Shortener¶ ↑

Shortener is a Rails Engine Gem that makes it easy to create and interpret shortened URLs on your own domain from within your Rails application. Once installed Shortener will generate, store URLS and “unshorten” shortened URLs for your applications visitors, all whilst collecting basic usage metrics.

Overview¶ ↑

The majority of the Shortener consists of three parts:

a model for storing the details of the shortened link;
a controller to accept incoming requests and redirecting them to the target URL;
a helper for generating shortened URLs from controllers and views.

Dependencies¶ ↑

Shortener is designed to work from within a Rails 3 and Rails 4 applications. It has dependancies Rails core components like ActiveRecord, ActionController, the rails routing engine and more.

Ruby Version Support¶ ↑

As Ruby 1.9.3 entered end of maintainance in early 2015, the last version of the Shortener gem to support Ruby 1.9.3 is 0.4.x. Shortener v0.5 onwards will require Ruby 2+.

Upgrading¶ ↑

v0.4.0 to v0.5.0¶ ↑

There have been some breaking changes:

The owner argument is passed into the generator and helper methods as a named parameter.
Original URLs arguments without a hypertext protocol (http|https) will be assumed to be relative paths.

v0.5.1 to v0.5.2¶ ↑

v0.5.2 introduced the ability to set an expiration date for a shortened URL. The expiration dates are stored in a expires_at column in the database, which can be added to your schema with the following migration:

class AddExpiresAtToShortenedUrl < ActiveRecord::Migration[4.2]
  def change
    add_column :shortened_urls, :expires_at, :datetime
  end
end

v0.5.6 to v0.6.1¶ ↑

v0.6.1 introduced the ability to categorize a shortened URL. The category value is stored in a string column in the database, which must be added to your schema with the following migration:

bundle exec rails g migration add_category_to_shortened_url category:string:index

class AddCategoryToShortenedUrl < ActiveRecord::Migration[4.2]
  def change
    add_column :shortened_urls, :category, :string
    add_index :shortened_urls, :category
  end
end

Some niceities of Shortener:¶ ↑

The controller does a 301 redirect, which is the recommended type of redirect for maintaining maximum google juice to the original URL;
A unique alphanumeric code of generated for each shortened link, this means that we can get more unique combinations than if we just used numbers;
The link records a count of how many times it has been “un-shortened”;
The link can be associated with a user, this allows for stats of the link usage for a particular user and other interesting things;

Future improvements:¶ ↑

There has not been an attempt to remove ambiguous characters (i.e. 1 l and capital i, or 0 and O etc.) from the unique key generated for the link. This means people might copy the link incorrectly if copying the link by hand;
The system could pre-generate unique keys in advance, avoiding the database penalty when checking that a newly generated key is unique;
The system could store/cache the shortened URL if the url is to be continually rendered;

Installation¶ ↑

Shortener is compatible with Rails v3, v4 & v5. To install, add to your Gemfile:

gem 'shortener'

After you install Shortener run the generator:

rails generate shortener

This generator will create a migration to create the shortened_urls table where your shortened URLs will be stored.

Note: The default length of the url field in the generated migration is 2083. This is because MySQL requires fixed length indicies and browsers have a defacto limit on URL length. This may not be right for you or your database. The discussion can be seen here github.com/jpmcgrath/shortener/pull/98

Then add to your routes:

get '/:id' => "shortener/shortened_urls#show"

Configuration¶ ↑

The gem can be configured in a config/initializers/shortener.rb file.

By default, the shortener will generate keys that are 5 characters long. You can change that by specifying the length of the key like so;

Shortener.unique_key_length = 6

By default, when a unique key isn’t matched the site is redirected to “/”. You can change that by specifying a different url like so;

Shortener.default_redirect = "http://www.someurl.com"

By default, Shortener will generate unique keys using numbers and lowercase a-z. If you desire more combinations, you can enable the upper and lower case charset, by including the following:

Shortener.charset = :alphanumcase

If you want to use a custom charset, you can create your own combination by creating an array of possible values, such as allowing underscore and dashes:

Shortener.charset = ("a".."z").to_a + (0..9).to_a + ["-", "_"]

If you want to use a custom charset, you can create your own combination by creating an array of possible values, such as allowing underscore and dashes:

Shortener.charset = ("a".."z").to_a + (0..9).to_a + ["-", "_"]

Usage¶ ↑

To generate a Shortened URL object for the URL “example.com” within your controller / models do the following:

Shortener::ShortenedUrl.generate("http://example.com")

Alternatively, you can create a shortened url to a relative path within your application:

Shortener::ShortenedUrl.generate("/relative-path?param=whatever")

To generate and display a shortened URL in your application use the helper method:

short_url("http://example.com")

Pass in subdomain, protocol and other options that the UrlHelper url_for accepts:

short_url("http://example.com", url_options: { subdomain: 'foo', host: 'bar', protocol: 'https' } )

This will generate a shortened URL. store it to the db and return a string representing the shortened URL.

