spring-cloud-kubernetes与SpringCloud Gateway

本文是《spring-cloud-kubernetes实战系列》的第五篇，主要内容是在kubernetes上部署一个SpringCloud Gateway应用，该应用使用了spring-cloud-kubernetes框架，可以将请求转发到kubernetes环境中的其他服务上；

系列文章列表

1. 《spring-cloud-kubernetes官方demo运行实战》
2. 《你好spring-cloud-kubernetes》
3. 《spring-cloud-kubernetes背后的三个关键知识点》
4. 《spring-cloud-kubernetes的服务发现和轮询实战(含熔断)》
5. 《spring-cloud-kubernetes与SpringCloud Gateway》
6. 《spring-cloud-kubernetes与k8s的configmap》

本文大纲

接下来的内容由以下几部分组成：

1. 什么是SpringCloud Gateway
2. SpringCloud Gateway实战参考
3. kubernetes上的SpringCloud Gateway
4. 实战环境信息
5. 实战源码下载
6. 开发webdemo
7. 开发k8sgatewaydemo
8. 解决权限问题
9. 最后一个疑问

什么是SpringCloud Gateway

SpringCloud Gateway是SpringCloud技术栈下的网关服务框架，在基于SpringCloud的微服务环境中，外部请求会到达SpringCloud Gateway应用，该应用对请求做转发、过滤、鉴权、熔断等前置操作，一个典型的请求响应流程如下所示：

SpringCloud Gateway实战参考

如果您之前没有使用过SpringCloud Gateway，推荐您阅读《速体验SpringCloud Gateway》，有时间的话动手实战效果更佳，只需编写少量代码就能快速熟悉这个SpringCloud技术栈中非常重要的功能；

kubernetes上的SpringCloud Gateway

注意以下两个知识点：

1. SpringCloud Gateway之所以能将外部请求路由到正确的后台服务上，是因为注册中心的存在，SpringCloud Gateway可以在注册中心取得所有服务的信息，因此它可以根据路径和服务的对应关系，将请求转发到对应的服务上；
2. 如果您看过本系列的上一篇 《spring-cloud-kubernetes的服务发现和轮询实战(含熔断)》，您就知道spring-cloud-kubernetes框架可以获取kubernetes环境内的所有服务（这里说的服务就是kubernetes的service）；

将以上两个知识点结合起来，于是可以推测：<font color="blue">运行在kubernetes环境的SpringCloud Gateway应用，如果使用了spring-cloud-kubernetes框架就能得到kubernetes的service列表，因此可以承担网关的角色，将外部请求转发至kubernetes内的service上，最终到达对应的Pod；</font>

架构如下图所示，请注意黄色背景的对话框，里面标识了关键操作：

至此，理论分析已经完成，我们来实战验证这个理论，接下来我们开发两个java应用：

1. 先开发一个普通的web服务，名为webdemo，提供一个http接口；
2. 再开发一个SpringCloud Gateway应用，名为k8sgatewaydemo；

环境信息

本次实战的环境和版本信息如下：

1. 操作系统：CentOS Linux release 7.6.1810
2. minikube：1.1.1
3. Java：1.8.0_191
4. Maven：3.6.0
5. fabric8-maven-plugin插件：3.5.37
6. spring-cloud-kubernetes：1.0.1.RELEASE
7. spring cloud：Greenwich.SR2
8. springboot：2.1.6.RELEASE

源码下载

如果您不打算写代码，也可以从GitHub上下载本次实战的源码，地址和链接信息如下表所示：

这个git项目中有多个文件夹，本章的两个应用分别在webdemo和k8sgatewaydemo文件夹下；
下图红框中是webdemo应用的源码：

下图红框中是k8sgatewaydemo应用的源码：

下面是详细的编码过程；

开发webdemo

webdemo是个极其普通的spring boot应用，<font color="red">和SpringCloud没有任何关系</font>；

1. webdemo提供一个http接口，将请求header中名为extendtag的参数返回给请求方，controller类如下：

@RestController
@RequestMapping("/hello")
public class HelloController {

    @RequestMapping(value = "time", method = RequestMethod.GET)
    public String hello(HttpServletRequest request){

        return "hello, "
                + new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(new Date())
                + ", extendtag ["
                + request.getHeader("extendtag")
                + "]";
    }
}

