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spring-boot - 如何在 Spring Boot 中将 Resilience4j 断路器与 WebFlux 一起使用

问题描述

我有调用下游服务 B 的服务 A。

服务 A 代码

@RestController
@RequestMapping(value = "", produces = MediaType.APPLICATION_JSON_VALUE)
public class GreetingController {

    private final GreetingService greetingService;

    public GreetingController(GreetingService greetingService){
        this.greetingService = greetingService;
    }

    @GetMapping(value = "/greetings")
    public Mono<String> getGreetings() {
        return greetingService.callServiceB();
    }
}

@Component
@RequiredArgsConstructor
public class GreetingService {
    
    CircuitBreaker circuitBreaker = CircuitBreaker.ofDefaults("greetingService");
    Callable<Mono<String>> callable = CircuitBreaker.decorateCallable(circuitBreaker, this::clientCall);
    Future<Mono<String>> future = Executors.newSingleThreadExecutor().submit(callable);

    public Mono<String> callServiceB() {
        try {
            return future.get();
        } catch (CircuitBreakerOpenException | InterruptedException | ExecutionException ex){
            return Mono.just("Service is down!");
        }
    }


    private final String url = "/v1/holidaysgreetings";
    
    private Mono<String> clientCall(){
        WebClient client = WebClient.builder().baseUrl("http://localhost:8080").build();
        
        return client
                .get()
                .uri(url)
                .retrieve()
                .bodyToMono(String.class);
}

当我关闭下游服务 B（在 localhost:8080 上运行）并/greetings在课堂上点击端点GreetingsController以查看我的断路器是否正常工作时，我得到了这个令人讨厌的错误

2021-06-28 21:27:31.431 ERROR 10285 --- [nio-8081-exec-7] o.a.c.c.C.[.[.[.[dispatcherServlet]: Servlet.service() for servlet [dispatcherServlet] in context with path [/v1/holidaysgreetings] 
threw exception [Request processing failed; nested exception is org.springframework.web.reactive.function.client.WebClientRequestException: Connection refused: localhost/127.0.0.1:8080; 
nested exception is io.netty.channel.AbstractChannel$AnnotatedConnectException: Connection refused: localhost/127.0.0.1:8080] with root cause

java.net.ConnectException: Connection refused

任何人都知道我为什么会得到这个？我在这里缺少什么？我是否正确实施断路器？

标签： spring-bootspring-webfluxcircuit-breakerresilience4j

解决方案

您将反应式库与常规的非反应式库混合在一起。如果您打算使用spring-webflux它，最好将其reactor-resilience4j与常规reactor-adapter库一起使用。

使用这些导入：

implementation 'org.springframework.boot:spring-boot-starter-webflux'
implementation 'org.springframework.cloud:spring-cloud-starter-circuitbreaker-reactor-resilience4j'
implementation "io.projectreactor.addons:reactor-adapter:${reactorVersion}"

您也没有创建您可以依赖的断路器服务。创建它后，您可以调用“ Mono run(Mono toRun, Function<Throwable, Mono> fallback) ”（如果您愿意，可以调用返回 Flux 的那个）来执行您的服务并提供回退。

这是演示代码中的一个示例。

@RestController
public class CompletableFutureDemoController {

    Logger LOG = LoggerFactory.getLogger(CompletableFutureDemoController.class);

    private CompletableFutureHttpBinService httpBin;
    private ReactiveCircuitBreakerFactory reactiveCircuitBreakerFactory;

    public CompletableFutureDemoController(CompletableFutureHttpBinService httpBin, ReactiveCircuitBreakerFactory reactiveCircuitBreakerFactory) {
        this.httpBin = httpBin;
        this.reactiveCircuitBreakerFactory = reactiveCircuitBreakerFactory;
    }

    @GetMapping("/completablefuture/delay/{seconds}")
    public Mono<Map> delay(@PathVariable int seconds) {
        return reactiveCircuitBreakerFactory.create("completablefuturedelay")
            .run(Mono.fromFuture(httpBin.delay(seconds)), t -> {
                LOG.warn("delay call failed error", t);
                Map<String, String> fallback = new HashMap();
                fallback.put("hello", "world");
                return Mono.just(fallback);
            }
        );
    }
}

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