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node-http-proxy.js

/*
  node-http-proxy.js: http proxy for node.js

  Copyright (c) 2010 Charlie Robbins, Mikeal Rogers, Marak Squires, Fedor Indutny 

  Permission is hereby granted, free of charge, to any person obtaining
  a copy of this software and associated documentation files (the
  "Software"), to deal in the Software without restriction, including
  without limitation the rights to use, copy, modify, merge, publish,
  distribute, sublicense, and/or sell copies of the Software, and to
  permit persons to whom the Software is furnished to do so, subject to
  the following conditions:

  The above copyright notice and this permission notice shall be
  included in all copies or substantial portions of the Software.

  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
  LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
  OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
  WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

*/

var util = require('util'),
    http = require('http'),
    https = require('https'),
    events = require('events'),
    ProxyTable = require('./proxy-table').ProxyTable,
    maxSockets = 100;

Version 0.5.7 // 5/19/2011

exports.version = [0, 5, 7];

Track our own list of agents internal to node-http-proxy

var _agents = {};

function _getAgent (host, port, secure)

@host {string} Host of the agent to get

@port {number} Port of the agent to get

@secure {boolean} Value indicating whether or not to use HTTPS

Retreives an agent from the http or https module and sets the maxSockets property appropriately.

function _getAgent (host, port, secure) {
  var Agent, id = [host, port].join(':');
  
  if (!port) {
    port = secure ? 443 : 80;
  }
  
  if (!_agents[id]) {
    Agent = secure ? https.Agent : http.Agent;

    _agents[id] = new Agent({ 
      host: host, 
      port: port,
      maxSockets: maxSockets
    });
  }

  return _agents[id];
}

function _getProtocol (secure, outgoing)

@secure {Object|boolean} Settings for https

@outgoing {Object} Outgoing request options

Returns the appropriate protocol based on the settings in secure. If the protocol is https this function will update the options in outgoing as appropriate by adding ca, key, and cert if they exist in secure.

function _getProtocol (secure, outgoing) {
  var protocol = secure ? https : http;
  
  if (typeof secure === 'object') {
    outgoing = outgoing || {};
    ['ca', 'cert', 'key'].forEach(function (prop) {
      if (secure[prop]) {
        outgoing[prop] = secure[prop];
      }
    })
  }
  
  return protocol;
}

function getMaxSockets ()

Returns the maximum number of sockets allowed on every outgoing request made by all instances of HttpProxy

exports.getMaxSockets = function () {
  return maxSockets;
};

function setMaxSockets ()

Sets the maximum number of sockets allowed on every outgoing request made by all instances of HttpProxy

exports.setMaxSockets = function (value) {
  maxSockets = value;
};

function createServer ([port, host, options, handler])

@port {number} Optional Port to use on the proxy target host.

@host {string} Optional Host of the proxy target.

@options {Object} Optional Options for the HttpProxy instance used

@handler {function} Optional Request handler for the server

Returns a server that manages an instance of HttpProxy. Flexible arguments allow for:

  • httpProxy.createServer(9000, 'localhost')
  • `httpProxy.createServer(9000, 'localhost', options)
  • httpPRoxy.createServer(function (req, res, proxy) { ... })
exports.createServer = function () {
  var args = Array.prototype.slice.call(arguments), 
      callback = typeof args[0] === 'function' && args.shift(),
      options = {}, port, host, forward, silent, proxy, server;
  
  if (args.length >= 2) {
    port = args[0];
    host = args[1];
    options = args[2] || {};
  } 
  else if (args.length === 1) {
    options = args[0] || {};
    if (!options.router && !callback) {
      throw new Error('Cannot create server with no router and no callback');
    }
  }

  proxy = new HttpProxy(options);
  
  handler = function (req, res) {
    if (callback) {

If we were passed a callback to process the request or response in some way, then call it.

      callback(req, res, proxy);
    } 
    else if (port && host) {

If we have a target host and port for the request then proxy to the specified location.

      proxy.proxyRequest(req, res, {
        port: port, 
        host: host
      });
    }
    else if (proxy.proxyTable) {

If the proxy is configured with a ProxyTable instance then use that before failing.

      proxy.proxyRequest(req, res);
    }
    else {

Otherwise this server is improperly configured.