1. 启动类WebdemoApplication.java：

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

1. 要注意的是pom.xml，里面通过名为<font color="blue">fabric8-maven-plugin</font>的maven插件，将webdemo快速部署到minikube环境：

<?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>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.1.6.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.bolingcavalry</groupId>
    <artifactId>webdemo</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>webdemo</name>
    <description>Demo project for Spring Boot</description>

    <properties>
        <java.version>1.8</java.version>
        <spring-boot.version>2.1.6.RELEASE</spring-boot.version>
        <fabric8.maven.plugin.version>3.5.37</fabric8.maven.plugin.version>
    </properties>

    <dependencies>
        <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>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <version>${spring-boot.version}</version>
                <executions>
                    <execution>
                        <goals>
                            <goal>repackage</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>

            <plugin>
                <!--skip deploy -->
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-deploy-plugin</artifactId>
                <version>${maven-deploy-plugin.version}</version>
                <configuration>
                    <skip>true</skip>
                </configuration>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-surefire-plugin</artifactId>
                <version>${maven-surefire-plugin.version}</version>
                <configuration>
                    <skipTests>true</skipTests>
                    <!-- Workaround for https://issues.apache.org/jira/browse/SUREFIRE-1588 -->
                    <useSystemClassLoader>false</useSystemClassLoader>
                </configuration>
            </plugin>
            <plugin>
                <groupId>io.fabric8</groupId>
                <artifactId>fabric8-maven-plugin</artifactId>
                <version>${fabric8.maven.plugin.version}</version>
                <executions>
                    <execution>
                        <id>fmp</id>
                        <goals>
                            <goal>resource</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>

    <profiles>
        <profile>
            <id>kubernetes</id>
            <build>
                <plugins>
                    <plugin>
                        <groupId>io.fabric8</groupId>
                        <artifactId>fabric8-maven-plugin</artifactId>
                        <version>${fabric8.maven.plugin.version}</version>
                        <executions>
                            <execution>
                                <id>fmp</id>
                                <goals>
                                    <goal>resource</goal>
                                    <goal>build</goal>
                                </goals>
                            </execution>
                        </executions>
                        <configuration>
                            <enricher>
                                <config>
                                    <fmp-service>
                                        <type>NodePort</type>
                                    </fmp-service>
                                </config>
                            </enricher>
                        </configuration>
                    </plugin>
                </plugins>
            </build>
        </profile>
    </profiles>
</project>

1. 以上就是webdemo应用的内容了，接下来要编译、构建、部署到minikube环境，在pom.xml执行以下命令即可：

mvn clean install fabric8:deploy -Dfabric8.generator.from=fabric8/java-jboss-openjdk8-jdk -Pkubernetes

部署完成后终端输出类似如下成功信息：

[INFO] 
[INFO] <<< fabric8-maven-plugin:3.5.37:deploy (default-cli) < install @ webdemo <<<
[INFO] 
[INFO] 
[INFO] --- fabric8-maven-plugin:3.5.37:deploy (default-cli) @ webdemo ---
[INFO] F8: Using Kubernetes at https://192.168.121.133:8443/ in namespace default with manifest /usr/local/work/k8s/webdemo/target/classes/META-INF/fabric8/kubernetes.yml 
[INFO] Using namespace: default
[INFO] Updating a Service from kubernetes.yml
[INFO] Updated Service: target/fabric8/applyJson/default/service-webdemo.json
[INFO] Using namespace: default
[INFO] Updating Deployment from kubernetes.yml
[INFO] Updated Deployment: target/fabric8/applyJson/default/deployment-webdemo.json
[INFO] F8: HINT: Use the command `kubectl get pods -w` to watch your pods start up
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  11.804 s
[INFO] Finished at: 2019-07-07T21:32:26+08:00
[INFO] ------------------------------------------------------------------------

