带有功能区的 Spring Cloud 不会忽略服务器答案

【问题标题】：Spring cloud with ribbon not ignoring down servers带有功能区的 Spring Cloud 不会忽略服务器
【发布时间】：2017-08-04 17:23:23
【问题描述】：

我在使用 eureka 进行客户端负载平衡方面遵循 spring 指南：

https://spring.io/guides/gs/client-side-load-balancing/

但是在我关闭了 3 个服务器实例后，我收到了连接拒绝异常。客户端并没有忽略 ping 失败的服务器，而是仍在尝试向这些服务器发送请求。当这些服务器被 ping 时，我得到一个异常，当我的客户端尝试向这些服务器发送请求时，我得到了同样的异常。似乎功能区正在通过配置中列出的所有服务器执行某种盲循环，它忽略了我关闭的服务器。

application.yml

spring:
  application:
    name: user

server:
  port: 8888

say-hello:
  ribbon:
    eureka:
      enabled: false
    listOfServers: localhost:8090,localhost:9092,localhost:9999
    ServerListRefreshInterval: 15000

SayHelloConfiguration.java

package hello;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Bean;

import com.netflix.client.config.IClientConfig;
import com.netflix.loadbalancer.IPing;
import com.netflix.loadbalancer.IRule;
import com.netflix.loadbalancer.PingUrl;
import com.netflix.loadbalancer.AvailabilityFilteringRule;

public class SayHelloConfiguration {

    @Autowired
    IClientConfig ribbonClientConfig;

    @Bean
    public IPing ribbonPing(IClientConfig config) {
        return new PingUrl();
    }

    @Bean
    public IRule ribbonRule(IClientConfig config) {
        return new AvailabilityFilteringRule();
    }

}

UserApplication.java

package hello;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Bean;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.client.RestTemplate;
import org.springframework.cloud.client.loadbalancer.LoadBalanced;
import org.springframework.cloud.netflix.ribbon.RibbonClient;

@SpringBootApplication
@RestController
@RibbonClient(name = "say-hello", configuration = SayHelloConfiguration.class)
public class UserApplication {

    @LoadBalanced
    @Bean
    RestTemplate restTemplate(){
        return new RestTemplate();
    }

    @Autowired
    RestTemplate restTemplate;

    @RequestMapping("/hi")
    public String hi(@RequestParam(value="name", defaultValue="Artaban") String name) {
        String greeting = this.restTemplate.getForObject("http://say-hello/greeting", String.class);
        return String.format("%s, %s!", greeting, name);
    }

    public static void main(String[] args) {
        SpringApplication.run(UserApplication.class, args);
    }
}

pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>hello</groupId>
    <artifactId>user</artifactId>
    <version>1.0-SNAPSHOT</version>
    <packaging>jar</packaging>

    <name>user</name>
    <description>Demo project for Spring Boot</description>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>1.5.2.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <java.version>1.8</java.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-ribbon</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>Camden.SR5</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

    <repositories>
        <repository>
            <id>spring-snapshots</id>
            <name>Spring Snapshots</name>
            <url>https://repo.spring.io/snapshot</url>
            <snapshots>
                <enabled>true</enabled>
            </snapshots>
        </repository>
        <repository>
            <id>spring-milestones</id>
            <name>Spring Milestones</name>
            <url>https://repo.spring.io/milestone</url>
            <snapshots>
                <enabled>false</enabled>
            </snapshots>
        </repository>
    </repositories>

