http-proxy-middleware

What is http-proxy-middleware?

The http-proxy-middleware package is a Node.js package that provides an HTTP proxy as a middleware for use with Node.js applications, particularly in conjunction with frameworks like Express. It allows developers to easily set up proxy rules to forward requests to other servers, which is useful for tasks like API forwarding, logging, handling CORS, and more.

What are http-proxy-middleware's main functionalities?

Proxy requests

This feature allows you to proxy requests to another server. In this example, all requests to '/api' on the local server are forwarded to 'http://www.example.org'.

const { createProxyMiddleware } = require('http-proxy-middleware');

const apiProxy = createProxyMiddleware('/api', { target: 'http://www.example.org' });

app.use('/api', apiProxy);

Path Rewriting

This feature allows you to rewrite the path of the request URL before it gets proxied. In this example, the path '/api' is removed before the request is forwarded to 'http://www.example.org'.

const { createProxyMiddleware } = require('http-proxy-middleware');

const apiProxy = createProxyMiddleware('/api', {
  target: 'http://www.example.org',
  pathRewrite: { '^/api': '' }
});

app.use('/api', apiProxy);

Custom Routing Logic

This feature allows you to implement custom routing logic. In this example, only GET requests to paths starting with '/api' are proxied to 'http://www.example.org'.

const { createProxyMiddleware } = require('http-proxy-middleware');

const apiProxy = createProxyMiddleware((pathname, req) => {
  return pathname.match('^/api') && req.method === 'GET';
}, { target: 'http://www.example.org' });

app.use(apiProxy);

Handling WebSockets

This feature allows you to proxy WebSocket connections. In this example, WebSocket connections to '/socket' are proxied to 'ws://www.example.org'.

const { createProxyMiddleware } = require('http-proxy-middleware');

const wsProxy = createProxyMiddleware('/socket', {
  target: 'ws://www.example.org',
  ws: true
});

app.use('/socket', wsProxy);

Other packages similar to http-proxy-middleware

express-http-proxy

express-http-proxy is similar to http-proxy-middleware but is specifically designed for use with Express. It offers similar features for proxying HTTP requests but may have different configuration options and middleware setup.

node-http-proxy

node-http-proxy is a full-featured HTTP proxy library for Node.js, which http-proxy-middleware is built upon. It provides more low-level control over proxying but requires more setup compared to the convenience middleware layer provided by http-proxy-middleware.

redbird

Redbird is a reverse proxy library for Node.js with built-in support for clustering, HTTP2, LetsEncrypt, and more. It is more feature-rich and suitable for more complex proxying needs compared to http-proxy-middleware, which is simpler and more focused on middleware use cases.

README

http-proxy-middleware

Node.js proxying made simple. Configure proxy middleware with ease for connect, express and browser-sync.

Powered by the popular Nodejitsu http-proxy.

Install

$ npm install --save-dev http-proxy-middleware

Core concept

Configure the proxy middleware.

var proxyMiddleware = require('http-proxy-middleware');

var proxy = proxyMiddleware('/api', {target: 'http://www.example.org'});
//                          \____/  \________________________________/
//                            |                     |
//                          context              options

// 'proxy' is now ready to be used in a server.

• context: matches provided context against request-urls' path. Matching requests will be proxied to the target host. Example: '/api' or ['/api', '/ajax']. (more about context matching)
• options.target: target host to proxy to. Check out available proxy middleware options.

// shorthand syntax for the example above:
var proxy = proxyMiddleware('http://www.example.org/api');

More about the shorthand configuration.

Example

An example with express server.

// include dependencies
var express = require('express');
var proxyMiddleware = require('http-proxy-middleware');

// configure proxy middleware context
var context = '/api';                     // requests with this path will be proxied

// configure proxy middleware options
var options = {
        target: 'http://www.example.org', // target host
        changeOrigin: true,               // needed for virtual hosted sites
        ws: true,                         // proxy websockets
        pathRewrite: {
            '^/old/api' : '/new/api'      // rewrite paths
        },
        proxyTable: {
            // when request.headers.host == 'dev.localhost:3000',
            // override target 'http://www.example.org' to 'http://localhost:8000'
            'dev.localhost:3000' : 'http://localhost:8000'
        }
    };

// create the proxy
var proxy = proxyMiddleware(context, options);

// use the configured `proxy` in web server
var app = express();
    app.use(proxy);
    app.listen(3000);

Check out working examples.

Tip: For name-based virtual hosted sites, you'll need to use the option changeOrigin and set it to true.

Context matching

http-proxy-middleware offers several ways to decide which requests should be proxied. Request URL's path-absolute and query will be used for context matching .

• path matching

  • '/' - matches any path, all requests will be proxied.
  • '/api' - matches paths starting with /api

• multiple path matching

  • ['/api', '/ajax', '/someotherpath']

• wildcard path matching For fine-grained control you can use wildcard matching. Glob pattern matching is done by micromatch. Visit micromatch or glob for more globbing examples.

