▪ Fallback Pattern provides an alternative behavior or response

if a request fails or times out.

▪ If a service is unavailable, the client could use a cached

version of the data or display a default message to the user.

▪ It is used to provide an alternative course of action when a

service call fails or takes too long to complete.

▪ Define a fallback function that is called if the service call fails

or times out, and the function provides an alternative

response.

▪ In microservices, the fallback pattern help to improve the

overall reliability and stability of the system.

▪ If the payment processing service is unavailable or takes too

long to complete a request, the fallback pattern could be used

to provide an alternative response.

▪ I.e. displaying an error message or offering the user the option

to try again later.

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@Service

public class BookService {

​

  private static final Logger LOG = LoggerFactory.getLogger(BookService.class);

​

​

  private final WebClient webClient;

  private final ReactiveCircuitBreaker readingListCircuitBreaker;

​

  public BookService(ReactiveCircuitBreakerFactory circuitBreakerFactory) {

    this.webClient = WebClient.builder().baseUrl("http://localhost:8090").build();

    this.readingListCircuitBreaker = circuitBreakerFactory.create("recommended");

  }

​

  public Mono<String> readingList() {

    return readingListCircuitBreaker.run(webClient.get().uri("/recommended").retrieve().bodyToMono(String.class), throwable -> {

      LOG.warn("Error making request to book service", throwable);

      return Mono.just("Cloud Native Java (O'Reilly)");

    });

  }

}

https://blog.codecentric.de/resilience-design-patterns-retry-fallback-timeout-circuit-breaker