throttle.rb

require 'redis'

$redis = Redis.new

GLOBAL = "counter_global"

def local
  "counter_sec_#{Time.now.to_i}"
end

Cap = 100

$redis.set(GLOBAL, 0)

def try_fetch(url)
  if $redis.get(GLOBAL).to_i <= Cap && $redis.incr(local).to_i <= Cap
    perform(url)
  else
    sleep(1)
    try_fetch(url)
  end
end

def perform(url)
  Thread.new do
    $redis.incr(GLOBAL)
    print "."
    $redis.decr(GLOBAL)
  end
end

1.upto(1000) do |i|
  try_fetch(i)
end

puts $redis.get(GLOBAL)