Refreshing my Rails: OmniAuth

I’m refreshing my understanding of mainstay Rails libraries lately¹. This week, it’s OmniAuth.

When you sign-in (authenticate) to website A (say dev.to) via website B (say GitHub), that’s delegated authentication and the protocol underneath it is OAuth2. OAuth2 is a bit tricky because there is a lot of back-and-forth between the service that the user signs into (GitHub) and the service that you’re signing into with that authentication (dev.to).

Once you’ve set it up set it up, OmniAuth encapsulates much of the back-and-forth with a Strategy class. A bunch of folks out on the internet have bravely contributed literally hundreds of strategies for various services that provide OAuth2 sign-in, e.g. omniauth-twitter or omniauth-github.

A nice thing about the Strategy implementation is that each phase of the OAuth2 callback scheme² is a method; you can overwrite each one to handle the particularities of the provider you’re integrating with. For example, the “callback phase” is the most common extension point since every app is likely to want to store user information and access tokens differently.

In the wild, OmniAuth is often used in combination with Devise for user models which in turn uses Warden for authentication.

Also nifty to note: the Rakefile for OmniAuth has developer tasks for benchmarking performance and measuring memory overhead. It’s pretty awesome that an essential gem like this has that level of detail in its maintenance.

The time required to do a simplistic OAuth verification is negligible; about as fast as a call to Redis:

% rake perf:ips
Warming up --------------------------------------
                 ips     1.210k i/100ms
Calculating -------------------------------------
                 ips     12.329k (± 5.1%) i/s -     61.710k in   5.019465s

I have no baseline to compare this with, but memory usage looks like this:

% rake perf:mem|head
Total allocated: 147317 bytes (831 objects)
Total retained:  60863 bytes (152 objects)

allocated memory by gem
-----------------------------------
     74492  lib
     52894  rubygems
     12659  omniauth/lib
      4200  rack-2.0.7
      2832  hashie-3.6.0

So that’s OmniAuth. If your Rails app is more than a few years old and integrates with other services, you’re probably already using it. Thanks, OmniAuth community!