实例关闭时的 Spring Cloud Gateway 500

Question

我有一个使用 Spring Cloud 负载均衡器（Spring Cloud 版本：Hoxton.SR6）的 Spring Cloud Gateway（eureka 客户端）应用程序，并且我有一个 Spring Boot 应用程序实例（启用了正常关闭的 Spring Boot 2.3，（eureka客户）。

当我关闭 Spring Boot 服务并通过网关执行请求时，网关会抛出 500 错误（连接被拒绝），而不是 503。1-2 分钟后出现 503。

谁能澄清这是否是预期的行为？

似乎问题来自eureka-client（在我的情况下是1.9.21版本） AtomicReference<Applications> localRegionApps 不经常更新

谢谢！

更新： 我决定更深入地检查这个 500 错误。结果是我的系统（ubuntu）如果不使用端口就会报这个错误：

curl -v localhost:9722
 Rebuilt URL to: localhost:9722/
   Trying 127.0.0.1...
 TCP_NODELAY set
 connect to 127.0.0.1 port 9722 failed: Connection refused
 Failed to connect to localhost port 9722: Connection refused
 Closing connection 0

所以我把我的 application.yml:

spring:
  cloud:
    gateway:
      routes:
        - id: my_route
          uri: http://localhost:9722/

然后，当我的请求被路由到 my_route 并且没有应用程序使用 9722 时，我收到错误：

io.netty.channel.AbstractChannel$AnnotatedConnectException: finishConnect(..) failed: Connection refused: localhost/127.0.0.1:9722
    Suppressed: reactor.core.publisher.FluxOnAssembly$OnAssemblyException: 
Error has been observed at the following site(s):
    |_ checkpoint ⇢ org.springframework.cloud.gateway.filter.WeightCalculatorWebFilter [DefaultWebFilterChain]
    |_ checkpoint ⇢ org.springframework.boot.actuate.metrics.web.reactive.server.MetricsWebFilter [DefaultWebFilterChain]
    |_ checkpoint ⇢ HTTP GET "/internal/mail/internal/health-check" [ExceptionHandlingWebHandler]
Stack trace:
Caused by: java.net.ConnectException: finishConnect(..) failed: Connection refused
    at io.netty.channel.unix.Errors.throwConnectException(Errors.java:124)
    at io.netty.channel.unix.Socket.finishConnect(Socket.java:251)
    at io.netty.channel.epoll.AbstractEpollChannel$AbstractEpollUnsafe.doFinishConnect(AbstractEpollChannel.java:672)
    at io.netty.channel.epoll.AbstractEpollChannel$AbstractEpollUnsafe.finishConnect(AbstractEpollChannel.java:649)
    at io.netty.channel.epoll.AbstractEpollChannel$AbstractEpollUnsafe.epollOutReady(AbstractEpollChannel.java:529)
    at io.netty.channel.epoll.EpollEventLoop.processReady(EpollEventLoop.java:465)
    at io.netty.channel.epoll.EpollEventLoop.run(EpollEventLoop.java:378)
    at io.netty.util.concurrent.SingleThreadEventExecutor$4.run(SingleThreadEventExecutor.java:989)
    at io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74)
    at io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30)
    at java.base/java.lang.Thread.run(Thread.java:834)

这似乎是一个意外的异常，因为无法使用断路器或任何网关过滤器来处理它。

是否可以正确处理此错误？在这种情况下我想返回 503

Answer 1

你应该使用Cloud Circuit Breaker。

为此：

1. 在你的 pom 中声明相应的 starter：

   <dependency>
       <groupId>org.springframework.cloud</groupId>
       <artifactId>spring-cloud-starter-circuitbreaker-reactor-resilience4j</artifactId>
    </dependency>
   

2. 在application.yaml中声明断路器

   spring:
     cloud:
       gateway:
         routes:
           - id: my_route
             uri: http://localhost:9722/
             filters:
               - name: CircuitBreaker
                 args:
                   name: myCircuitBreaker
                   fallbackUri: forward:/inCaseOfFailureUseThis
   

3. 声明在失败（例如连接错误）的情况下将调用的端点

   @RequestMapping("/inCaseOfFailureUseThis")
       public Mono<ResponseEntity<String>> inCaseOfFailureUseThis() {
           return Mono.just(ResponseEntity.status(HttpStatus.SERVICE_UNAVAILABLE).body("body for service failure case"));
   }
   

Answer 2

将特定异常映射到特定 HTTP 状态代码的最简单方法之一是提供 org.springframework.boot.web.reactive.error.ErrorAttributes 类型的自定义 bean。这是一个例子：

@Bean
public ErrorAttributes errorAttributes() {
    return new CustomErrorAttributes(httpStatusExceptionTypeMapper);
}

public class CustomErrorAttributes extends DefaultErrorAttributes {
    @Override
    public Map<String, Object> getErrorAttributes(ServerRequest request, ErrorAttributeOptions options) {
        Map<String, Object> attributes = super.getErrorAttributes(request, options);
        Throwable error = getError(request);
        MergedAnnotation<ResponseStatus> responseStatusAnnotation = MergedAnnotations
            .from(error.getClass(), MergedAnnotations.SearchStrategy.TYPE_HIERARCHY).get(ResponseStatus.class);
        HttpStatus errorStatus = determineHttpStatus(error, responseStatusAnnotation);
        attributes.put("status", errorStatus.value());
        return attributes;
    }

    private HttpStatus determineHttpStatus(Throwable error, MergedAnnotation<ResponseStatus> responseStatusAnnotation) {
        if (error instanceof ResponseStatusException) {
            return ((ResponseStatusException) error).getStatus();
        }
        return responseStatusAnnotation.getValue("code", HttpStatus.class).orElseGet(() -> {
           if (error instanceof java.net.ConnectException) {
               return HttpStatus.SERVICE_UNAVAILABLE;
           }
           return HttpStatus.INTERNAL_SERVER_ERROR;
        }
    }
}

Answer 3

尝试定义您的自定义 ErrorWebExceptionHandler。 看： org.springframework.boot.web.reactive.error.ErrorWebExceptionHandler org.springframework.boot.autoconfigure.web.reactive.error.DefaultErrorWebExceptionHandler