1. 查看service和pod，确认一切正常：

[root@minikube webdemo]# kubectl get service
NAME             TYPE        CLUSTER-IP      EXTERNAL-IP   PORT(S)          AGE
kubernetes       ClusterIP   10.96.0.1       <none>        443/TCP          29d
webdemo          NodePort    10.106.98.137   <none>        8080:30160/TCP   115m
[root@minikube webdemo]# kubectl get pod
NAME                              READY   STATUS    RESTARTS   AGE
webdemo-c9f774b9-gsbgx            1/1     Running   0          3m13s

1. 使用minikube命令取得webdemo服务对外暴露的地址：

[root@minikube webdemo]# minikube service webdemo --url
http://192.168.121.133:30160

可见外部通过地址：http://192.168.121.133:30160 即可访问到webdemo应用；

1. 在浏览器输入地址：http://192.168.121.133:30160/hello/time ，即可验证webdemo的http接口是否正常，如下图，由于header中没有extendtag属性，因此返回的extendtag为null：

至此，webdemo在minikue上已经正常运行，该开发gateway应用了；

开发k8sgatewaydemo

1. 基于maven创建一个名为k8sgatewaydemo的springboot应用，pom.xml内容如下：

<?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>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.1.6.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.bolingcavalry</groupId>
    <artifactId>k8sgatewaydemo</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>k8sgatewaydemo</name>
    <description>Demo project for Spring Boot</description>

    <properties>
        <java.version>1.8</java.version>
        <spring-boot.version>2.1.6.RELEASE</spring-boot.version>
        <maven-checkstyle-plugin.failsOnError>false</maven-checkstyle-plugin.failsOnError>
        <maven-checkstyle-plugin.failsOnViolation>false</maven-checkstyle-plugin.failsOnViolation>
        <maven-checkstyle-plugin.includeTestSourceDirectory>false</maven-checkstyle-plugin.includeTestSourceDirectory>
        <maven-compiler-plugin.version>3.5</maven-compiler-plugin.version>
        <maven-deploy-plugin.version>2.8.2</maven-deploy-plugin.version>
        <maven-failsafe-plugin.version>2.18.1</maven-failsafe-plugin.version>
        <maven-surefire-plugin.version>2.21.0</maven-surefire-plugin.version>
        <fabric8.maven.plugin.version>3.5.37</fabric8.maven.plugin.version>
        <springcloud.kubernetes.version>1.0.1.RELEASE</springcloud.kubernetes.version>
        <spring-cloud.version>Greenwich.SR2</spring-cloud.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-gateway</artifactId>
        </dependency>

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

        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-kubernetes-core</artifactId>
            <version>${springcloud.kubernetes.version}</version>
        </dependency>

        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-kubernetes-discovery</artifactId>
            <version>${springcloud.kubernetes.version}</version>
        </dependency>

        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-kubernetes-ribbon</artifactId>
            <version>${springcloud.kubernetes.version}</version>
        </dependency>

        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-commons</artifactId>
        </dependency>

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

        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-ribbon</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-hystrix</artifactId>
        </dependency>
    </dependencies>

    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>${spring-cloud.version}</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <version>${spring-boot.version}</version>
                <executions>
                    <execution>
                        <goals>
                            <goal>repackage</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>

            <plugin>
                <!--skip deploy -->
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-deploy-plugin</artifactId>
                <version>${maven-deploy-plugin.version}</version>
                <configuration>
                    <skip>true</skip>
                </configuration>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-surefire-plugin</artifactId>
                <version>${maven-surefire-plugin.version}</version>
                <configuration>
                    <skipTests>true</skipTests>
                    <!-- Workaround for https://issues.apache.org/jira/browse/SUREFIRE-1588 -->
                    <useSystemClassLoader>false</useSystemClassLoader>
                </configuration>
            </plugin>
            <plugin>
                <groupId>io.fabric8</groupId>
                <artifactId>fabric8-maven-plugin</artifactId>
                <version>${fabric8.maven.plugin.version}</version>
                <executions>
                    <execution>
                        <id>fmp</id>
                        <goals>
                            <goal>resource</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>