      throw new Error('Cannot proxy without port, host, or router.')
    }
  };
  
  server = options.https 
    ? https.createServer(options.https, handler)
    : http.createServer(handler);
  
  server.on('close', function () {
    proxy.close();
  });
  
  proxy.on('routes', function (routes) {
    server.emit('routes', routes);
  });

  if (!callback) {

WebSocket support: if callback is empty tunnel websocket request automatically

    server.on('upgrade', function (req, socket, head) {

Tunnel websocket requests too

      
      proxy.proxyWebSocketRequest(req, socket, head, {
        port: port,
        host: host
      });
    });
  }
  

Set the proxy on the server so it is available to the consumer of the server

  server.proxy = proxy;
  
  return server;
};

function HttpProxy (options)

@options {Object} Options for this instance.

Constructor function for new instances of HttpProxy responsible for managing the life-cycle of streaming reverse proxyied HTTP requests.

Example options:

 {
   router: {
     'foo.com': 'localhost:8080',
     'bar.com': 'localhost:8081'
   },
   forward: {
     host: 'localhost',
     port: 9001
   }
 } 
var HttpProxy = exports.HttpProxy = function (options) {
  events.EventEmitter.call(this);
  
  var self          = this;
  options           = options || {};
  

Setup basic proxying options

  this.https        = options.https;
  this.forward      = options.forward;
  this.target       = options.target || {};
  

Setup additional options for WebSocket proxying. When forcing the WebSocket handshake to change the sec-websocket-location and sec-websocket-origin headers options.source MUST be provided or the operation will fail with an origin mismatch by definition.

  this.source       = options.source || { host: 'localhost', port: 8000 };
  this.changeOrigin = options.changeOrigin || false;
  
  if (options.router) {
    this.proxyTable = new ProxyTable(options.router, options.silent, options.hostnameOnly);
    this.proxyTable.on('routes', function (routes) {
      self.emit('routes', routes);
    });
  }
};

Inherit from events.EventEmitter

util.inherits(HttpProxy, events.EventEmitter);

function buffer (obj)

@obj {Object} Object to pause events from

Buffer data and end events from the given obj. Consumers of HttpProxy performing async tasks must utilize this utility, to re-emit data once the async operation has completed, otherwise these events will be lost.

 var buffer = httpProxy.buffer(req);
 fs.readFile(path, function(){
    httpProxy.proxyRequest(req, res, host, port, buffer);
 });

Attribution: This approach is based heavily on Connect. However, this is not a big leap from the implementation in node-http-proxy < 0.4.0. This simply chooses to manage the scope of the events on a new Object literal as opposed to on the HttpProxy instance.

HttpProxy.prototype.buffer = function (obj) {
  var onData, onEnd, events = [];

  obj.on('data', onData = function (data, encoding) {
    events.push(['data', data, encoding]);
  });

  obj.on('end', onEnd = function (data, encoding) {
    events.push(['end', data, encoding]);
  });

  return {
    end: function () {
      obj.removeListener('data', onData);
      obj.removeListener('end', onEnd);
    },
    resume: function () {
      this.end();
      for (var i = 0, len = events.length; i < len; ++i) {
        obj.emit.apply(obj, events[i]);
      }
    }
  };
};

function close ()

Frees the resources associated with this instance, if they exist.

HttpProxy.prototype.close = function () {
  if (this.proxyTable) this.proxyTable.close();
};

function proxyRequest (req, res, [port, host, paused])

@req {ServerRequest} Incoming HTTP Request to proxy.

@res {ServerResponse} Outgoing HTTP Request to write proxied data to.

@options {Object} Options for the outgoing proxy request.

options.port {number} Port to use on the proxy target host.
options.host {string} Host of the proxy target.
options.buffer {Object} Result from `httpProxy.buffer(req)`
options.https {Object|boolean} Settings for https.
HttpProxy.prototype.proxyRequest = function (req, res, options) {
  var self = this, errState = false, location, outgoing, protocol, reverseProxy;
  

Create an empty options hash if none is passed. If default options have been passed to the constructor of this instance, use them by default.

  options      = options || {};
  options.host = options.host || this.target.host;
  options.port = options.port || this.target.port;
  

Check the proxy table for this instance to see if we need to get the proxy location for the request supplied. We will always ignore the proxyTable if an explicit port and host arguments are supplied to proxyRequest.

