FriendlyUUID

FriendlyUUID is a Rails gem that shortens your UUID records' URLs.

What once was

twos.dev/users/758d633c-61d4-4dfc-ba52-b7b498971097

becomes

twos.dev/users/758d

FriendlyUUID does not introduce any new state to your models, even under the hood.

FriendlyUUID URLs are exactly as unique as they need to be. The first record will be one character. Would-be collisions expand to two characters, and so on.

FriendlyUUID is inspired by norman/friendly_id, but is focused on being lightweight and specific to models with UUID primary keys.

This project is dual-licensed under Creative Commons BY-NC-SA 4.0 and Licenseland. You can choose which to use; in general hobbyists will use Creative Commons and commercial users use a paid license through Licenseland. If you are in education, climate change, or humanitarian efforts feel free to email me and I will waive the Licenseland fee.

Add it to your Gemfile:

gem 'friendly_uuid'

Then include it in any model that has UUID primary keys:

class User < ApplicationRecord
  include FriendlyUUID
  # ...
end

And you're done! URL helpers will automatically generate shorter URLs and your model's find and find_by methods will behave as expected when given short UUIDs.

The core idea of FriendlyUUID is to truncate UUIDs until they are the shortest possible unique string.

However this approach has some nuance, demonstrated by the following operations:

1. Create record A with UUID abcdefg (shortened to a)
2. Create record B with UUID abcabca (shortened to abca)

After step 1, record A has a URL like twos.dev/users/a. After step 2, that same record has a URL like twos.dev/users/abcd. This causes two problems:

• A's URL has changed! But cool URLs don't change.
• Where should twos.dev/users/a lead now?

To address this nuance, FriendlyUUID truncates URLs past uniqueness. It keeps truncating characters as long as the URL remains the eldest among its collisions.

In other words, after the above example, A's URL continues to be twos.dev/users/a, because when its UUID is truncated to a it remains the eldest of all records whose UUIDs start with a.

And when twos.dev/users/a is accessed, FriendlyUUID knows that the record being asked for is the eldest record that starts with a.

With this tweak, records always have the shortest possible URL, their URLs never change, and one URL always points to one record—all conventional rules about URLs are followed, and no extra state was stored!

There are two disadvantages to this approach.

1. As with many stateless algorithms, you pay in machinepower. In this case, the queries to discover the shortest-possible URL are quite expensive compared to O(1) lookups. (The query to discover a record given a URL remains cheap.)

2. Deleting record A in the above example will cause twos.dev/users/a to point to B, rather than to 404 as a user might expect. You can work around this by choosing to soft-delete records whenever you would normally hard-delete them.

There are a few of reasons you might want to use UUIDs as primary keys over numeric IDs.

Using auto-incrementing numeric IDs means anyone can discover roughly how many users/articles/customers/etc. you have.

Even if you replace URL IDs with something else you are probably still leaking IDs without realizing it, as many Rails constructs (e.g. form_with) will insert IDs into your HTML.

IDs serve an important role and you should not feel afraid of using them anywhere. But with auto-incrementing numeric IDs you could be inadvertently sharing information about e.g. the success of a product to a competitor or bad actor.

When using numeric IDs in distributed systems, you may have several layers of services waiting on the ID-generating service to finish before they can act further on it, such as waiting on a user object to be created before they update another service with details about the user.

When using UUIDs the consuming service can generate the UUID itself, and simultaneously tell all the appropriate services the relevant details about it. This does not depend on one service to finish creating the record first, therefore the creation is faster and resilient to partial outages.

When using numeric IDs, each ID must be exactly the previous ID plus 1. If the ID-generating service has very high throughput, performing this operation in a concurrent-safe way can become a bottleneck, as each request must wait for all previous requests to be served.

When using UUIDs, ID generation can be parallelized as no one request depends on any previous request's state.

Existing links that use full UUIDs will not be broken. Because of the algorithm FriendlyUUID uses to lengthen shortened UUIDs, a full-length UUID is still considered a valid shortening of itself.

This means that after installing FriendlyUUID, each resource may have multiple valid URLs. Rails URL helpers will behave correctly and always return the same canonical short URL, but if there are full-form links in the wild (like on Twitter) that you want to be canonicalized you can optionally decide to forward them:

class UsersController < ApplicationController
  before_action :canonicalize_path, only: [:show, :edit]

  # ...

  private

  def canonicalize_path
    canonical_path = user_path(@user)
    redirect_to canonical_path if canonical_path != request.fullpath
  end
end

Whether or not you take this step, no links will be broken by adding FriendlyUUID to your app.

See CONTRIBUTING.md