    <profiles>
        <profile>
            <id>kubernetes</id>
            <build>
                <plugins>
                    <plugin>
                        <groupId>io.fabric8</groupId>
                        <artifactId>fabric8-maven-plugin</artifactId>
                        <version>${fabric8.maven.plugin.version}</version>
                        <executions>
                            <execution>
                                <id>fmp</id>
                                <goals>
                                    <goal>resource</goal>
                                    <goal>build</goal>
                                </goals>
                            </execution>
                        </executions>
                        <configuration>
                            <enricher>
                                <config>
                                    <fmp-service>
                                        <type>NodePort</type>
                                    </fmp-service>
                                </config>
                            </enricher>
                        </configuration>
                    </plugin>
                </plugins>
            </build>
        </profile>
    </profiles>
</project>

上述pom文件中有以下几点需要注意：
第一、 依赖spring-cloud-kubernetes-core和spring-cloud-kubernetes-discovery，这样能用到spring-cloud-kubernetes提供的服务发现能力；
第二、依赖spring-cloud-starter-gateway，这样能用上SpringCloud的gateway能力；
第三、不要依赖spring-boot-starter-web，会和spring-cloud-starter-gateway冲突，启动时抛出以下异常：

2019-07-06 08:12:09.188  WARN 1 --- [           main] ConfigServletWebServerApplicationContext : 
Exception encountered during context initialization - 
cancelling refresh attempt: 
org.springframework.beans.factory.UnsatisfiedDependencyException: 
Error creating bean with name 'routeDefinitionRouteLocator' defined in class path resource [org/springframework/cloud/gateway/config/GatewayAutoConfiguration.class]: 
Unsatisfied dependency expressed through method 'routeDefinitionRouteLocator' parameter 1; 
nested exception is org.springframework.beans.factory.UnsatisfiedDependencyException: 
Error creating bean with name 'modifyRequestBodyGatewayFilterFactory' defined in class path resource [org/springframework/cloud/gateway/config/GatewayAutoConfiguration.class]: 
Unsatisfied dependency expressed through method 'modifyRequestBodyGatewayFilterFactory' parameter 0; 
nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type 'org.springframework.http.codec.ServerCodecConfigurer' available: 
expected at least 1 bean which qualifies as autowire candidate. Dependency annotations: {}

1. 开发SpringCloud Gateway的启动类K8sgatewaydemoApplication.java，里面也包含了网关路由配置的实例化，除了配置路径和转发服务的关系，还在请求的header中添加了extendtag属性，请注意注释的内容：

@SpringBootApplication
@EnableDiscoveryClient
public class K8sgatewaydemoApplication {

    public static void main(String[] args) {
        SpringApplication.run(K8sgatewaydemoApplication.class, args);
    }

    @Bean
    public RouteLocator customRouteLocator(RouteLocatorBuilder builder) {
        return builder.routes()
                //增加一个path匹配，以"/customize/hello/"开头的请求都在此路由
                .route(r -> r.path("/customize/hello/**")
                        //表示将路径中的第一级参数删除，用剩下的路径与webdemo的路径做拼接，
                        //这里就是"lb://webdemo/hello/"，能匹配到webdemo的HelloController的路径
                        .filters(f -> f.stripPrefix(1)
                                //在请求的header中添加一个key&value
                                .addRequestHeader("extendtag", "geteway-" + System.currentTimeMillis()))
                        //指定匹配服务webdemo，lb是load balance的意思
                        .uri("lb://webdemo")
                ).build();
    }
}

从上述代码可见，K8sgatewaydemoApplication与普通环境下的SpringCloud Gateway并无差别，都是通过EnableDiscoveryClient注解获取服务列表，配置RouteLocator实现路由逻辑；

1. 配置文件application.yml的内容：

spring:
  application:
    name: gateway
  cloud:
    gateway:
      discovery:
        locator:
          enabled: true
          lowerCaseServiceId: true

1. 以上就是k8sgatewaydemo应用的内容了，接下来要编译、构建、部署到minikube环境，在pom.xml执行以下命令即可：

mvn clean install fabric8:deploy -Dfabric8.generator.from=fabric8/java-jboss-openjdk8-jdk -Pkubernetes

