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Spring / Resilience4j Interview questions

What is the difference between CallNotPermittedException and other Resilience4j exceptions?
ExceptionThrown by / meaning
CallNotPermittedExceptionCircuitBreaker is OPEN; the call was never attempted.
BulkheadFullExceptionBulkhead concurrency/queue limit reached; call rejected before running.
RequestNotPermittedRateLimiter's permit timeout expired; call was never attempted.
TimeoutExceptionTimeLimiter's duration elapsed while the call was actually running.

The common thread across the first three is that they all represent the call being refused before it ever reached the real dependency - the failure is entirely local, inside Resilience4j's own gatekeeping logic.

TimeoutException is different in kind: the call did start running against the actual dependency, it just didn't finish in time, which matters when deciding whether it's safe to assume the downstream side-effect happened or not.

CallNotPermittedException, BulkheadFullException, and RequestNotPermitted have in common that:
TimeoutException from TimeLimiter differs because:

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