Load Average

This implements UNIX-style load average computation.

For a more in depth discussion, see this article.

Yes, there are global variables. This was designed as a system-wide calculator
but could easily be modified to track multiple types of events.

@nakajima points out that it's constant time. And that's a good thing.

Usage

There are two major operations: tick and compute.

When whatever you want to measure (e.g. requests, jobs, etc) happens, call
tick.

On some interval, you need to call compute. You must pass that interval to
compute.

Dramatization (code did not actually happen)

require 'rubygems'
require 'eventmachine'
require 'load_average'

INTERVAL = 5 #seconds

EventMachine.run do
  EventMachine::add_periodic_timer(INTERVAL) do
    LoadAverage.compute(INTERVAL)
    puts $load.inspect
  end

  # Simulate events
  EventMachine::add_periodic_timer(0.25) do
    (10000.0 * rand).to_i.times do
      LoadAverage.tick
    end
  end
end

Credits

Some UNIX guys?