Rails + Threads + constantize

_instructions.md

1. Create a vanilla Rails

   rails _5.0.7_ new vanilla_test --skip-yarn --skip-active-storage --skip-action --skip-sprockets --skip-spring --skip-listen --skip-coffee --skip-javascript --skip-turbolinks --skip-test --skip-system-test --skip-bootsnap
   

2. Copy the files into the right spots

3. Run it

   bin/rails r lock_it_up.rb
   

Interesting points:

• bundle exec rails r doesn't seem to work
• can't reproduce the lockup even with the slowdown thing
• Might be related to rails/rails#24028

foo_concern.rb

# app/models/concerns/foo_concern.rb
module FooConcern
  def blah
  end
end

foo_model.rb

# app/models/foo_model.rb
class FooModel < ApplicationRecord
  # # Some slow operation to allow another thread to get in here.
  # puts "#{Thread.current} Start slowdown"
  # t1 = Time.now
  # until Time.now >= t1 + 3
  # end
  # puts "#{Thread.current} End slowdown"

  include FooConcern
end

lock_it_up.rb

puts "Start."

t1 = Thread.new do
  #ActiveSupport::Dependencies.interlock.permit_concurrent_loads do
    "FooModel".constantize
  #end
end

t2 = Thread.new do
  #ActiveSupport::Dependencies.interlock.permit_concurrent_loads do
    "FooModel".constantize
  #end
end

t1.join
t2.join

puts "Done."