distribute

Load balancer / proxy / router organized around Express/Connect-like middleware.

npm install distribute
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Distribute

Distribute is a middleware-based API to expressively perform request routing / load balancing in Node.JS.

How to use

Normal HTTP

var http = require('http').createServer().listen(3000)
  , srv = require('balance')(http);

srv.use(function (req, res, next) {
  if (req.headers.host == 'blog.mydomain.com') {
    next(8000);
  } else {
    next();
  }
});

srv.use(function (req, res, next) {
  somethingAsync(function (err, host, port) {
    if (err) return next(err); // sends a `500` and cleans up
    next(port, host);
  });
});

WebSocket

Requests triggered by the upgrade event (as a result of the Upgrade HTTP header) are handled by prepending the ws flag each time you call use.

server.ws.use(function (req, socket, next) {
  next(3000);
});

Features

  • Leverages the well-tested node-http-proxy.
  • Simplicity of Express.
  • Compatible with connect middleware (eg: qs parser, cookie decoder).
  • Middleware makes sticky/session load balancing trivial to write.
  • Middleware can perform async tasks. Distribute manages buffers transparently for you.

API

next

The next parameter can take three signatures:

  • no parameters (next()) will execute the next middleware. If no middleware is available, an error is displayed (refer to the "Default behaviors section")
  • port (Number)
  • port (Number), host (String)

req

Distribute adds two properties to request objects:

req.buf

The node-http-proxy data buffer.

req.head

For WS requests, the first packet of the stream, only present for legacy purposes.

Behaviors

Error handling

When an Error object is passed to next, or when no middleware will handle a given request, the default behavior is to show a 500 Internal Server Error (for HTTP requests) or the socket is ended (WS requests). In development (ie: NODE_ENV is set to development), a stack trace is sent along with the error code.

If you want to define custom "error handling middleware", you can do so by adding a function with 4 parameters instead of 3 (in other words, with an arity of 4).

// regular requests
srv.use(function (err, req, res, next) {
  next();
});

// ws requests
srv.use(function (err, req, socket, next) {
  next();
});

It's not necessary to pass the error to next to trigger the next error middleware.

Buffers

Request data buffers are cleaned up automatically when:

  • a response is produced prematurely instead of proxying. For example

    srv.use(function (req, res, next) {
    res.writeHead(204);
    res.end();
    });
    
  • a socket for an upgrade is .end or .destroy prematurely:

    srv.ws.use(function (req, socket, next) {
    socket.end();
    });
    

License

(The MIT License)

Copyright (c) 2011 Guillermo Rauch <guillermo@learnboost.com>

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.

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