Property-Based Testing with PropEr, Erlang, and Elixir

Testing a Circuit Breaker

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 allows you to prevent the client from doing work that would result in expensive failures and directly turn them into a cheap failures, ...