Shortened URLs with owner¶ ↑

You can link shortened URLs to an owner, to scope them. To do so, add the following line to the models which will act as owners:

class User < ActiveRecord::Base
  has_shortened_urls
end

This will allow you to pass the owner when generating URLs:

Shortener::ShortenedUrl.generate("example.com", owner: user)

short_url("http://example.com", owner: user)

And to access those URLs:

user.shortened_urls

Shortened URLs with custom unique key¶ ↑

You can pass in your own key when generating a shortened URL. This should be unique.

Important: Custom keys can’t contain characters other than those defined in Shortener.charset. Default is numbers and lowercase a-z (See Configuration).

Shortener::ShortenedUrl.generate("example.com", owner: user, custom_key: "mykey")

short_url("http://example.com", custom_key: 'yourkey')

Expirable Shortened URLs¶ ↑

You can create expirable URLs. Probably, most of the time it would be used with owner:

Shortener::ShortenedUrl.generate("example.com/page", user, expires_at: 24.hours.since)

You can omit owner passing nil instead:

Shortener::ShortenedUrl.generate("example.com/page", nil, expires_at: 24.hours.since)

Fresh Links¶ ↑

Sometimes you just need that feeling of a fresh, untouched Shortened URL. By default, Shortener will find an existing ShortenedUrl record for a supplied URL. If you want to create a fresh record, you can pass the following argument:

Shortener::ShortenedUrl.generate("example.com/page", fresh: true)
short_url("http://example.com", fresh: true)

Forbidden keys¶ ↑

You can ensure that records with forbidden keys will not be generated. In rails you can put next line into config/initializers/shortener.rb

Shortener.forbidden_keys.concat %w(terms promo)

Ignoring Robots¶ ↑

By default Shortener will count all visits to a shortened url, including any crawler robots like the Google Web Crawler, or Twitter’s link unshortening bot. To ignore these visits, Shortener makes use of the excellent voight_kampff gem to identify web robots. This feature is disabled by default. To enable add the following to your shortener configuration:

Shortener.ignore_robots = true

Mounting on a Subdomain¶ ↑

If you want to constrain the shortener route to a subdomain, the following config will prevent the subdomain parameter from leaking in to shortened URLs if it matches the configured subdomain.

Within config/initializers/shortener.rb

Shortener.subdomain = 's'

Within config/routes.rb

constraints subdomain: 's' do
  get '/:id' => "shortener/shortened_urls#show"
end

URL Parameters¶ ↑

Parameters are passed though from the shortened url, to the destination URL. If the destination URL has the same parameters as the destination URL, the parameters on the shortened url take precedence over those on the destination URL.

For example, if we have an orginal URL of: > destination.com?test=yes&happy=defo (identified with token ABCDEF) Which is shortened into: > coolapp.io/s/ABCDEF?test=no&why=not Then, the resulting URL will be: >destination.com?test=no&happy=defo&why=not Note how the test parameter takes the value given on the short URL.

Shorten URLs in generated emails¶ ↑

You can register the included mail interceptor to shorten all links in the emails generated by your Rails app. For example, add to your mailer:

class MyMailer < ActionMailer::Base
  register_interceptor Shortener::ShortenUrlInterceptor.new
end

This will replace all long URLs in the emails generated by MyMailer with shortened versions. The base URL for the shortener will be infered from the mailer’s default_url_options. If you use a different hostname for your shortener, you can use:

class MyMailer < ActionMailer::Base
  register_interceptor Shortener::ShortenUrlInterceptor.new :base_url => "http://shortener.host"
end

The interceptor supports a few more arguments, see the implementation for details.

Logging, stats and other tricks¶ ↑

If you want more things to happen when a user accesses one of your short urls, you can create your own ‘show` action as follows:

def show
  token = ::Shortener::ShortenedUrl.extract_token(params[:id])
  url   = ::Shortener::ShortenedUrl.fetch_with_token(token: token, additional_params: params)
  # do some logging, store some stats
  redirect_to url[:url], status: :moved_permanently
end

Fetch with Token¶ ↑

The `::Shortener::ShortenedUrl.fetch_with_token(token: token, additional_params: params)` does the following:
1. finds the ShortenedUrl for the supplied token
2. increments the use_count for the retrieved ShortenedURL
3. combines the additional parameters with the URL in the retrieved ShortenedURL
4. returns a hash of the format `{url: <the original url>, shortened_url: <the retrieved ShortenedURL>}

*note:* If no shortened URL is found, the url will be `default_redirect` or `/`

Origins¶ ↑

For a bit of backstory to Shortener see this blog post.

In The Wild¶ ↑

Shortener is used in a number of production systems, including, but not limited to:

If you are using Shortener in your project and would like to be added to this list, please get in touch!

Contributing¶ ↑

We welcome new contributors. Because we’re all busy people, and because Shortener is used/relied upon by many projects, it is essential that new Pull Requests are opened with good spec coverage, and a passing build on supported ruby versions and Rails versions.

To contribute:

Fork it
Create your feature branch (git checkout -b my-new-feature)
Write spec coverage of changes
Commit your changes (git commit -am ‘Add some feature’)
Push to the branch (git push origin my-new-feature)
Create a new Pull Request
Ensure the build is passing

Note: We adhere to the community driven Ruby style guide: github.com/bbatsov/ruby-style-guide

ben-gy/shortener