A Circuit Breaker is a design pattern used in microservices to handle failures and prevent cascading errors. It acts as a safety mechanism that detects failures in a service and prevents further calls to that service, allowing the system to recover gracefully.

  • How it works:
    • When a service repeatedly fails or becomes unresponsive, the circuit breaker “opens” to stop further requests from being sent to the failing service.
    • The circuit breaker can “close” again after a predefined time, and a new attempt is made to call the service. If it succeeds, the circuit breaker “closes,” allowing normal communication to resume.
    • It can also “half-open” to test whether the service has recovered without impacting the entire system.
  • Key states of a Circuit Breaker:
    • Closed: The service is functioning properly, and requests are being sent.
    • Open: The service is down or failing repeatedly, so requests are blocked to prevent further damage.
    • Half-Open: A temporary state where the system attempts to send a limited number of requests to see if the service has recovered.
  • Benefits:
    • Fault Isolation: Prevents failure from propagating across the system, keeping unaffected services functional.
    • Graceful Degradation: Allows the system to continue functioning even when some services are down.
    • Improved Stability: By avoiding continuous retries to a failing service, the circuit breaker helps prevent system overloads.

In Spring Boot, the Resilience4J or Hystrix libraries are commonly used to implement the Circuit Breaker pattern.

In summary, the Circuit Breaker pattern in microservices enhances system resilience by preventing cascading failures, improving stability, and allowing services to recover more gracefully.