Can I implement an own decorator for resilience4j to optimize rate limiting?

Question

I want to optimize the resilience4j rate limiter to allow

• a rate limiting per user
• a staggered rate limiting (like 1 call/second but only 30 calls/minute but only 1000 calls/hour).

This should protect a resource from DOS attacks but not limit the "normal" user.

Is it possible to reach this with the default resilience4j decorators or can I write my own decorator?

(Or is my approach completely wrong to counteract a DOS attack in this way?)

Answer 1

You might use .andThen(secondDecorator) like a fixed issue does mention

protected <T> Function<Publisher<T>, Publisher<T>> decorateWithCircuitBreakerForSpecificEndpoint() {
    final CircuitBreakerConfig circuitBreakerConfig = CircuitBreakerConfig.custom()
        .failureRateThreshold(100)
        .recordFailure(throwable -> throwable instanceof RuntimeException)
        .ringBufferSizeInClosedState(10)
        .ringBufferSizeInHalfOpenState(10)
        .waitDurationInOpenState(Duration.ofSeconds(5_000))
        .build();
    final CircuitBreaker circuitBreaker = this.circuitBreakerRegistry.circuitBreaker("test1", circuitBreakerConfig);
    return CircuitBreakerOperator.<T>of(circuitBreaker).andThen(decorateWithCircuitBreakerForSpecificHost());
}

protected <T> Function<Publisher<T>, Publisher<T>> decorateWithCircuitBreakerForSpecificHost() {
    final CircuitBreakerConfig circuitBreakerConfig = CircuitBreakerConfig.custom()
        .failureRateThreshold(10)
        .recordFailure(throwable -> throwable instanceof RuntimeException)
        .ringBufferSizeInClosedState(5)
        .ringBufferSizeInHalfOpenState(5)
        .waitDurationInOpenState(Duration.ofSeconds(5_000))
        .build();
    final CircuitBreaker circuitBreaker = this.circuitBreakerRegistry.circuitBreaker("test2", circuitBreakerConfig);
    return CircuitBreakerOperator.<T>of(circuitBreaker);
}