Ruby on Rails 8.1 Release Notes

Highlights in Rails 8.1:

Active Job Continuations.
Structured Event Reporting.
Local CI.
Markdown Rendering.
Command-line Credentials Fetching.
Deprecated Associations.
Registry-Free Kamal Deployments

These release notes cover only the major changes. To learn about various bug fixes and changes, please refer to the changelogs or check out the list of commits in the main Rails repository on GitHub.

1. Upgrading to Rails 8.1

If you're upgrading an existing application, it's a great idea to have good test coverage before going in. You should also first upgrade to Rails 8.0 in case you haven't and make sure your application still runs as expected before attempting an update to Rails 8.1. A list of things to watch out for when upgrading is available in the Upgrading Ruby on Rails guide.

2. Major Features

2.1. Active Job Continuations

Long-running jobs can now be broken into discrete steps that allow execution to continue from the last completed step rather than the beginning after a restart. This is especially helpful when doing deploys with Kamal, which will only give job-running containers thirty seconds to shut down by default.

Example:

class ProcessImportJob < ApplicationJob
  include ActiveJob::Continuable

  def perform(import_id)
    @import = Import.find(import_id)

    # block format
    step :initialize do
      @import.initialize
    end

    # step with cursor, the cursor is saved when the job is interrupted
    step :process do |step|
      @import.records.find_each(start: step.cursor) do |record|
        record.process
        step.advance! from: record.id
      end
    end

    # method format
    step :finalize
  end

  private
    def finalize
      @import.finalize
    end
end

2.2. Structured Event Reporting

The default logger in Rails is great for human consumption, but less ideal for post-processing. The new Event Reporter provides a unified interface for producing structured events in Rails applications:

Rails.event.notify("user.signup", user_id: 123, email: "user@example.com")

It supports adding tags to events:

Rails.event.tagged("graphql") do
  # Event includes tags: { graphql: true }
  Rails.event.notify("user.signup", user_id: 123, email: "user@example.com")
end

As well as context:

# All events will contain context: {request_id: "abc123", shop_id: 456}
Rails.event.set_context(request_id: "abc123", shop_id: 456)

Events are emitted to subscribers. Applications register subscribers to control how events are serialized and emitted. Subscribers must implement an #emit method, which receives the event hash:

class LogSubscriber
  def emit(event)
    payload = event[:payload].map { |key, value| "#{key}=#{value}" }.join(" ")
    source_location = event[:source_location]
    log = "[#{event[:name]}] #{payload} at #{source_location[:filepath]}:#{source_location[:lineno]}"
    Rails.logger.info(log)
  end
end

2.3. Local CI

Developer machines have gotten incredibly quick with loads of cores, which make them great local runners of even relatively large test suites.

This makes getting rid of a cloud-setup for all of CI not just feasible but desirable for many small-to-mid-sized applications, and Rails has therefore added a default CI declaration DSL, which is defined in config/ci.rb and run by bin/ci. It looks like this:

CI.run do
  step "Setup", "bin/setup --skip-server"
  step "Style: Ruby", "bin/rubocop"

  step "Security: Gem audit", "bin/bundler-audit"
  step "Security: Importmap vulnerability audit", "bin/importmap audit"
  step "Security: Brakeman code analysis", "bin/brakeman --quiet --no-pager --exit-on-warn --exit-on-error"
  step "Tests: Rails", "bin/rails test"
  step "Tests: Seeds", "env RAILS_ENV=test bin/rails db:seed:replant"

  # Requires the `gh` CLI and `gh extension install basecamp/gh-signoff`.
  if success?
    step "Signoff: All systems go. Ready for merge and deploy.", "gh signoff"
  else
    failure "Signoff: CI failed. Do not merge or deploy.", "Fix the issues and try again."
  end
end

The optional integration with gh ensures that PRs must be signed off by a passing CI run in order to be eligible to be merged.

