spring-boot-resilience4j

Circuit breakers stop requests to failing services by monitoring call outcomes and opening when failures exceed a threshold. Use Resilience4j's @CircuitBreaker annotation on Spring Boot service methods to automatically manage state transitions between closed, open, and half-open states, protecting downstream dependencies from overload.

Resilience4j provides @Retry and @TimeLimiter annotations that automatically retry failed requests and enforce execution deadlines on Spring Boot methods. Configure retry policies and timeout thresholds in YAML to handle transient failures and prevent indefinite hangs when calling external services.

Bulkheads isolate thread pools to limit concurrent requests per operation, while rate limiters control request velocity. Resilience4j's @Bulkhead and @RateLimiter annotations on Spring Boot methods prevent one slow dependency from consuming all threads or overwhelming a service under load.

Yes. Resilience4j integrates seamlessly with Spring AOP to apply fault-tolerance patterns via annotations like @CircuitBreaker, @Retry, @RateLimiter, @Bulkhead, and @TimeLimiter on service methods. Configure patterns in YAML and Spring automatically applies aspect-driven resilience at runtime.

Fallbacks define alternative responses when protected methods fail. Combine Resilience4j patterns with Spring's @Fallback or method-level fallback handlers to return cached data, default values, or graceful degradation when circuit breakers open or retries exhaust.

Resilience4j exports metrics on circuit breaker state changes, retry attempts, rate limit rejections, bulkhead saturation, and timeout occurrences. Integrate with Spring Boot Actuator and monitoring platforms to observe resilience pattern behavior and alert on failures.