@hmcts/http-proxy-middleware

v1.1.3

Published

3 years ago

The one-liner node.js proxy middleware for connect, express and browser-sync

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http-proxy-middleware

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

⚠️ Note

This page is showing documentation for version v1.x.x (release notes)

If you're looking for v0.x documentation. Go to: https://github.com/chimurai/http-proxy-middleware/tree/v0.21.0#readme

TL;DR

Proxy /api requests to http://www.example.org

// javascript

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

const app = express();

app.use('/api', createProxyMiddleware({ target: 'http://www.example.org', changeOrigin: true }));
app.listen(3000);

// http://localhost:3000/api/foo/bar -> http://www.example.org/api/foo/bar

// typescript

import * as express from 'express';
import { createProxyMiddleware, Filter, Options, RequestHandler } from 'http-proxy-middleware';

const app = express();

app.use('/api', createProxyMiddleware({ target: 'http://www.example.org', changeOrigin: true }));
app.listen(3000);

// http://localhost:3000/api/foo/bar -> http://www.example.org/api/foo/bar

All http-proxy options can be used, along with some extra http-proxy-middleware options.

:bulb: Tip: Set the option changeOrigin to true for name-based virtual hosted sites.

Install

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

Core concept

Proxy middleware configuration.

createProxyMiddleware([context,] config)

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

const apiProxy = createProxyMiddleware('/api', { target: 'http://www.example.org' });
//                                    \____/   \_____________________________/
//                                      |                    |
//                                    context             options

// 'apiProxy' is now ready to be used as middleware in a server.

context: Determine which requests should be proxied to the target host. (more on context matching)
options.target: target host to proxy to. (protocol + host)

(full list of http-proxy-middleware configuration options)

createProxyMiddleware(uri [, config])

// shorthand syntax for the example above:
const apiProxy = createProxyMiddleware('http://www.example.org/api');

More about the shorthand configuration.

Example

An example with express server.

// include dependencies
const express = require('express');
const { createProxyMiddleware } = require('http-proxy-middleware');

// proxy middleware options
const options = {
  target: 'http://www.example.org', // target host
  changeOrigin: true, // needed for virtual hosted sites
  ws: true, // proxy websockets
  pathRewrite: {
    '^/api/old-path': '/api/new-path', // rewrite path
    '^/api/remove/path': '/path', // remove base path
  },
  router: {
    // 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 (without context)
const exampleProxy = createProxyMiddleware(options);

// mount `exampleProxy` in web server
const app = express();
app.use('/api', exampleProxy);
app.listen(3000);

Context matching

Providing an alternative way to decide which requests should be proxied; In case you are not able to use the server's path parameter to mount the proxy or when you need more flexibility.

RFC 3986 path is used for context matching.

         foo://example.com:8042/over/there?name=ferret#nose
         \_/   \______________/\_________/ \_________/ \__/
          |           |            |            |        |
       scheme     authority       path        query   fragment

path matching
- createProxyMiddleware({...}) - matches any path, all requests will be proxied.
- createProxyMiddleware('/', {...}) - matches any path, all requests will be proxied.
- createProxyMiddleware('/api', {...}) - matches paths starting with /api
multiple path matching
- createProxyMiddleware(['/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.
- createProxyMiddleware('**', {...}) matches any path, all requests will be proxied.
- createProxyMiddleware('**/*.html', {...}) matches any path which ends with .html
- createProxyMiddleware('/*.html', {...}) matches paths directly under path-absolute
- createProxyMiddleware('/api/**/*.html', {...}) matches requests ending with .html in the path of /api
- createProxyMiddleware(['/api/**', '/ajax/**'], {...}) combine multiple patterns
- createProxyMiddleware(['/api/**', '!**/bad.json'], {...}) exclusion
Note: In multiple path matching, you cannot use string paths and wildcard paths together.

custom matching

For full control you can provide a custom function to determine which requests should be proxied or not.