2.4. Markdown Rendering

Markdown has become the lingua franca of AI, and Rails has embraced this adoption by making it easier to respond to markdown requests and render them directly:

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

2.5. Command-line Credentials Fetching

Kamal can now easily grab its secrets from the encrypted Rails credentials store for deploys. This makes it a low-fi alternative to external secret stores that only needs the master key available to work:

# .kamal/secrets
KAMAL_REGISTRY_PASSWORD=$(rails credentials:fetch kamal.registry_password)

2.6. Deprecated Associations

Active Record associations can now be marked as being deprecated:

class Author < ApplicationRecord
  has_many :posts, deprecated: true
end

With that, usage of the posts association will be reported. This includes explicit API calls like

author.posts
author.posts = ...

and others, as well as indirect usage like

author.preload(:posts)

usage via nested attributes, and more.

Three reporting modes are supported (:warn, :raise, and :notify), and backtraces can be enabled or disabled, though you always get the location of the reported usage regardless. Defaults are :warn mode and disabled backtraces.

2.7. Registry-Free Kamal Deployments

Kamal no longer needs a remote registry, like Docker Hub or GHCR, to do basic deploys. By default, Kamal 2.8 will now use a local registry for simple deploys. For large-scale deploys, you'll still want to use a remote registry, but this makes it easier to get started and see your first Hello World deployment in the wild.

3. Railties

Please refer to the Changelog for detailed changes.

3.1. Removals

Remove deprecated rails/console/methods.rb file.
Remove deprecated bin/rake stats command.
Remove deprecated STATS_DIRECTORIES.

ActionDispatch::ParamBuilder.from_query_string("[foo]=bar") # => { "foo" => "bar" }
ActionDispatch::ParamBuilder.from_query_string("[foo][bar]=baz") # => { "foo" => { "bar" => "baz" } }

After:

ActionDispatch::ParamBuilder.from_query_string("[foo]=bar") # => { "[foo]" => "bar" }
ActionDispatch::ParamBuilder.from_query_string("[foo][bar]=baz") # => { "[foo]" => { "bar" => "baz" } }

Remove deprecated support for using semicolons as a query string separator.

Before:

ActionDispatch::QueryParser.each_pair("foo=bar;baz=quux").to_a
# => [["foo", "bar"], ["baz", "quux"]]

After:

ActionDispatch::QueryParser.each_pair("foo=bar;baz=quux").to_a
# => [["foo", "bar;baz=quux"]]

Remove deprecated support to a route to multiple paths.

5.2. Deprecations

Deprecate Rails.application.config.action_dispatch.ignore_leading_brackets.

5.3. Notable changes

Redirects are now verbose in development for new Rails apps. To enable it in an existing app, add config.action_dispatch.verbose_redirect_logs = true to your config/development.rb file.

Remove deprecated :retries option for the SQLite3 adapter.
Remove deprecated :unsigned_float and :unsigned_decimal column methods for MySQL.

8.2. Deprecations

Deprecate using an order dependent finder method (e.g. #first) without an order.
Deprecate ActiveRecord::Base.signed_id_verifier_secret in favor of Rails.application.message_verifiers (or Model.signed_id_verifier if the secret is specific to a model).
Deprecate using insert_all/upsert_all with unpersisted records in associations.
Deprecate usage of WITH, WITH RECURSIVE and DISTINCT with update_all.

8.3. Notable changes

The table columns inside schema.rb are now sorted alphabetically.

9. Active Storage

Please refer to the Changelog for detailed changes.

9.1. Removals

Remove deprecated :azure storage service.

Remove deprecated passing a Time object to Time#since.
Remove deprecated Benchmark.ms method. It is now defined in the benchmark gem.
Remove deprecated addition for Time instances with ActiveSupport::TimeWithZone.
Remove deprecated support for to_time to preserve the system local time. It will now always preserve the receiver timezone.

11.2. Deprecations

Deprecate config.active_support.to_time_preserves_timezone.
Deprecate String#mb_chars and ActiveSupport::Multibyte::Chars.
Deprecate ActiveSupport::Configurable.

Remove support to set ActiveJob::Base.enqueue_after_transaction_commit to :never, :always and :default.
Remove deprecated Rails.application.config.active_job.enqueue_after_transaction_commit.
Remove deprecated internal SuckerPunch adapter in favor of the adapter included with the sucker_punch gem.

12.2. Deprecations

Custom Active Job serializers must have a public #klass method.
Deprecate built-in sidekiq adapter (now provided by sidekiq gem).