throttle.rb

require 'singleton'

class AtMost
  include Singleton

  def initialize
    @table = Hash.new { |h, k| h[k] = -1 }
  end

  def call(n)
    key = caller(1, 2)
    yield if (@table[key] = (@table[key] + 1) % n).zero?
  end

  def self.call(n)
    instance.call(n) { yield }
  end
end

class Throttle
  include Singleton

  def initialize
    @table = Hash.new { |h, k| h[k] = Time.at(0) }
  end

  def call(delay)
    key = caller(1, 2)
    was = @table[key]
    now = Time.now
    if now - was >= delay
      @table[key] = now
      yield
    end
  end

  def self.call(n)
    instance.call(n) { yield }
  end
end

require 'logger'
logger = Logger.new($stdout)

logger.info "Testing AtMost"

1000.times do # should print "foo" 10 times and "bar" 10 times
  AtMost.call(100) { logger.info "foo" }
  AtMost.call(100) { logger.info "bar" }
end

logger.info "Testing Throttle"

30.times do # should print "foo" ~ 3 times
  Throttle.call(1) { logger.info "foo" }
  sleep(0.1)
end