Stop keepAlive crawler after all requests are finished

[uiii]

Hello,
I have two crawlers, one running with keepAlive: true (call it A) and the second running normally (call it B), which adds request to the crawler A. After the cralwer B finishes I'd like to keep the crawler A running until it finishes all the requests and then stop the script. I tried the teardown method but it stops the crawler without finishing the queue.