  if (this.proxyTable && !options.host) {
    location = this.proxyTable.getProxyLocation(req);
    

If no location is returned from the ProxyTable instance then respond with 404 since we do not have a valid proxy target.

    if (!location) {
      res.writeHead(404);
      return res.end();
    }
    

When using the ProxyTable in conjunction with an HttpProxy instance only the following arguments are valid:

  • proxy.proxyRequest(req, res, { host: 'localhost' }): This will be skipped
  • proxy.proxyRequest(req, res, { buffer: buffer }): Buffer will get updated appropriately
  • proxy.proxyRequest(req, res): Options will be assigned appropriately.
    options.port = location.port;
    options.host = location.host;
  }
  

Add common proxy headers to the request so that they can be availible to the proxy target server:

  • x-forwarded-for: IP Address of the original request
  • x-forwarded-proto: Protocol of the original request
  • x-forwarded-port: Port of the original request.
  req.headers['x-forwarded-for']   = req.connection.remoteAddress || req.connection.socket.remoteAddress;
  req.headers['x-forwarded-port']  = req.connection.remotePort || req.connection.socket.remotePort;
  req.headers['x-forwarded-proto'] = res.connection.pair ? 'https' : 'http';
  

Emit the start event indicating that we have begun the proxy operation.

  this.emit('start', req, res, options);
  

If forwarding is enabled for this instance, foward proxy the specified request to the address provided in this.forward

  if (this.forward) {
    this.emit('forward', req, res, this.forward);
    this._forwardRequest(req);
  }
  

function proxyError (err)

@err {Error} Error contacting the proxy target

Short-circuits res in the event of any error when contacting the proxy target at host / port.

  function proxyError(err) {
    errState = true;
    

Emit an error event, allowing the application to use custom error handling. The error handler should end the response.

    if (self.emit('proxyError', err, req, res)) {
      return;
    }

    res.writeHead(500, { 'Content-Type': 'text/plain' });

    if (req.method !== 'HEAD') {

This NODE_ENV=production behavior is mimics Express and Connect.

      if (process.env.NODE_ENV === 'production') {
        res.write('Internal Server Error');
      }
      else {
        res.write('An error has occurred: ' + JSON.stringify(err));
      }
    }
  
    res.end();
  }
  
  outgoing = {
    host: options.host,
    port: options.port,
    agent: _getAgent(options.host, options.port, options.https || this.target.https),
    method: req.method,
    path: req.url,
    headers: req.headers
  };
  
  protocol = _getProtocol(options.https || this.target.https, outgoing);
  

Open new HTTP request to internal resource with will act as a reverse proxy pass

  reverseProxy = protocol.request(outgoing, function (response) {
    

Process the reverseProxy response when it's received.

    if (response.headers.connection) {
      if (req.headers.connection) response.headers.connection = req.headers.connection;
      else response.headers.connection = 'close';
    }

Set the headers of the client response

    res.writeHead(response.statusCode, response.headers);

response.statusCode === 304: No 'data' event and no 'end'

    if (response.statusCode === 304) {
      return res.end();
    }

For each data chunk received from the reverseProxy response write it to the outgoing res.

    response.on('data', function (chunk) {
      if (req.method !== 'HEAD') {
        res.write(chunk);
      }
    });

When the reverseProxy response ends, end the corresponding outgoing res unless we have entered an error state. In which case, assume res.end() has already been called and the 'error' event listener removed.

    response.on('end', function () {
      if (!errState) {
        reverseProxy.removeListener('error', proxyError);
        res.end();
        

Emit the end event now that we have completed proxying

        self.emit('end', req, res);
      }
    });
  });
  

Handle 'error' events from the reverseProxy.

  reverseProxy.once('error', proxyError);
  

For each data chunk received from the incoming req write it to the reverseProxy request.

  req.on('data', function (chunk) {
    if (!errState) {
      reverseProxy.write(chunk);
    }
  });

When the incoming req ends, end the corresponding reverseProxy request unless we have entered an error state.

  req.on('end', function () {
    if (!errState) {
      reverseProxy.end();
    }
  });

If we have been passed buffered data, resume it.

  if (options.buffer && !errState) {
    options.buffer.resume();
  }
};
  

@private function _forwardRequest (req)

@req {ServerRequest} Incoming HTTP Request to proxy.

