EventMachine - how can you tell if you're falling behind?

Question

I'm looking into using the EventMachine powered twitter-stream rubygem to track and capture tweets. I'm kind of new to the whole evented programming thing. How can I tell if whatever processing I'm doing in my event loop is causing me to fall behind? Is there an easy way to check?

Answer 1

You can determine the latency by using a periodic timer and printing out the elapsed time. If you're using a timer of 1 second you should have about 1 second elapsed, if it's greater you know how much you're slowing down the reactor.

@last = Time.now.to_f
EM.add_periodic_timer(1) do
  puts "LATENCY: #{Time.now.to_f - @last}"
  @last = Time.now.to_f
end 

Answer 2

EventMachine has a EventMachine::Queue.size method that lets you peek at the current queue and get an idea how big it is.

You could add_periodic_timer() and, in that event, get the size of the queue and print it.

If the number is not getting smaller you are at parity. If it's going up you are falling behind.