Mastering Python Design Patterns - Second Edition

The Circuit Breaker pattern

One approach to fault tolerance involves timeouts and retries, as we have just seen. But, when a failure due to the communication with an external component is likely to be long-lasting, using a retry mechanism can affect the responsiveness of the application. We might be wasting time and resources trying to repeat a request that's likely to fail. This is where another pattern can be useful, the Circuit Breaker.

With circuit breaker, you wrap a fragile function call (or an integration point with an external service) in a special (circuit breaker) object, which monitors for failures. Once the failures reach a certain threshold, the circuit breaker trips, and all further calls to the circuit breaker return with an ...