middler

An embeddable middleware runner

npm install middler
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middler

An embeddable middleware runner

Build Status

Idea

middler is a flexible, tiny middleware runner for Node.js which can easily be embedded in an existing http server or even an existing middleware chain. Also provided is express-like routing and union compatibility. Best of all, the code is readable, compact, tested, benchmarked, and MIT-licensed.

Enjoy!

Install

$ npm install --save middler

Basic usage

var middler = require('middler')
  , server = require('http').createServer()

// to attach a single handler to the server:
middler(server, function (req, res, next) {
  console.log(req.method, req.url);
  next();
});

// calling middler(server) again will access the same middleware chain:
middler(server)
  // note: all methods are chainable!
  .get('/', function(req, res, next) {
    res.writeHead(200, {'Content-Type': 'text/plain'});
    res.end('hello world!');
  })
  // since this handler is added last, it will run last:
  .add(function (req, res, next) {
    res.writeHead(404, {'Content-Type': 'text/plain'});
    res.end('page not found...');
  })

server.listen(3000);

HTTP Routing

It's easy to set up routes which will respond to certain methods and paths:

middler(server)
  .add('/', function (req, res, next) {
    // handle any request to "/" path
  })
  .get('/robots.txt', function (req, res, next) {
    // handle GET requests only
    res.end('humans only!');
  })
  .first('/posts/*', function (req, res, next) {
    // do some setup for any path starting with '/posts/'
    next();
  })
  .post('/posts/:id', function (req, res, next) {
    // req.params.id available
  })
  .put('/articles/*/*', function (req, res, next) {
    // req.params is an array with 2 elements
  })
  .get('*.mydomain.com', '/', function (req, res, next) {
    // vhost matcher: handle the root path on *.mydomain.com
  })
  .add('localhost', function (req, res, next) {
    // vhost matcher: only handle requests to localhost
  })

Tips:

  • Paths must be either strings starting with /, or RexExp objects.
  • Other methods available: delete, head, patch

middler is a middleware, too

Now, the coolest feature of middler which sets it apart from the rest: embeddability.

Each middler instance has a handler property which allows you to use the entire chain as a single middleware handler!

Example with connect:

var connect = require('connect')
  , http = require('http')
  , middler = require('middler')

var app = connect()
  .use(connect.favicon())
  .use(connect.logger('dev'))
  .use(connect.static('public'))
  .use(connect.directory('public'))
  .use(connect.cookieParser('my secret here'))
  .use(connect.session())
  .use(middler()
    .get('/', function (req, res, next) {
      res.end('hello world!');
    })
    .add(function (req, res) {
      res.writeHead(404);
      res.end('page not found');
    })
    .handler
  );

http.createServer(app).listen(3000);

This can be extremely useful if you want to:

  • Bundle your app's features as middler chains which can be optionally attached to the main chain, similar to "controllers" in MVC language.
  • Create a vhost architecture which hands off requests to a sub-chain.
  • Write node modules which provide advanced middleware (respond to a variety of methods/paths/etc), and can be attached directly to a server instance or used with connect/express/flatiron.

Stack control

To add handlers which should run first or last in the stack:

middler(server)
  .last(function (req, res, next) {
    // this should run last (weight = 1000)
  })
  .first(function (req, res, next) {
    // this should run first (weight = -1000)
  })
  .add(500, function (req, res, next) {
    // numbers become weights -- give an arbitrary weight of 500, will run in-
    // between the above handlers
  })

To remove handler(s) from the stack:

function myHandler (req, res, next) {}

middler(server)
  .add(myHandler)
  .add('/about', function (req, res, next) {
    res.end('about us');
  })
  .add(function (req, res, next) {
    res.end('page not found');
  })

// let's remove myHandler
middler(server).remove(myHandler);

// let's remove /about
middler(server).remove('/about');

// actually let's clear the whole thing
middler(server).removeAll();

Multiple paths/methods/handlers

middler(server)
  .add(['get', 'post'], '/', function (req, res, next) {
    // handle both GET and POST requests to "/"
  })

// Or add multiple handlers
function bodyParser (req, res, next) { req.body = ... }
function formHandler (req, res, next) { // do something with req.body ... }

middler(server)
  .post('/posts', [bodyParser, formHandler])
  // or even the "flat style"
  .post('/posts', '/comments', bodyParser, formHandler)

When multiple handlers are added, they execute in series when the other conditions match.

Handling errors

If your application encounters an error, pass an Error object to the next callback. The rest of the middleware chain will not run, and what middler does with the error is dependent on the following conditions:

  • If there are error event listener(s) on the middler instance, they will be invoked with err, req, res and the error will not propagate further.
  • If there is no error listener:
    • In the case of an embedded middler, the error will propagate to the parent chain, i.e. next(err).
    • Otherwise, the default error handler will run which terminates the response with 500 Internal Server Error status and no body. The error and stack trace will be printed to process.stderr.

Example custom error handler:

middler(server)
  .on('error', function (err, req, res) {
    res.writeHead(500, {'Content-Type': 'text/plain'});
    console.error(err.stack || err);
    res.end('sorry, blame it on Rackspace!');
  })
  .add(function (req, res, next) {
    // next() can accept an error
    next(new Error('whoops!'));
  })

Alternate attach syntax

var server = require('http').createServer();
var router = middler()
  .add(function (req, res, next) {
    // handle request...
  })
  .attach(server)

// you can also detach!
router.detach();

// router can be attached do a different server now

union compatibility

middler(server)
  .add(function () {
    // this.req
    // this.res
    this.res.emit('next');
  })

Benchmarks

My results: https://gist.github.com/3473117

App with single middleware, "hello world"

****************  middler (7646.63 rps)
****************  connect (7198.48 rps)
*******           union (3057.69 rps)

App with 100 routes

****************  middler-routes (6870.59 rps)
***************   express-routes (6335.41 rps)
******            director-routes (2414.89 rps)

Running your own benchmark

In the middler root, run:

$ make bench

Brought to you by benchmarx.


Developed by Terra Eclipse

Terra Eclipse, Inc. is a nationally recognized political technology and strategy firm located in Aptos, CA and Washington, D.C.

http://www.terraeclipse.com

License: MIT

Copyright (C) 2012 Terra Eclipse, Inc.

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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