sync_vs_async.rb

require 'thread'
Thread.abort_on_exception = true
require 'rubygems'
require 'eventmachine'

class AsyncTime
  def self.now
    EM.add_timer(2){ yield(Time.now) }
  end
end

class SyncTime
  def self.now
    raise 'must run in separate thread' if Thread.current == Thread.main
    q = Queue.new
    AsyncTime.now{|t| q.push(t) }
    q.pop
  end
end

EM.run{

  EM.add_timer(1){ p [:timer, Time.now] }

  Thread.new{ p [:sync, SyncTime.now] }
  AsyncTime.now{ |t| p [:async, t] }
  
  EM.add_timer(2){ EM.stop }
  
}

__END__

[:timer, Thu Aug 07 23:09:37 -0700 2008]
[:sync, Thu Aug 07 23:09:38 -0700 2008][:async, Thu Aug 07 23:09:38 -0700 2008]