request-extensible

A tiny library for added extensions to Request.

npm install request-extensible

Introduction

Request is a popular HTTP client library for node.js.

Although it has a great deal of built-in functionality, there are times when you'll need additional features that aren't included by default.

Usage

Usage is probably best explained with some examples.

Logging the time taken to make a request

As an extremely simple demo, let's add logging to monitor the time taken for each request and print it to the console.

var requestExt = require('request-extensible');
var request = requestExt({
  extensions: [
    /* Each extension is a function with a signature similar to the
     * request() signature, except that a additional `next` parameter is
     * provided, which needs to be called to invoke the next middleware,
     * or the underlying request call (depending on whether this is the last
     * middleware in the chain)
     */
    function(options, callback, next) {
      var start = Date.now();

      /* Call the next middleware in the chain */
      next(options, function(err, response, body) {
        var duration = Date.now() - start;
        console.log("request: " + options.url + " took " + duration + "ms");

        /* Call `callback` to return to the caller */
        callback(err, response, body);
      });
    }
  ]
});

// Now, use request as normal...
// request({ url: ...}, function(err, response, body) { ... });

Each extension has the ability to modify the outgoing request, bypass the underlying call or modify the incoming response. Even all three in the same extension.

Bypassing the underlying HTTP(s) call

In this example, we'll bypass the underlying request if the URL for all requests made to http://example.com and simply return a string response. While this may not seem to be too useful, it can be used as the basis of an HTTP caching mechanism.

var requestExt = require('request-extensible');
var request = requestExt({
  extensions: [
    function(options, callback, next) {
      if (options.url === 'http://example.com') {
        /* Bypass the underlying call and return immediately with the static
         * response
         */
        return callback(null, { statusCode: 200 }, "This is the body");
      }

      /* Otherwise, simply call the next extension in the chain */
      return next(options, callback);
    }
  ]
});

// Now, use request as normal...
// request({ url: ...}, function(err, response, body) { ... });

Using multiple extensions

Multiple extensions can be added. Extensions are executed from first to last, with each extension calling the next level down in the chain on next.

var requestExt = require('request-extensible');
var request = requestExt({
  extensions: [
    function(options, callback, next) {
      /* Add a user-agent header */
      if (!options.headers) options.headers = { };
      options.headers['user-agent'] = 'request-extensible-demo/1.0';

      return next(options, callback);
    },
    function(options, callback, next) {
      /* Count the number of requests */
      /* Each of these requests will have the user-agent header set */
      count++;
      return next(options, callback);
    },
    function(options, callback, next) {
      /* Log all errors to the console */
      next(options, function(err, response, body) {
        if (err) {
          console.error('request: error: ', options.url, err);
        } else if (response.statusCode >= 500) {
          console.error('request: http-error: ', options.url, response.statusCode);
        }

        /* Return control up the chain */
        callback(err, response, body);
      })
    }
  ]
});

// Now, use request as normal...
// request({ url: ...}, function(err, response, body) { ... });

Note, additionally that each extension can invoke the next method multiple times, so multiple HTTP requests can be made and spliced together according to the needs of the application. Note that callback should only ever be called once.

Other uses

Other extensions could include, but are not limited to:

• Automatically fetching multiple pages of responses and returning all the pages as a single response.
• Adding authentication information
• HTTP caching using ETags and Conditional Requests.
• Monitoring rate-limiting headers
• Statistics

And more!

Available Extensions

Write your own and publish them as npm modules.

Currently, only a few are available:

Module	Description
request-http-cache	In memory or Redis-based HTTP response caching using ETags and HTTP Conditional Requests. Currently this module is specifically designed around making calls to the GitHub API and has not yet been tested or extended for general use.

Licence

License The MIT License (MIT)

Copyright (c) 2015, Andrew Newdigate

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.