gistfile1.rb

require 'active_support/notifications'

ActiveSupport::Notifications.subscribe 'test_class.create' do |*args|
  event = ActiveSupport::Notifications::Event.new(*args)
  p event.payload
end

class TestClass
  def initialize
    @rand_int = rand(10)
  end

  def instr
    ActiveSupport::Notifications.instrument('test_class.create', rand_int: @rand_int)
  end
end

threads = []
400_000.times do
  threads << Thread.new { TestClass.new.instr }
end

threads.map(&:join)


#ConcurrencyError: Detected invalid array contents due to unsynchronized modifications with concurrent users
#         pop at org/jruby/RubyArray.java:1190
#      finish at /Users/kes/.rbenv/versions/jruby-1.7.4/lib/ruby/gems/shared/gems/activesupport-4.0.1.rc3/lib/active_support/notifications/fanout.rb:124
#      finish at /Users/kes/.rbenv/versions/jruby-1.7.4/lib/ruby/gems/shared/gems/activesupport-4.0.1.rc3/lib/active_support/notifications/fanout.rb:40
#        each at org/jruby/RubyArray.java:1617
#      finish at /Users/kes/.rbenv/versions/jruby-1.7.4/lib/ruby/gems/shared/gems/activesupport-4.0.1.rc3/lib/active_support/notifications/fanout.rb:40
#      finish at /Users/kes/.rbenv/versions/jruby-1.7.4/lib/ruby/gems/shared/gems/activesupport-4.0.1.rc3/lib/active_support/notifications/instrumenter.rb:36
#  instrument at /Users/kes/.rbenv/versions/jruby-1.7.4/lib/ruby/gems/shared/gems/activesupport-4.0.1.rc3/lib/active_support/notifications/instrumenter.rb:25
#  instrument at /Users/kes/.rbenv/versions/jruby-1.7.4/lib/ruby/gems/shared/gems/activesupport-4.0.1.rc3/lib/active_support/notifications/instrumenter.rb:19
#  instrument at /Users/kes/.rbenv/versions/jruby-1.7.4/lib/ruby/gems/shared/gems/activesupport-4.0.1.rc3/lib/active_support/notifications.rb:159
#       instr at notifications_thread_safety.rb:15
#      (root) at notifications_thread_safety.rb:21