部署完成后终端输出类似如下成功信息：

[INFO] 
[INFO] <<< fabric8-maven-plugin:3.5.37:deploy (default-cli) < install @ k8sgatewaydemo <<<
[INFO] 
[INFO] 
[INFO] --- fabric8-maven-plugin:3.5.37:deploy (default-cli) @ k8sgatewaydemo ---
[INFO] F8: Using Kubernetes at https://192.168.121.133:8443/ in namespace default with manifest /usr/local/work/k8s/k8sgatewaydemo/target/classes/META-INF/fabric8/kubernetes.yml 
[INFO] Using namespace: default
[INFO] Updating a Service from kubernetes.yml
[INFO] Updated Service: target/fabric8/applyJson/default/service-k8sgatewaydemo.json
[INFO] Using namespace: default
[INFO] Updating Deployment from kubernetes.yml
[INFO] Updated Deployment: target/fabric8/applyJson/default/deployment-k8sgatewaydemo.json
[INFO] F8: HINT: Use the command `kubectl get pods -w` to watch your pods start up
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  16.538 s
[INFO] Finished at: 2019-07-07T22:04:48+08:00
[INFO] ------------------------------------------------------------------------

1. 查看service和pod，确认一切正常：

[root@minikube k8sgatewaydemo]# clear
[root@minikube k8sgatewaydemo]# kubectl get service
NAME             TYPE        CLUSTER-IP      EXTERNAL-IP   PORT(S)          AGE
k8sgatewaydemo   NodePort    10.97.94.238    <none>        8080:31352/TCP   129m
kubernetes       ClusterIP   10.96.0.1       <none>        443/TCP          29d
webdemo          NodePort    10.106.98.137   <none>        8080:30160/TCP   145m
[root@minikube k8sgatewaydemo]# kubectl get pod
NAME                              READY   STATUS    RESTARTS   AGE
k8sgatewaydemo-6fbb79885c-r2jfn   1/1     Running   0          33s
webdemo-c9f774b9-gsbgx            1/1     Running   0          32m

1. 使用minikube命令取得webdemo服务对外暴露的地址：

[root@minikube k8sgatewaydemo]# minikube service k8sgatewaydemo --url
http://192.168.121.133:31352

可见外部通过地址：http://192.168.121.133:31352 即可访问到k8sgatewaydemo应用；

1. 在浏览器输入地址：http://192.168.121.133:31352/customize/hello/time ，即可验证k8sgatewaydemo作为网关应用，能否将路径中带有<font color="blue">customize</font>的请求转发到webdemo应用，并且在请求header中添加名为entendtag的属性，如下图，浏览器展示的内容是webdemo的http接口返回的，并且extendtag的内容也不为空了，而是k8sgatewaydemo在转发前写入的：

上述结果表明已可以证明我们之前的推测是正确的：SpringCloud Gateway应用在使用了spring-cloud-kubernetes提供的注册发现能力后，可以将请求转发到kubernetes环境中的服务上；
也就是说，借助spring-cloud-kubernetes框架，你在SpringCloud环境开发的SpringCloud Gateway应用，可以以很小的代价迁移到kubernetes环境，与kubernetes环境中的service可以很好的交互，而原有的eureka注册中心也可以不用了；