</project>

这是我在 ping 关闭服务器时遇到的异常：

java.net.ConnectException: Connection refused: connect
    at java.net.DualStackPlainSocketImpl.connect0(Native Method)
    at java.net.DualStackPlainSocketImpl.socketConnect(DualStackPlainSocketImpl.java:79)
    at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:350)
    at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:206)
    at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:188)
    at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:172)
    at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392)
    at java.net.Socket.connect(Socket.java:589)
    at org.apache.http.conn.scheme.PlainSocketFactory.connectSocket(PlainSocketFactory.java:121)
    at org.apache.http.impl.conn.DefaultClientConnectionOperator.openConnection(DefaultClientConnectionOperator.java:180)
    at org.apache.http.impl.conn.ManagedClientConnectionImpl.open(ManagedClientConnectionImpl.java:326)
    at org.apache.http.impl.client.DefaultRequestDirector.tryConnect(DefaultRequestDirector.java:610)
    at org.apache.http.impl.client.DefaultRequestDirector.execute(DefaultRequestDirector.java:445)
    at org.apache.http.impl.client.AbstractHttpClient.doExecute(AbstractHttpClient.java:835)
    at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:83)
    at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:108)
    at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:56)
    at com.netflix.loadbalancer.PingUrl.isAlive(PingUrl.java:126)
    at com.netflix.loadbalancer.BaseLoadBalancer$SerialPingStrategy.pingServers(BaseLoadBalancer.java:927)
    at com.netflix.loadbalancer.BaseLoadBalancer$Pinger.runPinger(BaseLoadBalancer.java:676)
    at com.netflix.loadbalancer.BaseLoadBalancer$PingTask.run(BaseLoadBalancer.java:629)
    at java.util.TimerThread.mainLoop(Timer.java:555)
    at java.util.TimerThread.run(Timer.java:505)

