resilience4j Spring Boot 2 - spring-boot

Question

Trying out a simple Spring Boot 2 + Resilience4j project.
But facing an issue that the circuit breaker is always CLOSED though the host application is down.
Service class
#Autowired
private RestTemplate restTemplate;
#Bean
public RestTemplate restTemplate() {
return new RestTemplate();
}
#CircuitBreaker(name = "mainService", fallbackMethod="testFallBack")
public ResponseEntity<String> invokeService(int i) {
return restTemplate.exchange(
"http://localhost:9092/", // This service is always down
HttpMethod.GET,
null,
String.class
);
}
private ResponseEntity<String> testFallBack(int i, Exception e) {
return new ResponseEntity<String>("In fallback method", HttpStatus.INTERNAL_SERVER_ERROR);
}
Resilience4J Config
management.endpoint.health.show-details: always
management.health.circuitbreakers.enabled: true
resilience4j:
circuitbreaker:
configs:
default:
registerHealthIndicator: true
minimumNumberOfCalls: 5
permittedNumberOfCallsInHalfOpenState: 3
automaticTransitionFromOpenToHalfOpenEnabled: true
waitDurationInOpenState: 5s
failureRateThreshold: 50
eventConsumerBufferSize: 10
instances:
mainService:
baseConfig: default
The Service is being called multiple times from the Controller and I expect it to fallback after minimum 5 calls but the circuit breaker is always CLOSED and for each call from controller the host service is being called and up with Connection refused.
Dependencies: spring-boot-starter-web, resilience4j-spring-boot2, spring-aop, spring-boot-starter-actuator
Earlier I tried out programmatic approach using CircuitBreakerRegistry and Decorator Function which works as expected.

Answer 1

Actually, you misunderstand the circuit breaker parameters. See the documentation:
minimumNumberOfCalls, default: 100
Configures the minimum number of calls which are required (per sliding window period) before the CircuitBreaker can calculate the error rate or slow call rate.
For example, if minimumNumberOfCalls is 10, then at least 10 calls must be recorded, before the failure rate can be calculated.
If only 9 calls have been recorded the CircuitBreaker will not transition to open even if all 9 calls have failed.
slidingWindowSize, default: 100
Configures the size of the sliding window which is used to record the outcome of calls when the CircuitBreaker is closed.
In your configuration, there is
minimumNumberOfCalls: 5
slidingWindowSize: 100 ## implicitly, because you have not set this parameters
And you
expect it to fallback after minimum 5 calls
However, your circuit breaker opens after 100 failures, not after 5.