limits.md

!SLIDE

Don't block the reactor

EM.run do
  # many things...
  on_a_callback do
    compute_pi_decimals(1_000_000)
  end
end

!SLIDE

In fact, only one CPU is used

One thread, one process...

We are using only one core of our computer!

!SLIDE

Solutions

1. Split your task in many small parts and run the event loop between the parts
2. Delegate the computation to another thread or process

!SLIDE

Split

var n = 0;
var compute = function() {
  var pi = compute_nth_decimal(n);
  if (++n == 1000000) {
    console.log(pi);
  } else {
    process.nextTick(compute);
  }
}

!SLIDE

Split

decimals = (1..1_000_000).to_a
EM.tick_loop do
  if decimals.empty?
    :stop
  else
    compute_nth_decimal decimals.shift 
  end
end

!SLIDE

Delegate

operation = proc {
    compute_pi_decimals(1_000_000)
}
callback = proc {|result|
  puts result
}
EventMachine.defer(operation, callback)