Rails World starts tomorrow and that could mean an alpha of Rails 8.0. But you don’t need to wait, you can try it out today:
rails new rails8 --main
cd rails8
echo 'Rails.application.routes.draw { root "rails/welcome#index" }' >> config/routes.rb
fly launch
Two changes were made to enable this to work. A third set of changes are being investigated.
1. only create sidekiq or solid queue processes if jobs are defined
Previously if either of these gems were installed that was taken as a clear indication that jobs were going to be performed and a process was set up to handle this task. With Rails 8, solid queue is installed by default so that no longer is true. A change was made to actually look for jobs being defined in the app/jobs/*.rb directory before creating this process.
2. Enable DATABASE_URL to control the placement of all of the databases
Previously, a single Rails application would have only one database by default. With Rails 8, a default application will have four databases. Conceivably, they all could be placed in different places, but in practice you will want to place them all together. A small change to your config/database.yml file will be made at fly launch time to enable a single DATABASE_URL secret to control the placement of all four databases. Brainstorming is under way to explore ways that Rails 8 can handle this case better.
3. Adopt features from the default Dockerfile that Rails produces into dockerfile-rails.
As an example, dockerfile rails has always supported jemalloc as an option. Rails now includes this by default. dockerfile rails will be updated to also default this to true, even when launching applications based on prior versions of Rails.
Meanwhile, fly.io has been tested with both the Rails provided Dockerfiles and the docker files produced by the dockerfile generator.