Basic throttler

throttler.rb

class Throttler

  class << self

    def limit *attrs
      throttler.limit *attrs
    end

    private

      def throttler
        @throttler ||= new
      end

  end

  attr_reader :storage

  def initialize storage=nil
    @mutex    = Mutex.new
    @storage  = storage || Hash.new
  end

  def limit seconds, key='default'
    while not allowed?(seconds, key)
      sleep 0.01
    end

    yield if block_given?
  end

  private

    def allowed? seconds, key
      @mutex.synchronize do
        now       = Time.now.to_f
        timestamp = get(key)

        if timestamp.nil? or timestamp < now - seconds
          set(key, now)
          true
        else
          false
        end

      end
    end

    def get key
      value = storage[key]

      if value and not value.is_a?(Float)
        value.to_f
      else
        value
      end
    end

    def set key, value
      storage[key] = value
    end

end

Usage examples

Limit rate

Throttler.limit 1.minute do
  do_request_to_api
end

Limit rate with personal lock

threads = []

threads << Thread.new do
  Throttler.limit(10.seconds, "API_1") { do_request_to_api_1 }
end

threads << Thread.new do
  Throttler.limit(15.seconds, "API_2") { do_request_to_api_2 }
end

threads.each(&:join)

Use Redis as key-value storage

redis = Redis.new

throttler = Throttler.new redis

throttler.limit(1.minute) { do_request_to_api }