resilience4j

Resilience4j is a fault tolerance library for Java™

Resilience4j is a lightweight fault tolerance library inspired by Netflix Hystrix, but designed for functional programming. Lightweight, because the library only uses Vavr, which does not have any other external library dependencies. Netflix Hystrix, in contrast, has a compile dependency to Archaius which has many more external library dependencies such as Guava and Apache Commons Configuration.

Resilience4j provides higher-order functions (decorators) to enhance any functional interface, lambda expression or method reference with a Circuit Breaker, Rate Limiter, Retry or Bulkhead. You can stack more than one decorator on any functional interface, lambda expression or method reference. The advantage is that you have the choice to select the decorators you need and nothing else.

Supplier<String> supplier = () -> backendService.doSomething(param1, param2);

Supplier<String> decoratedSupplier = Decorators.ofSupplier(supplier)
  .withRetry(Retry.ofDefaults("name"))
  .withCircuitBreaker(CircuitBreaker.ofDefaults("name"))
  .withBulkhead(Bulkhead.ofDefaults("name"));  

String result = Try.ofSupplier(decoratedSupplier)
  .recover(throwable -> "Hello from Recovery").get();

With Resilience4j you don’t have to go all-in, you can pick what you need.

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Examples

Examples of resilience4j-reactor

Decorate Mono or Flux with a CircuitBreaker

The following example shows how to decorate a Mono by using the custom Reactor operator. Flux is also supported.

The CircuitBreakerOperator checks if a downstream subscriber/observer can acquire a permission to subscribe to an upstream Publisher. If the CircuitBreaker is OPEN, the CircuitBreakerOperator emits a CallNotPermittedException to the downstream subscriber.

CircuitBreaker circuitBreaker = CircuitBreaker.ofDefaults("name");
Mono.fromCallable(backendService::doSomething)
    .compose(CircuitBreakerOperator.of(circuitBreaker))

Decorate Mono or Flux with a RateLimiter

The following example shows how to decorate a Mono by using the custom Reactor operator. Flux is also supported.

The RateLimiterOperator checks if a downstream subscriber/observer can acquire a permission to subscribe to an upstream Publisher. If the rate limit would be exceeded, the RateLimiterOperator could either delay requesting data from the upstream or it can emit a RequestNotPermitted error to the downstream subscriber.

RateLimiter rateLimiter = RateLimiter.ofDefaults("name");
Mono.fromCallable(backendService::doSomething)
    .compose(RateLimiterOperator.of(rateLimiter))

Decorate Mono or Flux with a Bulkhead

The following example shows how to decorate a Mono by using the custom Reactor operator. Flux is also supported.

The BulkheadOperator checks if a downstream subscriber/observer can acquire a permission to subscribe to an upstream Publisher. If the Bulhead is full, the BulkheadOperator emits a BulkheadFullException to the downstream subscriber.

Bulkhead bulkhead = Bulkhead.ofDefaults("name");
Mono.fromCallable(backendService::doSomething)
  .compose(BulkheadOperator.of(bulkhead));

Decorate Mono or Flux with Retry

Retry retry = Retry.ofDefaults("backendName");
Mono.fromCallable(backendService::doSomething)
    .compose(RetryOperator.of(retry))

Examples


Examples of resilience4j-reactor

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