这是我在客户端应用程序向停机服务器发送请求时遇到的异常：

java.net.ConnectException: Connection refused: connect
    at java.net.DualStackPlainSocketImpl.connect0(Native Method) ~[na:1.8.0_101]
    at java.net.DualStackPlainSocketImpl.socketConnect(DualStackPlainSocketImpl.java:79) ~[na:1.8.0_101]
    at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:350) ~[na:1.8.0_101]
    at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:206) ~[na:1.8.0_101]
    at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:188) ~[na:1.8.0_101]
    at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:172) ~[na:1.8.0_101]
    at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392) ~[na:1.8.0_101]
    at java.net.Socket.connect(Socket.java:589) ~[na:1.8.0_101]
    at java.net.Socket.connect(Socket.java:538) ~[na:1.8.0_101]
    at sun.net.NetworkClient.doConnect(NetworkClient.java:180) ~[na:1.8.0_101]
    at sun.net.www.http.HttpClient.openServer(HttpClient.java:432) ~[na:1.8.0_101]
    at sun.net.www.http.HttpClient.openServer(HttpClient.java:527) ~[na:1.8.0_101]
    at sun.net.www.http.HttpClient.<init>(HttpClient.java:211) ~[na:1.8.0_101]
    at sun.net.www.http.HttpClient.New(HttpClient.java:308) ~[na:1.8.0_101]
    at sun.net.www.http.HttpClient.New(HttpClient.java:326) ~[na:1.8.0_101]
    at sun.net.www.protocol.http.HttpURLConnection.getNewHttpClient(HttpURLConnection.java:1169) ~[na:1.8.0_101]
    at sun.net.www.protocol.http.HttpURLConnection.plainConnect0(HttpURLConnection.java:1105) ~[na:1.8.0_101]
    at sun.net.www.protocol.http.HttpURLConnection.plainConnect(HttpURLConnection.java:999) ~[na:1.8.0_101]
    at sun.net.www.protocol.http.HttpURLConnection.connect(HttpURLConnection.java:933) ~[na:1.8.0_101]
    at org.springframework.http.client.SimpleBufferingClientHttpRequest.executeInternal(SimpleBufferingClientHttpRequest.java:78) ~[spring-web-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at org.springframework.http.client.AbstractBufferingClientHttpRequest.executeInternal(AbstractBufferingClientHttpRequest.java:48) ~[spring-web-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at org.springframework.http.client.AbstractClientHttpRequest.execute(AbstractClientHttpRequest.java:53) ~[spring-web-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at org.springframework.http.client.InterceptingClientHttpRequest$InterceptingRequestExecution.execute(InterceptingClientHttpRequest.java:99) ~[spring-web-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at org.springframework.cloud.client.loadbalancer.LoadBalancerRequestFactory$1.apply(LoadBalancerRequestFactory.java:63) ~[spring-cloud-commons-1.1.7.RELEASE.jar:1.1.7.RELEASE]
    at org.springframework.cloud.client.loadbalancer.LoadBalancerRequestFactory$1.apply(LoadBalancerRequestFactory.java:52) ~[spring-cloud-commons-1.1.7.RELEASE.jar:1.1.7.RELEASE]
    at org.springframework.cloud.netflix.ribbon.RibbonLoadBalancerClient.execute(RibbonLoadBalancerClient.java:98) ~[spring-cloud-netflix-core-1.2.5.RELEASE.jar:1.2.5.RELEASE]
    at org.springframework.cloud.client.loadbalancer.RetryLoadBalancerInterceptor$1.doWithRetry(RetryLoadBalancerInterceptor.java:88) ~[spring-cloud-commons-1.1.7.RELEASE.jar:1.1.7.RELEASE]
    at org.springframework.cloud.client.loadbalancer.RetryLoadBalancerInterceptor$1.doWithRetry(RetryLoadBalancerInterceptor.java:76) ~[spring-cloud-commons-1.1.7.RELEASE.jar:1.1.7.RELEASE]
    at org.springframework.retry.support.RetryTemplate.doExecute(RetryTemplate.java:286) ~[spring-retry-1.2.0.RELEASE.jar:na]
    at org.springframework.retry.support.RetryTemplate.execute(RetryTemplate.java:163) ~[spring-retry-1.2.0.RELEASE.jar:na]
    at org.springframework.cloud.client.loadbalancer.RetryLoadBalancerInterceptor.intercept(RetryLoadBalancerInterceptor.java:76) ~[spring-cloud-commons-1.1.7.RELEASE.jar:1.1.7.RELEASE]
    at org.springframework.http.client.InterceptingClientHttpRequest$InterceptingRequestExecution.execute(InterceptingClientHttpRequest.java:86) ~[spring-web-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at org.springframework.http.client.InterceptingClientHttpRequest.executeInternal(InterceptingClientHttpRequest.java:70) ~[spring-web-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at org.springframework.http.client.AbstractBufferingClientHttpRequest.executeInternal(AbstractBufferingClientHttpRequest.java:48) ~[spring-web-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at org.springframework.http.client.AbstractClientHttpRequest.execute(AbstractClientHttpRequest.java:53) ~[spring-web-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at org.springframework.web.client.RestTemplate.doExecute(RestTemplate.java:652) ~[spring-web-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at org.springframework.web.client.RestTemplate.execute(RestTemplate.java:613) ~[spring-web-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at org.springframework.web.client.RestTemplate.getForObject(RestTemplate.java:287) ~[spring-web-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at hello.UserApplication.hi(UserApplication.java:31) ~[classes/:na]
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_101]
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_101]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_101]
    at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_101]
    at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:205) ~[spring-web-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:133) ~[spring-web-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:116) ~[spring-webmvc-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:827) ~[spring-webmvc-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:738) ~[spring-webmvc-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:85) ~[spring-webmvc-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:963) ~[spring-webmvc-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:897) ~[spring-webmvc-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:970) ~[spring-webmvc-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:861) ~[spring-webmvc-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:622) ~[tomcat-embed-core-8.5.11.jar:8.5.11]
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:846) ~[spring-webmvc-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:729) ~[tomcat-embed-core-8.5.11.jar:8.5.11]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:230) ~[tomcat-embed-core-8.5.11.jar:8.5.11]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165) ~[tomcat-embed-core-8.5.11.jar:8.5.11]
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52) ~[tomcat-embed-websocket-8.5.11.jar:8.5.11]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192) ~[tomcat-embed-core-8.5.11.jar:8.5.11]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165) ~[tomcat-embed-core-8.5.11.jar:8.5.11]
    at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:99) ~[spring-web-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192) ~[tomcat-embed-core-8.5.11.jar:8.5.11]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165) ~[tomcat-embed-core-8.5.11.jar:8.5.11]
    at org.springframework.web.filter.HttpPutFormContentFilter.doFilterInternal(HttpPutFormContentFilter.java:105) ~[spring-web-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192) ~[tomcat-embed-core-8.5.11.jar:8.5.11]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165) ~[tomcat-embed-core-8.5.11.jar:8.5.11]
    at org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:81) ~[spring-web-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192) ~[tomcat-embed-core-8.5.11.jar:8.5.11]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165) ~[tomcat-embed-core-8.5.11.jar:8.5.11]
    at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:197) ~[spring-web-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192) ~[tomcat-embed-core-8.5.11.jar:8.5.11]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165) ~[tomcat-embed-core-8.5.11.jar:8.5.11]
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:198) ~[tomcat-embed-core-8.5.11.jar:8.5.11]
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96) [tomcat-embed-core-8.5.11.jar:8.5.11]
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:474) [tomcat-embed-core-8.5.11.jar:8.5.11]
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140) [tomcat-embed-core-8.5.11.jar:8.5.11]
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79) [tomcat-embed-core-8.5.11.jar:8.5.11]
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87) [tomcat-embed-core-8.5.11.jar:8.5.11]
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:349) [tomcat-embed-core-8.5.11.jar:8.5.11]
    at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:783) [tomcat-embed-core-8.5.11.jar:8.5.11]
    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66) [tomcat-embed-core-8.5.11.jar:8.5.11]
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:798) [tomcat-embed-core-8.5.11.jar:8.5.11]
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1434) [tomcat-embed-core-8.5.11.jar:8.5.11]
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) [tomcat-embed-core-8.5.11.jar:8.5.11]
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) [na:1.8.0_101]
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) [na:1.8.0_101]
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) [tomcat-embed-core-8.5.11.jar:8.5.11]
    at java.lang.Thread.run(Thread.java:745) [na:1.8.0_101]

