Enable Ruby YJIT for performance boost 🚀

[larouxn]

Follow up to the upgrade to Ruby 3.3.0, which brought with a much improved YJIT, this PR actually enables said YJIT for a supposed free performance boost of around 15%-25% latency wise.

• Upgrade from Ruby 3.2.2 to Ruby 3.3.0 #2110

Caveat being devdocs isn't a Rails codebase nor is it a massive app but regardless, this should be a free performance win with little to no possible downsides assuming devdocs is not running with minimal RAM. For further reference, here is a blog post on the performance increase, as well as PR that made YJIT easily enable-able for Rails on Ruby 3.3+.

• https://railsatscale.com/2023-12-04-ruby-3-3-s-yjit-faster-while-using-less-memory/
• Enable YJIT by default if running Ruby 3.3+ rails/rails#49947

As for the approach, I don't know a whole lot about Dockerfiles nor setting arbitrary env vars but I followed the following two guides/posts on how to enable YJIT, as they seem legitimate, having uses fly.io before myself.

• https://mailsnag.com/blog/optimized-ruby-dockerfile/
• https://fly.io/docs/rails/cookbooks/deploy/#yjit

[simon04]

Hi, the Docker files are provided only for people who want to self-host. The main instance devdocs.io is running on Heroku and is being deployed via .github/workflows/build.yml – do you think it's worth investigating/enabling YJIT on Heroku?

(@ojeytonwilliams, fyi)

[larouxn]

Ah, understood. It looks like all we need to do to enable YJIT on Heroku is set the variable, according to the docs.

heroku config:set RUBYOPT="--enable-yjit"

I suppose we can close this PR unless we want to recommend enabling YJIT by default, which seems reasonable.

[larouxn]

Closing this as the change can be made at the application level re: #2127 (comment).