解决权限问题

如果您的spring-cloud-kubernetes在向webdemo转发请求时抛出以下错误，那是因为遇到了kubernetes的权限问题：

2019-07-06 04:46:40.042  WARN 1 --- [erListUpdater-1] c.n.l.PollingServerListUpdater           : Failed one update cycle
io.fabric8.kubernetes.client.KubernetesClientException: Failure executing: GET at: https://10.96.0.1/api/v1/namespaces/default/endpoints/account-service. Message: Forbidden!Configured service account doesn't have access. Service account may have been revoked. endpoints "account-service" is forbidden: User "system:serviceaccount:default:default" cannot get resource "endpoints" in API group "" in the namespace "default".
        at io.fabric8.kubernetes.client.dsl.base.OperationSupport.requestFailure(OperationSupport.java:476) ~[kubernetes-client-4.1.0.jar!/:na]
        at io.fabric8.kubernetes.client.dsl.base.OperationSupport.assertResponseCode(OperationSupport.java:413) ~[kubernetes-client-4.1.0.jar!/:na]
        at io.fabric8.kubernetes.client.dsl.base.OperationSupport.handleResponse(OperationSupport.java:381) ~[kubernetes-client-4.1.0.jar!/:na]
        at io.fabric8.kubernetes.client.dsl.base.OperationSupport.handleResponse(OperationSupport.java:344) ~[kubernetes-client-4.1.0.jar!/:na]
        at io.fabric8.kubernetes.client.dsl.base.OperationSupport.handleGet(OperationSupport.java:313) ~[kubernetes-client-4.1.0.jar!/:na]
        at io.fabric8.kubernetes.client.dsl.base.OperationSupport.handleGet(OperationSupport.java:296) ~[kubernetes-client-4.1.0.jar!/:na]
        at io.fabric8.kubernetes.client.dsl.base.BaseOperation.handleGet(BaseOperation.java:794) ~[kubernetes-client-4.1.0.jar!/:na]
        at io.fabric8.kubernetes.client.dsl.base.BaseOperation.getMandatory(BaseOperation.java:210) ~[kubernetes-client-4.1.0.jar!/:na]


        at io.fabric8.kubernetes.client.dsl.base.BaseOperation.get(BaseOperation.java:177) ~[kubernetes-client-4.1.0.jar!/:na]
        at org.springframework.cloud.kubernetes.ribbon.KubernetesServerList


.getUpdatedListOfServers(KubernetesServerList.java:75) ~[spring-cloud-kubernetes-ribbon-1.0.1.RELEASE.jar!/:1.0.1.RELEASE]
        at com.netflix.loadbalancer.DynamicServerListLoadBalancer.updateListOfServers(DynamicServerListLoadBalancer.java:240) ~[ribbon-loadbalancer-2.3.0.jar!/:2.3.0]
        at com.netflix.loadbalancer.DynamicServerListLoadBalancer$1.doUpdate(DynamicServerListLoadBalancer.java:62) ~[ribbon-loadbalancer-2.3.0.jar!/:2.3.0]
        at com.netflix.loadbalancer.PollingServerListUpdater$1.run(PollingServerListUpdater.java:116) ~[ribbon-loadbalancer-2.3.0.jar!/:2.3.0]
        at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) [na:1.8.0_191]
        at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:308) [na:1.8.0_191]
        at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$301(ScheduledThreadPoolExecutor.java:180) [na:1.8.0_191]
        at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:294) [na:1.8.0_191]
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) [na:1.8.0_191]
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) [na:1.8.0_191]
        at java.lang.Thread.run(Thread.java:748) [na:1.8.0_191]

处理方法是创建ServiceAccount对象，步骤如下：

1. 创建名为<font color="blue">fabric8-rbac.yaml</font>的文件，内容如下：

# NOTE: The service account `default:default` already exists in k8s cluster.
# You can create a new account following like this:
#---
#apiVersion: v1
#kind: ServiceAccount
#metadata:
#  name: <new-account-name>
#  namespace: <namespace>

---
apiVersion: rbac.authorization.k8s.io/v1beta1
kind: ClusterRoleBinding
metadata:
  name: fabric8-rbac
subjects:
  - kind: ServiceAccount
    # Reference to upper's `metadata.name`
    name: default
    # Reference to upper's `metadata.namespace`
    namespace: default
roleRef:
  kind: ClusterRole
  name: cluster-admin
  apiGroup: rbac.authorization.k8s.io

1. 执行以下命令即可创建ServiceAccount对象：

kubectl apply -f fabric8-rbac.yaml

1. 再在浏览器上继续刚才的验证，可以操作成功；

最后一个疑问

再回顾一下k8sgatewaydemo的开发过程，您会发现除了依赖spring-cloud-kubernetes对应的maven库，我们并没有显式调用spring-cloud-kubernetes相关的API或者做相关配置，就获取了所在kubernetes环境的原生服务，这是怎么回事呢？为何成本如此的低？
答案就在《spring-cloud-kubernetes背后的三个关键知识点》一文中，推荐您回顾一下此文。

至此，spring-cloud-kubernetes框架下的SpringCloud Gateway开发实战就完成了，希望本文能帮助您更好的理解和使用spring-cloud-kubernetes，更加高效的将应用向容器化迁移。

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