Rendering Markdown is real, plus new database connection pool options

Hi, it’s zzak. Let’s explore this week’s changes in the Rails codebase.

Rails 8.1 Beta 1 lands
The first beta release was cut for Rails 8.1, see the post for full details.

Rails World 2025 Opening Keynote
Part of the newsletter team is enjoying Rails World in Amsterdam, say hi to them if you attend. If you (like me) couldn’t go, the first keynote is already up!

Introduce new database configuration options for managing connection pools

This PR adds keepalive, max_age, and min_connections – and renames pool to max_connections to match. There are no changes to default behavior, but these allow for more specific control over pool behavior.

Move “LIMIT” validation from query generation to when “limit()” is called.
While part of Arel’s private API, the removal of sanitize_limit is possibly worth noting here.

Add markdown mime type and renderer
Add .md/.markdown as Markdown extensions and add a default "markdown:" renderer:

class Page
  def to_markdown
    body
  end
end

class PagesController < ActionController::Base
  def show
    @page = Page.find(params[:id])

    respond_to do |format|
      format.html
      format.md { render markdown: @page }
    end
  end
end

Action Controller now raises “TooManyRequests” error from rate limiting
Requests that exceed the rate limit now raise an ActionController::TooManyRequests error. Previously this would call "head :too_many_requests", but now you can use rescue_from to handle these in your app.

Deprecate built-in Sidekiq adapter
Since the Sidekiq adapter was successfully merged upstream we no longer need to maintain it internally in Rails. If you’re using this adapter, upgrade to sidekiq 7.3.3 or later to use the sidekiq gem’s adapter.

Optimize Active Job argument serialization by ~5x
An interesting change for sure, this may impact users with a custom serializer, and maybe not set in stone.

Add namespace setter and getter to Active Support’s Cache Store
In development or after initialization a user may want to inspect the current cache namespace. They may also wish to change it. This PR adds this functionality.

Add “parallel_worker_id” helper for running parallel tests
This allows users to know which worker they are currently running in, via ActiveSupport::TestCase.parallel_worker_id.

Enable debug mode for Event Reporter in local environments
Rails will now emit debug events by default in development, and test so calls to Rails.event.debug should be visible.

You can view the whole list of changes here. We had 27 contributors to the Rails codebase this past week!

Until next time!