  • '**' matches any path, all requests will be proxied.
  • '**/*.html' matches any path which ends with .html
  • '/*.html' matches paths directly under path-absolute
  • '/api/**/*.html' matches requests ending with .html in the path of /api
  • ['/api/**', '/ajax/**'] combine multiple patterns
  • ['/api/**', '!**/bad.json'] exclusion

Shorthand

Use the shorthand syntax when verbose configuration is not needed. The context and option.target will be automatically configured when shorthand is used. Options can still be used if needed.

proxyMiddleware('http://www.example.org:8000/api');
// proxyMiddleware('/api', {target: 'http://www.example.org:8000'});


proxyMiddleware('http://www.example.org:8000/api/books/*/**.json');
// proxyMiddleware('/api/books/*/**.json', {target: 'http://www.example.org:8000'});


proxyMiddleware('http://www.example.org:8000/api', {changeOrigin:true});
// proxyMiddleware('/api', {target: 'http://www.example.org:8000', changeOrigin: true});

WebSocket

// verbose api
proxyMiddleware('/', {target:'http://echo.websocket.org', ws:true});

// shorthand
proxyMiddleware('http://echo.websocket.org', {ws:true});

// shorter shorthand
proxyMiddleware('ws://echo.websocket.org');

External WebSocket upgrade

In the previous WebSocket examples, http-proxy-middleware relies on a initial http request in order to listen to the http upgrade event. If you need to proxy WebSockets without the initial http request, you can subscribe to the server's http upgrade event manually.

var proxy = proxyMiddleware('ws://echo.websocket.org', {changeOrigin:true});

var app = express();
    app.use(proxy);

var server = app.listen(3000);
    server.on('upgrade', proxy.upgrade);    // <-- subscribe to http 'upgrade'

Options

• option.pathRewrite: object, rewrite target's url path. Object-keys will be used as RegExp to match paths.

  {
      "^/old/api" : "/new/api",    // rewrite path
      "^/remove/api" : ""          // remove path
  }
  

• option.proxyTable: object, re-target option.target based on the request header host parameter. host can be used in conjunction with path. Only one instance of the proxy will be used. The order of the configuration matters.

  {
      "integration.localhost:3000" : "http://localhost:8001",    // host only
      "staging.localhost:3000"     : "http://localhost:8002",    // host only
      "localhost:3000/api"         : "http://localhost:8003",    // host + path
      "/rest"                      : "http://localhost:8004"     // path only
  }
  

• option.logLevel: string, ['debug', 'info', 'warn', 'error', 'silent']. Default: 'info'

• option.logProvider: function, modify or replace log provider. Default: console.

  // simple replace
  function logProvider(provider) {
      // replace the default console log provider.
      return require('winston');
  }
  

  // verbose replacement
  function logProvider(provider) {
      var logger = new (require('winston').Logger)();
  
      var myCustomProvider = {
          log: logger.log,
          debug: logger.debug,
          info: logger.info,
          warn: logger.warn,
          error: logger.error
      }
      return myCustomProvider;
  }
  

• option.onError: function, subscribe to http-proxy's error event for custom error handling.

  function onError(err, req, res) {
      res.writeHead(500, {
          'Content-Type': 'text/plain'
      });
      res.end('Something went wrong. And we are reporting a custom error message.');
  }
  

• option.onProxyRes: function, subscribe to http-proxy's proxyRes event.

  function onProxyRes(proxyRes, req, res) {
      proxyRes.headers['x-added'] = 'foobar';     // add new header to response
      delete proxyRes.headers['x-removed'];       // remove header from response
  }
  

• option.onProxyReq: function, subscribe to http-proxy's proxyReq event.

  function onProxyReq(proxyReq, req, res) {
      // add custom header to request
      proxyReq.setHeader('x-added', 'foobar');
      // or log the req
  }
  

• (DEPRECATED) option.proxyHost: Use option.changeOrigin = true instead.

The following options are provided by the underlying http-proxy.

• option.target: url string to be parsed with the url module
• option.forward: url string to be parsed with the url module
• option.agent: object to be passed to http(s).request (see Node's https agent and http agent objects)
• option.ssl: object to be passed to https.createServer()
• option.ws: true/false: if you want to proxy websockets
• option.xfwd: true/false, adds x-forward headers
• option.secure: true/false, if you want to verify the SSL Certs
• option.toProxy: passes the absolute URL as the path (useful for proxying to proxies)
• option.prependPath: true/false, Default: true - specify whether you want to prepend the target's path to the proxy path>
• option.ignorePath: true/false, Default: false - specify whether you want to ignore the proxy path of the incoming request>
• option.localAddress : Local interface string to bind for outgoing connections
• option.changeOrigin: true/false, adds host to request header.
• option.auth : Basic authentication i.e. 'user:password' to compute an Authorization header.
• option.hostRewrite: rewrites the location hostname on (301/302/307/308) redirects.
• option.autoRewrite: rewrites the location host/port on (301/302/307/308) redirects based on requested host/port. Default: false.
• option.protocolRewrite: rewrites the location protocol on (301/302/307/308) redirects to 'http' or 'https'. Default: null.

Undocumented options are provided by the underlying http-proxy

• option.headers: object, adds request headers. (Example: {host:'www.example.org'}) source

Recipes

View the recipes for common use cases.

More Examples

To run and view the proxy examples, clone the http-proxy-middleware repo and install the dependencies:

$ git clone https://github.com/chimurai/http-proxy-middleware.git
$ cd http-proxy-middleware
$ npm install

Run the example:

$ node examples/connect

Or just explore the proxy examples' sources:

• examples/connect - connect proxy example
• examples/express - express proxy example
• examples/browser-sync - browser-sync proxy example
• examples/websocket - websocket proxy example with express

Compatible servers

http-proxy-middleware is compatible with the following servers:

• connect
• express
• browser-sync

Tests

To run the test suite, first install the dependencies, then run:

# install dependencies
$ npm install

# unit tests
$ npm test

# code coverage
$ npm run cover

Changelog

• View changelog

License

The MIT License (MIT)

Copyright (c) 2015 Steven Chim