Wrap evaluation of db/seeds.rb with the executor

Before #34953, when using the `:async` Active Job queue adapter, jobs
enqueued in `db/seeds.rb`, such as Active Storage analysis jobs, would
cause a hang (see #34939).  Therefore, #34953 changed all jobs enqueued
in `db/seeds.rb` to use the `:inline` queue adapter instead.  (This
behavior was later limited to only take effect when the `:async` adapter
was configured, see #35905.)  However, inline jobs in `db/seeds.rb`
cleared `CurrentAttributes` values (see #37526).  Therefore, #37568
changed the `:inline` adapter to wrap each job in its own thread, for
isolation.  However, wrapping a job in its own thread affects which
database connection it uses.  Thus inline jobs can no longer execute
within the calling thread's database transaction, including seeing any
uncommitted changes.  Additionally, if the calling thread is not wrapped
with the executor, the inline job thread (which is wrapped with the
executor) can deadlock on the load interlock.  And when testing (with
`connection_pool.lock_thread = true`), the inline job thread can
deadlock on one of the locks added by #28083.

Therefore, this commit reverts the solutions of #34953 and #37568, and
instead wraps evaluation of `db/seeds.rb` with the executor.  This
eliminates the original hang from #34939, which was also due to running
multiple threads and not wrapping all of them with the executor.  And,
because nested calls to `executor.wrap` are ignored, any inline jobs in
`db/seeds.rb` will not clear `CurrentAttributes` values.

Alternative fix for #34939.
Reverts #34953.
Reverts #35905.
Partially reverts #35896.

Alternative fix for #37526.
Reverts #37568.

Fixes #40552.

activejob/lib/active_job/queue_adapters/inline_adapter.rb

@@ -12,7 +12,7 @@ module QueueAdapters
     #   Rails.application.config.active_job.queue_adapter = :inline
     class InlineAdapter
       def enqueue(job) #:nodoc:
-        Thread.new { Base.execute(job.serialize) }.join
+        Base.execute(job.serialize)
       end
 
       def enqueue_at(*) #:nodoc:

activejob/test/integration/queuing_test.rb

@@ -4,7 +4,6 @@
 require "jobs/logging_job"
 require "jobs/hello_job"
 require "jobs/provider_jid_job"
-require "jobs/thread_job"
 require "active_support/core_ext/numeric/time"
 
 class QueuingTest < ActiveSupport::TestCase
@@ -146,21 +145,4 @@ class QueuingTest < ActiveSupport::TestCase
     assert job_executed "#{@id}.2"
     assert job_executed_at("#{@id}.2") < job_executed_at("#{@id}.1")
   end
-
-  test "inline jobs run on separate threads" do
-    skip unless adapter_is?(:inline)
-
-    after_job_thread = Thread.new do
-      ThreadJob.latch.wait
-      assert_nil Thread.current[:job_ran]
-      assert ThreadJob.thread[:job_ran]
-      ThreadJob.test_latch.count_down
-    end
-
-    ThreadJob.perform_later
-
-    after_job_thread.join
-
-    assert_nil Thread.current[:job_ran]
-  end
 end

activejob/test/jobs/thread_job.rb

@@ -1,22 +0,0 @@
-# frozen_string_literal: true
-
-class ThreadJob < ActiveJob::Base
-  class << self
-    attr_accessor :thread
-
-    def latch
-      @latch ||= Concurrent::CountDownLatch.new
-    end
-
-    def test_latch
-      @test_latch ||= Concurrent::CountDownLatch.new
-    end
-  end
-
-  def perform
-    Thread.current[:job_ran] = true
-    self.class.thread = Thread.current
-    self.class.latch.count_down
-    self.class.test_latch.wait
-  end
-end

railties/lib/rails/engine.rb

@@ -2,6 +2,7 @@
 
 require "rails/railtie"
 require "rails/engine/railties"
+require "active_support/callbacks"
 require "active_support/core_ext/module/delegation"
 require "active_support/core_ext/object/try"
 require "pathname"
@@ -422,6 +423,9 @@ def find(path)
       end
     end
 
+    include ActiveSupport::Callbacks
+    define_callbacks :load_seed
+
     delegate :middleware, :root, :paths, to: :config
     delegate :engine_name, :isolated?, to: :class
 
