singletons.rb

#!/usr/bin/env ruby
# frozen_string_literal: true

example_description = <<DESC

  Sub Plans Example
  ===================

  This example shows, how singleton actions can be used for making sure
  there is only one instance of the action running at a time.

  Singleton actions try to obtain a lock at the beggining of their plan
  phase and fail if they can't do so. In run phase they check if they
  have the lock and try to acquire it again if they don't. These actions
  release the lock at the end of their finalize phase.

DESC

require_relative 'example_helper'

class SingletonExample < Dynflow::Action
  include Dynflow::Action::Singleton

  def run
    sleep 10
  end
end

class SingletonExampleA < SingletonExample; end
class SingletonExampleB < SingletonExample; end

if $0 == __FILE__
  ExampleHelper.world.action_logger.level = Logger::INFO
  ExampleHelper.world
  t1 = ExampleHelper.world.trigger(SingletonExampleA)
  t2 = ExampleHelper.world.trigger(SingletonExampleA)
  ExampleHelper.world.trigger(SingletonExampleA) unless SingletonExampleA.singleton_locked?(ExampleHelper.world)
  t3 = ExampleHelper.world.trigger(SingletonExampleB)
  db = ExampleHelper.world.persistence.adapter.db

  puts example_description
  puts <<-MSG.gsub(/^.*\|/, '')
    |  3 execution plans were triggered:
    |  #{t1.id} should finish successfully
    |  #{t3.id} should finish successfully because it is a singleton of different class
    |  #{t2.id} should fail because #{t1.id} holds the lock
    |
    |  You can see the details at
    |    #{ExampleHelper::DYNFLOW_URL}/#{t1.id}
    |    #{ExampleHelper::DYNFLOW_URL}/#{t2.id}
    |    #{ExampleHelper::DYNFLOW_URL}/#{t3.id}
    |
  MSG
  ExampleHelper.run_web_console
end