Forwards the specified req to the location specified by this.forward ignoring errors and the subsequent response.

HttpProxy.prototype._forwardRequest = function (req) {
  var self = this, port, host, outgoing, protocol, forwardProxy;

  port = this.forward.port;
  host = this.forward.host;
  
  outgoing = {
    host: host,
    port: port,
    agent: _getAgent(host, port, this.forward.https),
    method: req.method,
    path: req.url,
    headers: req.headers
  };
  

Force the connection header to be 'close' until node.js core re-implements 'keep-alive'.

  outgoing.headers['connection'] = 'close';
  
  protocol = _getProtocol(this.forward.https, outgoing);
  

Open new HTTP request to internal resource with will act as a reverse proxy pass

  forwardProxy = protocol.request(outgoing, function (response) {

Ignore the response from the forward proxy since this is a 'fire-and-forget' proxy. Remark (indexzero): We will eventually emit a 'forward' event here for performance tuning.

  });
  

Add a listener for the connection timeout event.

Remark: Ignoring this error in the event forward target doesn't exist.

  forwardProxy.once('error', function (err) { });

Chunk the client request body as chunks from the proxied request come in

  req.on('data', function (chunk) {
    forwardProxy.write(chunk);
  })

At the end of the client request, we are going to stop the proxied request

  req.on('end', function () {
    forwardProxy.end();
  });
};

function proxyWebSocketRequest (req, socket, head, options)

@req {ServerRequest} Websocket request to proxy.

@socket {net.Socket} Socket for the underlying HTTP request

@head {string} Headers for the Websocket request.

@options {Object} Options to use when proxying this request.

options.port {number} Port to use on the proxy target host.
options.host {string} Host of the proxy target.
options.buffer {Object} Result from `httpProxy.buffer(req)`
options.https {Object|boolean} Settings for https.
HttpProxy.prototype.proxyWebSocketRequest = function (req, socket, head, options) {
  var self      = this, 
      listeners = {},
      errState  = false, 
      CRLF      = '\r\n',
      outgoing;

WebSocket requests must have the GET method and the upgrade:websocket header

  if (req.method !== 'GET' || req.headers.upgrade.toLowerCase() !== 'websocket') {

This request is not WebSocket request

    return;
  }
  

Helper function for setting appropriate socket values: 1. Turn of all bufferings 2. For server set KeepAlive 3. For client set encoding

  function _socket(socket, keepAlive) {
    socket.setTimeout(0);
    socket.setNoDelay(true);
    if (keepAlive) {
      if (socket.setKeepAlive) {
        socket.setKeepAlive(true, 0);
      }
      else if (socket.pair.cleartext.socket.setKeepAlive) {
        socket.pair.cleartext.socket.setKeepAlive(true, 0);
      }
    } 
    else {
      socket.setEncoding('utf8');
    }
  }
  

On upgrade from the Agent socket, listen to the appropriate events.

  function onUpgrade (reverseProxy, proxySocket) {
    if (!reverseProxy) {
      proxySocket.end();
      socket.end();
      return;
    }
    

Any incoming data on this WebSocket to the proxy target will be written to the reverseProxy socket.

    proxySocket.on('data', listeners.onIncoming = function (data) {
      if (reverseProxy.incoming.socket.writable) {
        try {
          self.emit('websocket:outgoing', req, socket, head, data);
          reverseProxy.incoming.socket.write(data);
        } 
        catch (e) {
          reverseProxy.incoming.socket.end();
          proxySocket.end();
        }
      }
    });

Any outgoing data on this Websocket from the proxy target will be written to the proxySocket socket.

    reverseProxy.incoming.socket.on('data', listeners.onOutgoing = function(data) {
      try {
        self.emit('websocket:incoming', reverseProxy, reverseProxy.incoming, head, data);
        proxySocket.write(data);
      } 
      catch (e) {
        proxySocket.end();
        socket.end();
      }
    });
    

Helper function to detach all event listeners from reverseProxy and proxySocket.

    function detach() {
      proxySocket.removeListener('end', listeners.onIncomingClose);
      proxySocket.removeListener('data', listeners.onIncoming);
      reverseProxy.incoming.socket.removeListener('end', listeners.onOutgoingClose);
      reverseProxy.incoming.socket.removeListener('data', listeners.onOutgoing);
    }

If the incoming proxySocket socket closes, then detach all event listeners.

    proxySocket.on('end', listeners.onIncomingClose = function() {
      reverseProxy.incoming.socket.end();
      detach();
      

Emit the end event now that we have completed proxying

      self.emit('websocket:end', req, socket, head);
    });

If the reverseProxy socket closes, then detach all event listeners.

    reverseProxy.incoming.socket.on('end', listeners.onOutgoingClose = function() {
      proxySocket.end();
      detach();
    });
  };

Setup the incoming client socket.

  _socket(socket);
  
  function getPort (port) {
    port = port || 80;
    return port - 80 === 0 ? '' : ':' + port
  }
  

Get the protocol, and host for this request and create an instance of http.Agent or https.Agent from the pool managed by node-http-proxy.

  var protocolName = options.https || this.target.https ? 'https' : 'http',
      portUri      = getPort(this.source.port),
      remoteHost   = options.host + portUri,
      agent        = _getAgent(options.host, options.port, options.https || this.target.https);

Change headers (if requested).

  if (this.changeOrigin) {
    req.headers.host   = remoteHost;
    req.headers.origin = protocolName + '://' + remoteHost;
  }
  

Make the outgoing WebSocket request

  outgoing = {
    host: options.host,
    port: options.port,
    method: 'GET',
    path: req.url,
    headers: req.headers,
  };
  var reverseProxy = agent.appendMessage(outgoing);

On any errors from the reverseProxy emit the webSocketProxyError and close the appropriate connections.

  function proxyError (err) {
    reverseProxy.end();
    if (self.emit('webSocketProxyError', req, socket, head)) {
      return;
    }
    
    socket.end();
  }

Here we set the incoming req, socket and head data to the outgoing request so that we can reuse this data later on in the closure scope available to the upgrade event. This bookkeeping is not tracked anywhere in nodejs core and is very specific to proxying WebSockets.

  reverseProxy.agent = agent;
  reverseProxy.incoming = {
    request: req,
    socket: socket,
    head: head
  };
  

If the agent for this particular host and port combination is not already listening for the upgrade event, then do so once. This will force us not to disconnect.

In addition, it's important to note the closure scope here. Since there is no mapping of the

  if (!agent._events || agent._events['upgrade'].length === 0) {
    agent.on('upgrade', function (_, remoteSocket, head) {

Prepare the socket for the reverseProxy request and begin to stream data between the two sockets. Here it is important to note that remoteSocket._httpMessage === reverseProxy.

      _socket(remoteSocket, true);
      onUpgrade(remoteSocket._httpMessage, remoteSocket);
    });
  }
  

If the reverseProxy connection has an underlying socket, then execute the WebSocket handshake.

  if (typeof reverseProxy.socket !== 'undefined') {
    reverseProxy.socket.on('data', function handshake (data) {

Ok, kind of harmfull part of code. Socket.IO sends a hash at the end of handshake if protocol === 76, but we need to replace 'host' and 'origin' in response so we split data to printable data and to non-printable. (Non-printable will come after double-CRLF).

      var sdata = data.toString();

Get the Printable data

      sdata = sdata.substr(0, sdata.search(CRLF + CRLF));

Get the Non-Printable data

      data = data.slice(Buffer.byteLength(sdata), data.length);
      
      if (self.https && !self.target.https) {

If the proxy server is running HTTPS but the client is running HTTP then replace ws with wss in the data sent back to the client.

        sdata = sdata.replace('ws:', 'wss:');
      }

      try {

Write the printable and non-printable data to the socket from the original incoming request.

        self.emit('websocket:handshake', req, socket, head, sdata, data);
        socket.write(sdata);
        socket.write(data);
      } 
      catch (ex) {
        proxyError(ex)
      }

Catch socket errors

      socket.on('error', proxyError);

Remove data listener now that the 'handshake' is complete

      reverseProxy.socket.removeListener('data', handshake);
    });
  }
  
  reverseProxy.on('error', proxyError);

  try {

Attempt to write the upgrade-head to the reverseProxy request.

    reverseProxy.write(head);
  } 
  catch (ex) {
    proxyError(ex);
  }
  

If we have been passed buffered data, resume it.

  if (options.buffer && !errState) {
    options.buffer.resume();
  }
};