Resilience4j Retry – logging retry attempts from client?

Is it possible to log retries attempts on client side with resilience4j please?

Maybe via some kind of configuration, or settings.

Currently, I am using resilience4j with Spring boot Webflux annotation based.

It is working great, the project is amazing.

While we put server logs on server side, to see that a same http call has been made due to a retry (we log time, client IP, request ID, etc…) Would I be possible to have client side logs?

I was expecting to see something like “Resilience4j – client side: 1st attempt failed because of someException, retying with attend number 2. 2nd attempt failed because of someException, retying with attend number 3. 3rd attempt successful!”

Something like that. Is there a property, some config, some setup, that can help to do this easily please? Without adding too much boiler code.

@RestController
public class TestController {

    private final WebClient webClient;

    public TestController(WebClient.Builder webClientBuilder) {
        this.webClient = webClientBuilder.baseUrl("http://localhost:8443/serviceBgreeting").build();
    }

    @GetMapping("/greeting")
    public Mono<String> greeting() {
        System.out.println("Greeting method is invoked ");
        return someRestCall();
    }

    @Retry(name = "greetingRetry")
    public Mono<String> someRestCall() {
        return this.webClient.get().retrieve().bodyToMono(String.class);
    }

}

Thank you

Answer

Fortunately (or unfortunately) there is an undocumented feature 🙂

You can add a RegistryEventConsumer Bean in order to add event consumers to any Retry instance.

    @Bean
    public RegistryEventConsumer<Retry> myRetryRegistryEventConsumer() {

        return new RegistryEventConsumer<Retry>() {
            @Override
            public void onEntryAddedEvent(EntryAddedEvent<Retry> entryAddedEvent) {
                entryAddedEvent.getAddedEntry().getEventPublisher()
                   .onEvent(event -> LOG.info(event.toString()));
            }

            @Override
            public void onEntryRemovedEvent(EntryRemovedEvent<Retry> entryRemoveEvent) {

            }

            @Override
            public void onEntryReplacedEvent(EntryReplacedEvent<Retry> entryReplacedEvent) {

            }
        };
    }

Log entry look as follows:

2020-10-26T13:00:19.807034700+01:00[Europe/Berlin]: Retry 'backendA', waiting PT0.1S until attempt '1'. Last attempt failed with exception 'org.springframework.web.client.HttpServerErrorException: 500 This is a remote exception'.

2020-10-26T13:00:19.912028800+01:00[Europe/Berlin]: Retry 'backendA', waiting PT0.1S until attempt '2'. Last attempt failed with exception 'org.springframework.web.client.HttpServerErrorException: 500 This is a remote exception'.

2020-10-26T13:00:20.023250+01:00[Europe/Berlin]: Retry 'backendA' recorded a failed retry attempt. Number of retry attempts: '3'. Giving up. Last exception was: 'org.springframework.web.client.HttpServerErrorException: 500 This is a remote exception'.