Error when using in Ractor

[ukolovda]

Ruby 3 introduced Ractor, allowing utilize more than 1 core of CPU.

But when I try use it (make second instance of Rails Application), I got the error:

ruby-3.2.3/gems/zeitwerk-2.6.13/lib/zeitwerk/registry.rb:122:in loader_for': can not get unshareable values from instance variables of classes/modules from non-main Ractors (Ractor::IsolationError)`

Full test code:

# frozen_string_literal: true

require "bundler/inline"

gemfile(true) do
  source "https://rubygems.org"

  gem "rails"
  # If you want to test against edge Rails replace the previous line with this:
  # gem "rails", github: "rails/rails", branch: "main"
end

require "active_support"
require "active_support/core_ext/object/blank"
require "minitest/autorun"

class TestApplication < Rails::Application
end

# Workaround of Railties error
Ractor.make_shareable(Rails::Railtie::ABSTRACT_RAILTIES)

main_app = Rails.application

class BugTest < Minitest::Test
  def test_stuff

    r = Ractor.new do
        app2 = TestApplication.new
    end

  end
end

Ruby 3.2.3

I don't sure that my approach is correct, but we can create multiple instance of application, it can reduce RAM usage for many applications in the world.

[fxn]

Ractors cannot even do concurrent require. For example, this:

# c.rb
class C
end

# foo.rb
r1 = Ractor.new do
  require './c.rb'
end

r2 = Ractor.new do
  require './c.rb'
end

r1.take
r2.take

raises

foo.rb:1: warning: Ractor is experimental, and the behavior may change in future versions of Ruby! Also there are many implementation issues.
#<Thread:0x0000000104ab9028 run> terminated with exception (report_on_exception is true):
<internal:/Users/fxn/.rbenv/versions/3.3.0/lib/ruby/site_ruby/3.3.0/rubygems/core_ext/kernel_require.rb>:39:in `require'#<Thread:0x0000000104b1d6e0 run> terminated with exception (report_on_exception is true):
<internal:/Users/fxn/.rbenv/versions/3.3.0/lib/ruby/site_ruby/3.3.0/rubygems/core_ext/kernel_require.rb>:39:in `require': can not access non-shareable objects in constant Kernel::RUBYGEMS_ACTIVATION_MONITOR by non-main ractor. (Ractor::IsolationError)

which was reported in https://bugs.ruby-lang.org/issues/19154.

As the error says, this is an experimental feature. By now, I am closing.

[casperisfine]

To add to this, if you want to use Ractors, you should eager load your application, that's easy to do with Zeitwerk.

[ukolovda]

@fxn , @casperisfine thank you! I will try it.