Circuit Breaker Pattern

Retries help with short failures, but they cannot fix a dependency that is down for longer.

A circuit breaker stops calling a failing dependency for a while. Instead of wasting resources on calls that are likely to fail, it fails fast, protects the caller, and gives the dependency time to recover.

This chapter covers closed, open, and half-open states, how breakers trip, how they test recovery, what to return while open, and how circuit breakers interact with retries.