Introduce a circuit breaker

[mcweba]

If backends are gone all of the requests (from the queues as well as synchronous ones from the clients) might hang and run into a timeout. This can use up sockets pretty fast.

By introducing some kind of circuit breaker, the opening of connections to backends which timeout too often could be stopped and immediately return an error to the client for some time. This could prevent instances from "going down" by using up all its available sockets.

Check /~https://github.com/Netflix/Hystrix/wiki/Dashboard (Hystrix: Circuit Breaker from Netflix)