/**
 * @return {Boolean}
 */
const filter = function (pathname, req) {
  return pathname.match('^/api') && req.method === 'GET';
};

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

Options

http-proxy-middleware options

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

// rewrite path
pathRewrite: {'^/old/api' : '/new/api'}

// remove path
pathRewrite: {'^/remove/api' : ''}

// add base path
pathRewrite: {'^/' : '/basepath/'}

// custom rewriting
pathRewrite: function (path, req) { return path.replace('/api', '/base/api') }

// custom rewriting, returning Promise
pathRewrite: async function (path, req) {
  const should_add_something = await httpRequestToDecideSomething(path);
  if (should_add_something) path += "something";
  return path;
}

option.router: object/function, re-target option.target for specific requests.

// Use `host` and/or `path` to match requests. First match will be used.
// The order of the configuration matters.
router: {
    '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
}

// Custom router function (string target)
router: function(req) {
    return 'http://localhost:8004';
}

// Custom router function (target object)
router: function(req) {
    return {
        protocol: 'https:', // The : is required
        host: 'localhost',
        port: 8004
    };
}

// Asynchronous router function which returns promise
router: async function(req) {
    const url = await doSomeIO();
    return url;
}

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) {
  const logger = new (require('winston').Logger)();

  const myCustomProvider = {
    log: logger.log,
    debug: logger.debug,
    info: logger.info,
    warn: logger.warn,
    error: logger.error,
  };
  return myCustomProvider;
}

http-proxy events

Subscribe to http-proxy events:

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

function onError(err, req, res, target) {
  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
}

option.onProxyReqWs: function, subscribe to http-proxy's proxyReqWs event.

function onProxyReqWs(proxyReq, req, socket, options, head) {
  // add custom header
  proxyReq.setHeader('X-Special-Proxy-Header', 'foobar');
}

option.onOpen: function, subscribe to http-proxy's open event.

function onOpen(proxySocket) {
  // listen for messages coming FROM the target here
  proxySocket.on('data', hybiParseAndLogMessage);
}

option.onClose: function, subscribe to http-proxy's close event.

function onClose(res, socket, head) {
  // view disconnected websocket connections
  console.log('Client disconnected');
}

http-proxy options

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

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: true/false, 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 (note: you will have to append / manually if required).
option.localAddress : Local interface string to bind for outgoing connections
option.changeOrigin: true/false, Default: false - changes the origin of the host header to the target URL
option.preserveHeaderKeyCase: true/false, Default: false - specify whether you want to keep letter case of response header key
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.
option.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",
  "*": ""
}
```
option.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/",
  "*": ""
}
```
option.headers: object, adds request headers. (Example: {host:'www.example.org'})
option.proxyTimeout: timeout (in millis) when proxy receives no response from target
option.timeout: timeout (in millis) for incoming requests
option.followRedirects: true/false, Default: false - specify whether you want to follow redirects
option.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

option.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
  );
};

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.

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

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

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

app.use(path, proxy)

If you want to use the server's app.use path parameter to match requests; Create and mount the proxy without the http-proxy-middleware context parameter:

app.use('/api', createProxyMiddleware({ target: 'http://www.example.org', changeOrigin: true }));

app.use documentation:

express: http://expressjs.com/en/4x/api.html#app.use
connect: https://github.com/senchalabs/connect#mount-middleware
polka: https://github.com/lukeed/polka#usebase-fn

WebSocket

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

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

// shorter shorthand
createProxyMiddleware('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.

const wsProxy = createProxyMiddleware('ws://echo.websocket.org', { changeOrigin: true });

const app = express();
app.use(wsProxy);

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

Working examples

View and play around with working examples.

Browser-Sync (example source)
express (example source)
connect (example source)
WebSocket (example source)

Recipes

View the recipes for common use cases.

Compatible servers

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

Sample implementations can be found in the server recipes.

Tests

Run the test suite:

# install dependencies
$ yarn

# linting
$ yarn lint
$ yarn lint:fix

# building (compile typescript to js)
$ yarn build

# unit tests
$ yarn test

# code coverage
$ yarn cover

Changelog

View changelog

License

The MIT License (MIT)