Fix memory leak - for idling workers

[kevinhq]

The fix is based on our company's need but we think it may be useful for others in community too.

[ghiculescu]

Here is how we are approaching it:

# frozen_string_literal: true

# Reloads autoloadable code as needed around each job execution
# See  https://github.com/mperham/sidekiq/pull/2457 /
# https://github.com/mperham/sidekiq/blob/461ef8392fe8503cda849769fc590a113bd04559/lib/sidekiq/rails.rb#L6 for inspiration

module Delayed
  module Plugins
    class Reloader < Plugin
      callbacks do |lifecycle|
        lifecycle.around(:invoke_job) do |_job, *_args, &block|
          ::Rails.application.reloader.wrap do
            block.call
          end
        end
      end
    end
  end
end

Delayed::Worker.plugins << Delayed::Plugins::Reloader

module DJUseOurOwnReloader
  module ClassMethods
    def reload_app?
      false
    end
  end

  def self.prepended(mod)
    mod.singleton_class.prepend(ClassMethods)
  end
end

Delayed::Worker.prepend(DJUseOurOwnReloader)

An equivalent change to DJ would:

• Remove the current reload? call.
• Add the plugin instead.

[girishgl]

Could you please provide more context or information regarding the specific situation or scenario in which you have observed the memory leak in the Delayed Job gem? This will help me using same code change in my organisation.

Moreover I have seen this exception often times. DO you have any idea about this?
SIGTERM /gems/gems/delayed_job-4.1.3/lib/delayed/worker.rb:160: