server listening on port 443
createProxy({
  ssl: {
    key: fs.readFileSync('valid-ssl-key.pem', 'utf8'),
    cert: fs.readFileSync('valid-ssl-cert.pem', 'utf8'),
  },
  target: 'https://localhost:9010',
  secure: true, // Depends on your needs, could be false.
}).listen(443);

HTTP -> HTTPS (using a PKCS12 client certificate)

// Create an HTTP proxy server with an HTTPS target
createProxy({
  target: {
    protocol: 'https:',
    host: 'my-domain-name',
    port: 443,
    pfx: fs.readFileSync('path/to/certificate.p12'),
    passphrase: 'password',
  },
  changeOrigin: true,
}).listen(8000);

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Proxying WebSockets

You can activate the websocket support for the proxy using ws:true in the options.

// Create a proxy server for websockets
createProxy({
  target: 'ws://localhost:9014',
  ws: true,
}).listen(8014);

Also, you can proxy the websocket requests just calling the ws(req, socket, head) method.

// Setup our server to proxy standard HTTP requests
const proxy = createProxy({
  target: {
    host: 'localhost',
    port: 9015,
  },
});
const proxyServer = http.createServer(function (req, res) {
  proxy.web(req, res);
});

// Listen to the `upgrade` event and proxy the
// WebSocket requests as well.
proxyServer.on('upgrade', function (req, socket, head) {
  proxy.ws(req, socket, head);
});

proxyServer.listen(8015);

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Options

createProxy supports the following options:

• target: url string to be parsed with the url module

• forward: url string to be parsed with the url module

• agent: object to be passed to http(s).request (see Node's https agent and http agent objects)

• ssl: object to be passed to https.createServer()

• ws: true/false, if you want to proxy websockets

• xfwd: true/false, adds x-forward headers

• secure: true/false, if you want to verify the SSL Certs

• toProxy: true/false, passes the absolute URL as the path (useful for proxying to proxies)

• prependPath: true/false, Default: true - specify whether you want to prepend the target's path to the proxy path

• ignorePath: true/false, Default: false - specify whether you want to ignore the proxy path of the incoming request (note: you will have to append / manually if required).

• localAddress: Local interface string to bind for outgoing connections

• changeOrigin: true/false, Default: false - changes the origin of the host header to the target URL

• preserveHeaderKeyCase: true/false, Default: false - specify whether you want to keep letter case of response header key

• auth: Basic authentication i.e. 'user:password' to compute an Authorization header.

• hostRewrite: rewrites the location hostname on (201/301/302/307/308) redirects.

• autoRewrite: rewrites the location host/port on (201/301/302/307/308) redirects based on requested host/port. Default: false.

• protocolRewrite: rewrites the location protocol on (201/301/302/307/308) redirects to 'http' or 'https'. Default: null.

• cookieDomainRewrite: rewrites domain of set-cookie headers. Possible values:

  • false (default): disable cookie rewriting
  • String: new domain, for example cookieDomainRewrite: "new.domain". To remove the domain, use cookieDomainRewrite: "".
  • Object: mapping of domains to new domains, use "*" to match all domains. For example keep one domain unchanged, rewrite one domain and remove other domains:

    cookieDomainRewrite: {
      "unchanged.domain": "unchanged.domain",
      "old.domain": "new.domain",
      "*": ""
    }
    

• cookiePathRewrite: rewrites path of set-cookie headers. Possible values:

  • false (default): disable cookie rewriting
  • String: new path, for example cookiePathRewrite: "/newPath/". To remove the path, use cookiePathRewrite: "". To set path to root use cookiePathRewrite: "/".
  • Object: mapping of paths to new paths, use "*" to match all paths. For example, to keep one path unchanged, rewrite one path and remove other paths:

    cookiePathRewrite: {
      "/unchanged.path/": "/unchanged.path/",
      "/old.path/": "/new.path/",
      "*": ""
    }
    

• headers: object with extra headers to be added to target requests.