@@ -559,13 +563,7 @@ def config
     # Blog::Engine.load_seed
     def load_seed
       seed_file = paths["db/seeds.rb"].existent.first
-      return unless seed_file
-
-      if config.try(:active_job)&.queue_adapter == :async
-        with_inline_jobs { load(seed_file) }
-      else
-        load(seed_file)
-      end
+      run_callbacks(:load_seed) { load(seed_file) } if seed_file
     end
 
     initializer :load_environment_config, before: :load_environment_hook, group: :all do
@@ -637,6 +635,12 @@ def load_seed
       end
     end
 
+    initializer :wrap_executor_around_load_seed do |app|
+      self.class.set_callback(:load_seed, :around) do |engine, seeds_block|
+        app.executor.wrap(&seeds_block)
+      end
+    end
+
     initializer :engines_blank_point do
       # We need this initializer so all extra initializers added in engines are
       # consistently executed after all the initializers above across all engines.
@@ -678,18 +682,6 @@ def load_config_initializer(initializer) # :doc:
         end
       end
 
-      def with_inline_jobs
-        queue_adapter = config.active_job.queue_adapter
-        ActiveSupport.on_load(:active_job) do
-          self.queue_adapter = :inline
-        end
-        yield
-      ensure
-        ActiveSupport.on_load(:active_job) do
-          self.queue_adapter = queue_adapter
-        end
-      end
-
       def has_migrations?
         paths["db/migrate"].existent.any?
       end

railties/lib/rails/railtie.rb

@@ -1,6 +1,7 @@
 # frozen_string_literal: true
 
 require "rails/initializable"
+require "active_support/descendants_tracker"
 require "active_support/inflector"
 require "active_support/core_ext/module/introspection"
 require "active_support/core_ext/module/delegation"
@@ -135,6 +136,7 @@ module Rails
   class Railtie
     autoload :Configuration, "rails/railtie/configuration"
 
+    extend ActiveSupport::DescendantsTracker
     include Initializable
 
     ABSTRACT_RAILTIES = %w(Rails::Railtie Rails::Engine Rails::Application)
@@ -144,13 +146,7 @@ class << self
       delegate :config, to: :instance
 
       def subclasses
-        @subclasses ||= []
-      end
-
-      def inherited(base)
-        unless base.abstract_railtie?
-          subclasses << base
-        end
+        super.reject(&:abstract_railtie?)
       end
 
       def rake_tasks(&blk)

railties/test/railties/engine_test.rb

@@ -879,29 +879,40 @@ def index
       assert Bukkits::Engine.config.bukkits_seeds_loaded
     end
 
-    test "jobs are ran inline while loading seeds with async adapter configured" do
+    test "loading seed data is wrapped by the executor" do
       app_file "db/seeds.rb", <<-RUBY
-        Rails.application.config.seed_queue_adapter = ActiveJob::Base.queue_adapter
+        Rails.application.config.seeding_wrapped_by_executor = Rails.application.executor.active?
       RUBY
 
       boot_rails
       Rails.application.load_seed
 
-      assert_instance_of ActiveJob::QueueAdapters::InlineAdapter, Rails.application.config.seed_queue_adapter
-      assert_instance_of ActiveJob::QueueAdapters::AsyncAdapter, ActiveJob::Base.queue_adapter
+      assert_predicate Rails.application.config, :seeding_wrapped_by_executor
     end
 
-    test "jobs are ran with original adapter while loading seeds with custom adapter configured" do
+    test "inline jobs do not clear CurrentAttributes when loading seed data" do
       app_file "db/seeds.rb", <<-RUBY
-        Rails.application.config.seed_queue_adapter = ActiveJob::Base.queue_adapter
+        class SeedsAttributes < ActiveSupport::CurrentAttributes
+          attribute :foo
+        end
+
+        class SeedsJob < ActiveJob::Base
+          self.queue_adapter = :inline
+          def perform
+            Rails.application.config.seeds_job_ran = true
+          end
+        end
+
+        SeedsAttributes.foo = 42
+        SeedsJob.perform_later
+        Rails.application.config.seeds_attributes_foo = SeedsAttributes.foo
       RUBY
 
       boot_rails
-      Rails.application.config.active_job.queue_adapter = :delayed_job
       Rails.application.load_seed
 
-      assert_instance_of ActiveJob::QueueAdapters::DelayedJobAdapter, Rails.application.config.seed_queue_adapter
-      assert_instance_of ActiveJob::QueueAdapters::DelayedJobAdapter, ActiveJob::Base.queue_adapter
+      assert Rails.application.config.seeds_job_ran
+      assert_equal 42, Rails.application.config.seeds_attributes_foo
     end
 
     test "seed data can be loaded when ActiveJob is not present" do