Custom ShopifyAPI connection class with 429-retrial and throttling

api_connection.rb

class ApiConnection < ShopifyAPI::Connection
  cattr_accessor :logger
  self.logger = Logger.new(STDOUT) # for now

  class_attribute :leak_rate
  self.leak_rate = 2 # 2 per second

  class_attribute :call_limit_header
  self.call_limit_header = 'X-Shopify-Shop-Api-Call-Limit'

  class_attribute :min_call_buffer
  self.min_call_buffer = 2

  def handle_response(response)
    super.tap do
      num_calls, limit = response.header[call_limit_header].split('/').map(&:to_i)
      if limit - num_calls < min_call_buffer
        self.wait_until = Time.now + ((num_calls + min_call_buffer - limit).to_f/leak_rate).seconds
      end
      logger.debug("API Calls used: #{num_calls}/#{limit}")
    end
  end

  def request(*)
    if wait_until
      sleep_time = wait_until - Time.now
      if sleep_time > 0
        logger.debug "waiting #{sleep_time} seconds to allow bucket to drain"
        sleep(sleep_time)
      end
    end

    with_retrial do
      super
    end
  end

  private

  attr_accessor :wait_until

  def with_retrial
    num_retries = 5
    min_wait = 2
    retries_left = num_retries

    loop do
      begin
        return yield
      rescue ActiveResource::ClientError => e
        if e.response.code.to_i == 429 && retries_left > 0
          retries_left -= 1

          wait_time = e.response['Retry-After'.freeze].to_i
          wait_time = min_wait if wait_time < min_wait
          logger.info "Got a 429, will retry in #{wait_time} seconds"
          sleep(wait_time)

          next
        else
          raise
        end
      end
    end

  end
end