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你好spring-cloud-kubernetes

关于spring-cloud-kubernetes

spring-cloud-kubernetes是springcloud官方推出的开源项目,用于将Spring Cloud和Spring Boot应用运行在kubernetes环境,并且提供了通用的接口来调用kubernetes服务,GitHub上官方地址是:https://github.com/spring-cloud/spring-cloud-kubernetes

该项目的提交者之一,就是SpringCloud的作者之一Spencer Gibb:
在这里插入图片描述

系列文章列表

本文是《spring-cloud-kubernetes实战系列》的第二篇,全文链接如下:

  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》

通过官方demo来了解spring-cloud-kubernetes

spring-cloud-kubernetes项目也提供了丰富的官方demo来帮助开发者了解和学习spring-cloud-kubernetes,您可以参考《spring-cloud-kubernetes官方demo运行实战》快速体验官方demo;

实战spring-cloud-kubernetes

今天实战的内容是开发一个简单的java应用,然后将其部署在kubernetes环境(minikube 1.1.1),该应用通过spring-cloud-kubernetes调用当前kubernetes的服务;

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

上面的linux、minikube、java、maven,请确保已准备好,linux环境下minikube的安装和启动请参考《Linux安装minikube指南 》

准备工作已经OK,开始编码吧。

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:

名称 链接 备注
项目主页 https://github.com/zq2599/blog_demos 该项目在GitHub上的主页
git仓库地址(https) https://github.com/zq2599/blog_demos.git 该项目源码的仓库地址,https协议
git仓库地址(ssh) git@github.com:zq2599/blog_demos.git 该项目源码的仓库地址,ssh协议

这个git项目中有多个文件夹,本章源码在springcloudk8sdiscovery这个文件夹下,如下图红框所示:
在这里插入图片描述

开发应用

  1. 基于maven创建一个springboot应用,名为springcloudk8sdiscovery
  2. 该应用完整的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>2.1.1.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.bolingcavalry</groupId>
    <artifactId>springcloudk8sdiscovery</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>springcloudk8sdiscovery</name>
    <description>Demo project for Spring Boot</description>

    <properties>
        <java.version>1.8</java.version>
        <spring-boot.version>2.1.1.RELEASE</spring-boot.version>
        <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>
    </properties>

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

    <dependencies>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-kubernetes-core</artifactId>
            <version>1.0.1.RELEASE</version>
        </dependency>

        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-kubernetes-discovery</artifactId>
            <version>1.0.1.RELEASE</version>
        </dependency>

        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-commons</artifactId>
            <version>2.1.1.RELEASE</version>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter</artifactId>
            <version>2.1.1.RELEASE</version>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
            <version>2.1.1.RELEASE</version>
        </dependency>

        <!--
            We need that(actuator) so that it can be used in readiness probes.
            Readiness checks are needed by arquillian, so that it
            knows when to run the actual test.
        -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-actuator</artifactId>
            <version>2.1.1.RELEASE</version>
        </dependency>

        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>fastjson</artifactId>
            <version>1.2.28</version>
        </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>${fabric8.maven.plugin.version}</version>
                        <executions>
                            <execution>
                                <id>fmp</id>
                                <goals>
                                    <goal>resource</goal>
                                    <goal>build</goal>
                                </goals>
                            </execution>
                        </executions>
                        <configuration>
                            <enricher>
                                <config>
                                    <fmp-service>
                                        <type>NodePort</type>
                                    </fmp-service>
                                </config>
                            </enricher>
                        </configuration>
                    </plugin>
                </plugins>
            </build>
        </profile>
        <profile>
            <id>release</id>
            <build>
                <plugins>
                    <plugin>
                        <groupId>io.fabric8</groupId>
                        <artifactId>fabric8-maven-plugin</artifactId>
                        <version>${fabric8.maven.plugin.version}</version>
                        <executions>
                            <execution>
                                <id>fmp</id>
                                <goals>
                                    <goal>resource</goal>
                                    <goal>helm</goal>
                                </goals>
                            </execution>
                        </executions>
                    </plugin>
                </plugins>
            </build>
        </profile>