我错过了什么？预期的行为是，在关闭服务器的 ping 失败后，客户端应用程序将忽略这些服务器并且不再向它们发送请求。

谢谢

【问题讨论】：

你是用eureka注册服务吗？如果是，服务实例在您关闭后是否仍显示在 eureka Web 界面中？
我没有使用尤里卡，不。正如您在客户端的 application.yml 中看到的，我使用的是静态服务器列表来连接，本教程的想法只是为了了解 Spring Cloud 中的负载平衡。你认为这个静态的服务器列表有问题吗？考虑到当我关闭任何这些服务器时，客户端会继续 ping 它并向它发送请求。
您在关闭服务器后等待多长时间？
我将 ping 配置为每 15 秒联系一次活动服务器。在我关闭服务器后，下一个 ping 将抛出上面的异常，当我在客户端应用程序中执行请求并且“循环”到达我关闭的服务器时，会抛出另一个异常。在关闭服务器后，我不会等待任何特定时间来执行请求，但我只是在 ping 失败并且行为仍然存在之后才尝试执行此操作。

标签： spring-boot load-balancing spring-cloud spring-cloud-netflix

【解决方案1】：

好的，所以我遇到了这个问题，这就是我尝试解决的方法。不确定这是否是理想的方式，但这似乎足以满足我目前的需求。

IPing 实现仅有助于确定服务器是存活还是死亡。它不会从可用服务器列表中删除该服务器。

根据Javadoc here，看起来 Ribbon 将决定何时将服务器标记为不健康的决定权留给了客户端。这似乎是一个安全的选择。如果服务器在 1 次 ping 与 3 次 ping 失败时标记为不可用，并且 ping 时是否存在退避 - 所有这些都取决于您手头的应用程序类型，因此只有客户端才能确保安全选择。

但是，对于如何在 Spring Cloud Netflix 的上下文中将 ServerStatusChangeListener 添加到负载均衡器，没有明确的指示。所以，我认为如果我们有这种能力，那将是从听众中调用BaseLoadBalancer.markServerDown(Server) 的正确位置。 Spring Cloud 大师 (@spencergibb) 可以在这里发挥作用。

继续我如何实施我的解决方案。除了 IPing，我还配置了一个 IRule，并从 com.netflix.loadbalancer.AvailabilityFilteringRule 扩展了我的规则。由于此规则过滤了电路跳闸的服务器，因此您唯一需要添加的是检查服务器本身是否处于活动状态，然后再将其作为所选服务器返回。

@Configuration
public class MyLoadBalancerConfig {

    @Bean
    public IRule ribbonRule(IClientConfig config) {
        return new AvailabilityBasedServerSelectionRule();
    }

    @Bean
    public IPing ribbonPing() {
        return server -> {
            try {
                // TODO: ping your server to decide if health check has passed or not
                Thread.sleep(2000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }

            return true;
        };
    }

    @Bean
    public ServerList<Server> ribbonServerList(IClientConfig config) {
        return new ServerList<Server>() {
            @Override
            public List<Server> getInitialListOfServers() {
                Server server1 = new Server("server1");
                Server server2 = new Server("server2");
                return new ArrayList<>(Arrays.asList(server1, server2));
            }

