Circuit Breaker Pattern in Go: How to Prevent Cascading Service Failures

The circuit breaker pattern in Go helps prevent cascading failures by stopping a service from repeatedly calling an unhealthy dependency. It operates across three states — closed (normal traffic), open (requests rejected immediately), and half-open (limited trial requests) — transitioning based on failure thresholds and cool-down periods. The pattern is particularly valuable for outbound calls to HTTP APIs, payment gateways, microservices, and other dependencies that may become slow or overloaded. Slow dependencies are often more dangerous than hard failures, as they can exhaust goroutines, memory, and connections, eventually degrading the calling service itself. Circuit breakers are distinct from timeouts and retries, each solving a different problem: timeouts bound a single call's duration, retries handle transient errors, while circuit breakers protect against sustained dependency unhealthiness.