Unblocking EventMachine's deferred callbacks

em-dc-unblock.rb

#!/usr/bin/ruby 

# Example of how to unblock EventMachine's deffered callbacks
# Based on http://stackoverflow.com/a/11778588/632827
# For output example see: http://goo.gl/d6E9E0

require 'eventmachine'

iam = [ 'blocking', 'non-blocking' ]

def unBlock &blocking
  proc { EM.defer(blocking) }
end

work = proc {
  puts "[#{Time.now}] I'm a blocking worker, I'll be done in 2 secs"
  sleep 2
  puts "[#{Time.now}] worker done!"
}

callback = proc {
  puts "[#{Time.now}] I'm a %s callback, I'll be done in 4 secs" % iam.shift
  sleep 4
  puts "[#{Time.now}] callback done!"
}

EM.run do
  EM.add_periodic_timer(1) { puts "[#{Time.now}] ." }

  EM.defer(work, callback )
  # Lets do the same thing in a bit but unblocked
  EM.add_timer(7) {
    EM.defer(work, unBlock {callback.call} )
  }

  EM.add_timer(15) { puts "[#{Time.now}] Bye!"; EM.stop }
end

A good example is processing an http callback unBlock'ed:

slow = URI("http://httpbin.org/delay/5")
http = EventMachine::HttpRequest.new(slow).get
procEssHTTP = proc { puts "1";sleep 2; puts "3" }
http.callback &unBlock {procEssHTTP.call}