Testing a Circuit Breaker
Take a look at the circuit breaker calls and how to test our circuit breaker system.
We'll cover the following...
Understanding the system
Circuit breakers are one of the most interesting concepts in fault isolation for reliable systems. They are used to account for errors that happen over time in a part of the system. If the frequency at which the errors happen is considered too high compared to the successful cases, the breaker is tripped.
Once tripped, further calls automatically fail before having a chance to reach the subsystem gated by the breaker. The idea is that failures tend to be costly and take a lot of time, and a failing system under heavy stress is even harder to get back into a usable state. The circuit breaker helps us prevent the client from doing work that would result in expensive failures. Instead, we get cheap failures that the failing subsystem recuperate under less stress.
For this example, we’ll send tests to the circuit_breaker library from Klarna. But first, let’s see how it works.
Understanding circuit_breaker
Let’s start by taking a look at how the library works. After that, we can move on to writing tests for it.
The library can be used as a wrapper over a given function call. This wrapper looks at the return values and duration of each function ...