            @Override
            public List<Server> getUpdatedListOfServers() {
                Server server3 = new Server("server3");
                Server server4 = new Server("server4");

                return new ArrayList<>(Arrays.asList(server3, server4));
            }
        };
    }
}

和

public class AvailabilityBasedServerSelectionRule extends AvailabilityFilteringRule {

    @Override
    public Server choose(Object key) {

        Server chosenServer = super.choose(key);

        int count = 1;
        List<Server> reachableServers = this.getLoadBalancer().getReachableServers();
        List<Server> allServers = this.getLoadBalancer().getAllServers();

        if(reachableServers.size() > 0) {
            while(!reachableServers.contains(chosenServer) && count++ < allServers.size()) {
                chosenServer = super.choose(key);
            }
        }

        System.out.println("chosenServer.isAlive() = " + chosenServer.isAlive());
        return chosenServer;
    }
}

因此，AvailabilityBasedServerSelectionRule 始终返回活动且未发生电路跳闸的服务器。我还没有发现这种解决方法的任何问题。如果我在继续使用这种方法时发现任何内容，我会更新这篇文章。祝你好运！

【讨论】：

choose 方法每次都会被调用，但是它是如何知道不可访问服务器的呢？ this.getLoadBalancer().getReachableServers();是否保证只返回可用的服务器。我已经实现了您的解决方案，但它仍然向其中一台停机服务器发送请求。
这个答案已经超过 2 年了，我忘记了大部分问题:).. 但是，在我上面的解决方案中 - 在 MyLoadBalancerConfig 的 public IPing ribbonPing() 方法中有一个 TODO。 java类。我认为您需要实施该健康检查以确定您的服务器是否健康并相应地返回响应。

【解决方案2】：

如果下一个服务器不存在，您可以告诉功能区重试：

say-hello:
  ribbon:
    MaxAutoRetriesNextServer: 1

这在使用 eureka 时也有效。由于服务注册表会在服务器未崩溃且未取消注册的情况下删除延迟的服务器。

另外，需要添加如下依赖：

<dependency>
    <groupId>org.springframework.retry</groupId>
    <artifactId>spring-retry</artifactId>
</dependency>

【讨论】：

【解决方案3】：

如教程中所述，这是一个简化的示例：

Ribbon 中的负载均衡器通常从 Netflix Eureka 服务注册中心...为了我们的简单目的，我们跳过了 Eureka

您的应用程序无法知道您的服务器不再可用。这是服务注册中心（例如 eureka）的工作，它可以处理通过心跳机制发现哪些服务是死的或活的......

【讨论】：

那么有一个静态的服务器列表，客户端应用程序总是会尝试向所有服务器发送请求，即使 ping 失败？那么，ping 静态列表中的那些服务器的目的是什么？
这只是教程中给出的一个非常简化的场景，用于演示功能区负载平衡的工作原理。默认情况下，Ribbon 仅执行循环负载平衡。如果你想要更健壮的东西，你应该使用本教程中演示的 eureka spring.io/guides/gs/service-registration-and-discovery

【解决方案4】：

在调试 BaseLoadBalancer 之后，我意识到以下事情： Ribbon ping 列表中的所有服务器实例，并确定其中哪些已死亡。 Ribbon 在 SerialPingStrategy 中执行此操作，这是 IPingStrategy 的默认实现。这些 ping 结果被处理，并且自上次 ping 过程以来状态已更改的服务器列表被发送到 ServerStatusChangeListener 实例（如果其中至少有一些实例存在）。但是在给定的教程中没有提供任何实现。我想如果你提供一些 ServerStatusChangeListener 的实现并将其添加到应用程序上下文中，那么可能会有不同的行为。

【讨论】：

【解决方案5】：

PingUrl 尝试解析服务器是否存在，对于您在属性 listOfServers 中指定的所有服务器：
localhost:8090,localhost:9092,localhost:9999 所以你必须启动所有服务或删除你不需要的服务

就是这样！

【讨论】：