Registering failed attempt inside checked function seems to be counted double - circuit-breaker

Question

I'm exploring resilience4j and would like to both be able to record a failure for a circuit breaker inside a checked function, as well as returning a meaningful result. But the failure seems to be counted double when I do.
I'm using version 0.13.1:
<dependency>
<groupId>io.github.resilience4j</groupId>
<artifactId>resilience4j-circuitbreaker</artifactId>
<version>0.13.1</version>
</dependency>
Check the following test, we have a closed ring buffer of 10 which indicates that 10 calls should be evaluated before the CircuitBreaker can be tripped open. This is the case except when recording a failure with the circuitbreaker's onError method inside a checked function:
#Test
public void testRecordFailure() {
CircuitBreakerConfig config = CircuitBreakerConfig.custom()
.ringBufferSizeInClosedState(10)
.build();
CircuitBreakerRegistry registry = CircuitBreakerRegistry.of(config);
CircuitBreaker breaker1 = registry.circuitBreaker("breaker-1");
CircuitBreaker breaker2 = registry.circuitBreaker("breaker-2");
CheckedFunction0<String> supplier2 = CircuitBreaker.decorateCheckedSupplier(breaker2, () -> {
throw new RuntimeException();
});
CircuitBreaker breaker3 = registry.circuitBreaker("breaker-3");
CheckedFunction0<String> supplier3 = CircuitBreaker.decorateCheckedSupplier(breaker3, () -> {
breaker3.onError(0, new RuntimeException());
return "meaningful-result";
});
for (int i = 0; i < 4; i++) {
breaker1.onError(0, new RuntimeException());
Try.of(supplier2);
Try.of(supplier3);
}
assertEquals(CircuitBreaker.State.CLOSED, breaker1.getState()); // Success
assertEquals(CircuitBreaker.State.CLOSED, breaker2.getState()); // Success
assertEquals(CircuitBreaker.State.CLOSED, breaker3.getState()); // Success
breaker1.onError(0, new RuntimeException());
Try.of(supplier2);
Try.of(supplier3);
assertEquals(CircuitBreaker.State.CLOSED, breaker1.getState()); // Success
assertEquals(CircuitBreaker.State.CLOSED, breaker2.getState()); // Success
assertEquals(CircuitBreaker.State.CLOSED, breaker3.getState()); // Failure - circuit is now OPEN - why?
}
I've not been able to find an explanation for this behaviour, or if there it exists a way to record a failure for a circuit breaker inside a checked function. Can anybody shed some light on this?
Cheers!

Answer 1

You don't have to invoke onError. It's done by the higher order function.