minimumNumberOfCalls not working in resilience4j - spring-boot

Question

Using springboot 2.4 and resilience4j 1.5,
i have configured my yaml file,
resilience4j:
circuitbreaker:
configs:
default:
registerHealthIndicator: true
slidingWindowSize: 10
minimumNumberOfCalls: 5
permittedNumberOfCallsInHalfOpenState: 3
automaticTransitionFromOpenToHalfOpenEnabled: true
waitDurationInOpenState: 50s
failureRateThreshold: 50
eventConsumerBufferSize: 10
instances:
movieCatalog:
baseConfig: default
and in the movieCatalog instance,
#RequestMapping("/{userId}")
#CircuitBreaker(name = CATALOG_SERVICE, fallbackMethod="fallBackCatalog")
public List<CatalogItem> getCatalog(#PathVariable("userId") String userId) {
UserRating ratings = restTemplate.getForObject("http://ratings-data-service/ratingsdata/users/"+userId, UserRating.class);
return ratings.getUserRatings().stream()
.map(rating -> {
Movie movie = restTemplate.getForObject("http://movie-info-sevice/movies/" + rating.getMovieId(), Movie.class);
return new CatalogItem(movie.getName(), movie.getDescription(), rating.getRating());
})
.collect(Collectors.toList());
}
private List<CatalogItem> fallBackCatalog(Exception e) {
List<CatalogItem> fallBack = new ArrayList<>();
fallBack.add(new CatalogItem("movie1", "movie desc", 3));
return fallBack;
}
i see that when i get an exception in the above getCatalog method the i get the fallback result immediately on the first call. my understanding is for the first 5 calls i should see an exception and from the 6 th call since more than 50% of the calls are exceptions(100% errors) i should see the fallback result in the 6th call. i have several errors before configuring fall back method, is there a cache which records the previous calls, and i guess if at all there is cache it should be cleared when the spring boot app is restarted right ? please explain if im missing something. any pointers are greatly appreciated.

Answer 1

The fallback mechanism is like a try/catch. It's independent of your CircuitBreaker configuration.
If you only want to execute a fallback method when the CircuitBreaker is open, then narrow down the scope from Exception to CallNotPermittedException.

Answer 2

Resilience4J will fail-fast by throwing a CallNotPermittedException until the state changes to closed or according to our configuration.
So with a fallback method, when the circuit breaker trips to Open state, it will no longer throw a CallNotPermittedException but instead will return the response INTERNAL_SERVER_ERROR.
I also agree with #Robert Winkler