Log response time when success & when error - Webflux (doOnSuccess gets called even with error)

Question

I have written this filter to measure the response time for APIs. onSuccess gets triggered when I get the error. Is there any way to log on success and on error respectively for better logging.

public class RequestTimingFilter implements WebFilter {

  @Override
  public Mono<Void> filter(ServerWebExchange exchange, WebFilterChain chain) {
    if (exchange.getRequest().getPath().value().contains("something")) {
      long startMillis = System.currentTimeMillis();
      return chain
          .filter(exchange)
          .doOnSuccess(
              success ->
                  log.info(
                      "Api call successfull: {}ms",
                      System.currentTimeMillis() - startMillis));
    }
    return chain.filter(exchange);
  }
}

Answer 1

I was able to achieve this by using the below code -

return chain
          .filter(exchange)
          .then(
              Mono.fromRunnable(
                  () -> {
                    ServerHttpResponse response = exchange.getResponse();
                    if (Objects.requireNonNull(response.getStatusCode()).is2xxSuccessful()) {
                      log.info(
                          "Success: {}ms",
                          System.currentTimeMillis() - startMillis);
                    } else {
                      log.info("Failure");
                    }
                  }));