I have a scenario I want to log each retry attempt and when the last one fails (i.e. maxAttempts
reached) a exception is thrown and let's say an entry to a database is created.
I try to achieve this using Resilience4j-retry with Spring Boot, therefore I use application.yml
and annotations.
@Retry(name = "default", fallbackMethod="fallback")
@CircuitBreaker(name = "default", fallbackMethod="fallback")
public ResponseEntity<List<Person>> person() {
return restTemplate.exchange(...); // let's say this always throws 500
}
The fallback logs the cause of the exception into an application log.
public ResponseEntity<?> fallback(Exception e) {
var status = HttpStatus.INTERNAL_SERVER_ERROR;
var cause = "Something unknown";
if (e instanceof ResourceAccessException) {
var resourceAccessException = (ResourceAccessException) e;
if (e.getCause() instanceof ConnectTimeoutException) {
cause = "Connection timeout";
}
if (e.getCause() instanceof SocketTimeoutException) {
cause = "Read timeout";
}
} else if (e instanceof HttpServerErrorException) {
var httpServerErrorException = (HttpServerErrorException) e;
cause = "Server error";
} else if (e instanceof HttpClientErrorException) {
var httpClientErrorException = (HttpClientErrorException) e;
cause = "Client error";
} else if (e instanceof CallNotPermittedException) {
var callNotPermittedException = (CallNotPermittedException) e;
cause = "Open circuit breaker";
}
var message = String.format("%s caused fallback, caught exception %s",
cause, e.getMessage());
log.error(message); // application log entry
throw new MyRestException (message, e);
}
When I call this method person()
the retry happens as maxAttempt
configured. I expect my custom runtime MyRestException
is caught on each retry and thrown on the last one (when maxAttempt
is reached), so I wrap the call in the try-catch.
public List<Person> person() {
try {
return myRestService.person().getBody();
} catch (MyRestException ex) {
log.error("Here I am ready to log the issue into the database");
throw new ex;
}
}
Unfortunatelly, the retry seems to be ignored as the fallback encounters and rethrows the exception that is immediatelly caught with my try-catch
instead of the Resilience4j-retry mechanism.
How to achieve the behavior when the maxAttempts
is hit? Is there a way to define a specific fallback method for such case?
Why don't you catch and map exceptions to MyRestException
inside of your Service methods, e.g. myRestService.person()
?
It makes your configuration even simpler, because you only have to add MyRestException
to the configuration of your RetryConfig and CircuitBreakerConfig.
Spring RestTemplate also has mechanisms to register a custom ResponseErrorHandler, if you don't want to add the boilerplate code to every Service method. -> https://www.baeldung.com/spring-rest-template-error-handling
I would not map CallNotPermittedException
to MyRestException
. You don't want to retry when the CircuitBreaker is open. Add CallNotPermittedException
to the list of ignored exceptions in your RetryConfig.
I think you don't need the fallback mechanism at all. I thing mapping an exception to another exception is not a "fallback".