resilience4jspringboot2

Resilience4j is a lightweight fault tolerance library for the Java platform designed to help developers build resilient, responsive applications. Inspired by Hystrix, resilience4j offers a family of pluggable patterns that can be applied to individual calls or entire services, with low overhead and minimal runtime dependencies.

Its design is modular: core components provide circuit breakers, retries, time limiters, bulkheads, and rate limiters as separate modules (resilience4j-circuitbreaker, resilience4j-retry, resilience4j-timelimiter, resilience4j-bulkhead, resilience4j-ratelimiter). Each module can be used independently or composed together on a call to decorate a Supplier, Callable, or CompletionStage. The circuit breaker tracks failures and can open or half-open states; the retry pattern handles transient failures; the time limiter enforces operation deadlines; the bulkhead limits concurrent calls; the rate limiter enforces throughput constraints. The library also supports event listeners and health metrics.

Usage is designed to be straightforward for plain Java and popular frameworks. Calls are wrapped with a decorator and executed through the resilience patterns, and results or exceptions are propagated to the caller. It integrates with Spring Boot via dedicated starters and supports metrics reporting through Micrometer or other monitoring stacks.

Resilience4j is open source under the Apache 2.0 license. It is actively developed, community-driven, and widely adopted in microservice architectures as an alternative to heavier resilience tools, offering a lightweight, composable approach to fault tolerance.