Getting Started with Resilience4j: Circuit Breaker, Rate Limiter, Bulkhead, Retry, Cache, and TimeLimiter

Resilience4j is a modern, lightweight fault‑tolerance library inspired by Hystrix, offering modular components for circuit breaking, rate limiting, bulkhead isolation, retries, caching, and time limiting to build robust microservice systems.

Maven setup : Add the desired Resilience4j modules as dependencies in your pom.xml , for example the circuit‑breaker module, and include additional modules as needed.

Circuit Breaker : The circuit‑breaker monitors remote calls and opens when a failure threshold is reached, preventing cascading failures. You can use the default configuration or customize parameters such as failure rate threshold and wait duration, then create a CircuitBreaker instance and decorate remote calls.

Rate Limiter : By adding the resilience4j‑ratelimiter dependency, you can limit the rate of calls to a service. Configure the refresh period, limit per period, and timeout, then wrap functions with RateLimiter.decorateFunction .

Bulkhead : The resilience4j‑bulkhead module restricts the number of concurrent calls to a service. Define the maximum parallel calls and thread‑wait time, then use the Bulkhead API to protect critical sections.

Retry : Include resilience4j‑retry to automatically retry failed calls. Configure maximum attempts, wait interval, custom back‑off functions, and predicates to decide which exceptions should be retried.

Cache : The resilience4j‑cache module integrates with JSR‑107 caches. It provides cache decorators for Supplier and Callable types, allowing cached results for idempotent operations.

TimeLimiter : Adding resilience4j‑timelimiter lets you set a maximum execution time for remote calls. Configure a timeout (e.g., 1 ms) and combine the TimeLimiter with other modules such as the circuit‑breaker.

Additional modules : Resilience4j offers integrations with popular frameworks like Spring Boot, Ratpack, Retrofit, Vert.x, Dropwizard, and Prometheus, simplifying adoption in existing projects.

Conclusion : By using Resilience4j’s modular features, developers can address various fault‑tolerance concerns in microservice communication, improving system stability and resilience.