• proxyTimeout: timeout (in millis) for outgoing proxy requests

• timeout: timeout (in millis) for incoming requests

• followRedirects: true/false, Default: false - specify whether you want to follow redirects

• selfHandleResponse true/false, if set to true, none of the webOutgoing passes are called and it's your responsibility to appropriately return the response by listening and acting on the proxyRes event

• buffer: stream of data to send as the request body. Maybe you have some middleware that consumes the request stream before proxying it on e.g. If you read the body of a request into a field called 'req.rawbody' you could restream this field in the buffer option:

  'use strict';
  
  const streamify = require('stream-array');
  const HttpProxy = require('http-proxy');
  const proxy = new HttpProxy();
  
  module.exports = (req, res, next) => {
  
    proxy.web(req, res, {
      target: 'http://localhost:4003/',
      buffer: streamify(req.rawBody)
    }, next);
  
  };
  

NOTE: options.ws and options.ssl are optional. options.target and options.forward cannot both be missing

If you are using the proxyServer.listen method, the following options are also applicable:

• ssl: object to be passed to https.createServer()
• ws: true/false, if you want to proxy websockets

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Listening for proxy events

• error: The error event is emitted if the request to the target fail. We do not do any error handling of messages passed between client and proxy, and messages passed between proxy and target, so it is recommended that you listen on errors and handle them.
• proxyReq: This event is emitted before the data is sent. It gives you a chance to alter the proxyReq request object. Applies to "web" connections
• proxyReqWs: This event is emitted before the data is sent. It gives you a chance to alter the proxyReq request object. Applies to "websocket" connections
• proxyRes: This event is emitted if the request to the target got a response.
• open: This event is emitted once the proxy websocket was created and piped into the target websocket.
• close: This event is emitted once the proxy websocket was closed.
• (DEPRECATED) proxySocket: Deprecated in favor of open.

import { createProxy } from 'http-proxy';
// Error example

// Http Proxy Server with bad target
const proxy = createProxy({
  target: 'http://localhost:9005',
});

proxy.listen(8005);

// Listen for the `error` event on `proxy`.
proxy.on('error', function (err, req, res) {
  res.writeHead(500, {
    'Content-Type': 'text/plain',
  });

  res.end('Something went wrong. And we are reporting a custom error message.');
});

// Listen for the `proxyRes` event on `proxy`.
proxy.on('proxyRes', function (proxyRes, req, res) {
  console.log(
    'RAW Response from the target',
    JSON.stringify(proxyRes.headers, true, 2),
  );
});

// Listen for the `open` event on `proxy`.
proxy.on('open', function (proxySocket) {
  // listen for messages coming FROM the target here
  proxySocket.on('data', hybiParseAndLogMessage);
});

// Listen for the `close` event on `proxy`.
proxy.on('close', function (res, socket, head) {
  // view disconnected websocket connections
  console.log('Client disconnected');
});

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Shutdown

• When testing or running server within another program it may be necessary to close the proxy.
• This will stop the proxy from accepting new connections.

const proxy = createProxy({
  target: {
    host: 'localhost',
    port: 1337,
  },
});

proxy.close();

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Miscellaneous

If you want to handle your own response after receiving the proxyRes, you can do so with selfHandleResponse. As you can see below, if you use this option, you are able to intercept and read the proxyRes but you must also make sure to reply to the res itself otherwise the original client will never receive any data.

Modify response

import { ProxyServerOptions } from './proxyServer';

const option: ProxyServerOptions = {
  target: target,
  selfHandleResponse: true,
};
proxy.on(
  'proxyRes',
  function (
    proxyRes: http.IncomingMessage,
    req: http.IncomingMessage,
    res: http.ServerResponse,
  ) {
    let body = [];
    proxyRes.on('data', function (chunk) {
      body.push(chunk);
    });
    proxyRes.on('end', function () {
      body = Buffer.concat(body).toString();
      console.log('res from proxied server:', body);
      res.end('my response to cli');
    });
  },
);
proxy.web(req, res, option);

ProxyTable API

A proxy table API is available through this add-on module, which lets you define a set of rules to translate matching routes to target routes that the reverse proxy will talk to.

Test

$ npm test

Logo

Logo created by Diego Pasquali

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Contributing and Issues

• Read carefully our Code Of Conduct
• Search on Google/Github
• If you can't find anything, open an issue
• If you feel comfortable about fixing the issue, fork the repo
• Commit to your local branch (which must be different from main)
• Submit your Pull Request (be sure to include tests and update documentation)

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