        <profile>
            <id>integration</id>
            <build>
                <plugins>
                    <plugin>
                        <groupId>io.fabric8</groupId>
                        <artifactId>fabric8-maven-plugin</artifactId>
                        <version>${fabric8.maven.plugin.version}</version>
                        <executions>
                            <execution>
                                <id>fmp</id>
                                <goals>
                                    <goal>resource</goal>
                                    <goal>build</goal>
                                </goals>
                            </execution>
                        </executions>
                    </plugin>
                    <plugin>
                        <groupId>org.apache.maven.plugins</groupId>
                        <artifactId>maven-failsafe-plugin</artifactId>
                        <version>${maven-failsafe-plugin.version}</version>
                        <executions>
                            <execution>
                                <id>run-integration-tests</id>
                                <phase>integration-test</phase>
                                <goals>
                                    <goal>integration-test</goal>
                                    <goal>verify</goal>
                                </goals>
                            </execution>
                        </executions>
                        <configuration>
                            <skipTests>false</skipTests>
                            <skipITs>false</skipITs>
                        </configuration>
                    </plugin>
                </plugins>
            </build>
        </profile>
    </profiles>
</project>

上述pom.xml文件有几处需要关注:
a. 直接依赖了spring-cloud-kubernetes的以下两个库,后面才能使用spring-cloud-kubernetes的服务:

org.springframework.cloud:spring-cloud-kubernetes-core:1.0.1.RELEASE
org.springframework.cloud:spring-cloud-kubernetes-discovery:1.0.1.RELEASE

b. 使用插件fabric8-maven-plugin来构建镜像并部署到minikube环境:

<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>

c. 为fabric8-maven-plugin插件准备了三个profile,本次实战主要用到kubernetes这个:

<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>
                <!--部署到kubernetes后,会创建一个类型为NodePort的service--> 
                <type>NodePort</type> 
              </fmp-service> 
            </config> 
          </enricher> 
        </configuration> 
      </plugin> 
    </plugins> 
  </build> 
</profile>

以上就是pom.xml的内容了,主要是添加spring-cloud-kubernetes的依赖,以及使用fabric8来构建和部署;

  1. 在application.properties文件中设置应用名称:
spring.application.name=springcloudk8sdiscovery
  1. 创建应用启动类Springcloudk8sdiscoveryApplication,可见这是个很普通的springboot启动类:
package com.bolingcavalry.springcloudk8sdiscovery;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;


@SpringBootApplication
@EnableDiscoveryClient
public class Springcloudk8sdiscoveryApplication {

    public static void main(String[] args) {
        SpringApplication.run(Springcloudk8sdiscoveryApplication.class, args);
    }
}
  1. 创建controller类,对外提供http服务,部署完成后通过这些http服务来验证功能:
@RestController
public class DiscoveryController {

    @Autowired
    private DiscoveryClient discoveryClient;

    /**
     * 探针检查响应类
     * @return
     */
    @RequestMapping("/health")
    public String health() {
        return "health";
    }

    /**
     * 返回远程调用的结果
     * @return
     */
    @RequestMapping("/getservicedetail")
    public String getservicedetail(
            @RequestParam(value = "servicename", defaultValue = "") String servicename) {
        return "Service [" + servicename + "]'s instance list : " + JSON.toJSONString(discoveryClient.getInstances(servicename));
    }

    /**
     * 返回发现的所有服务
     * @return
     */
    @RequestMapping("/services")
    public String services() {
        return this.discoveryClient.getServices().toString()
                + ", "
                + new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(new Date());
    }
}

上述代码有几点需要注意:
a. health方法用于响应kubernetes的探针检查;
b. getservicedetail方法接收名为servicename的参数,然后去服务列表中检查对应的服务对象并返回;
c. services方法返回的是所有服务的名称;

以上就是所有代码了,功能是通过autowire得到DiscoveryClient实例,再调用该实例的API取得服务信息。

接下来我们将应用构建并部署到minikube环境;

编译构建

  1. 请确保当前电脑上java、maven、minikube都是正常的;
  2. 在pom.xml文件所在目录执行以下命令,即可编译构建部署一次性完成:
mvn clean package fabric8:deploy -Pkubernetes

构建成功后,控制台输出信息如下:

...
[INFO] 
[INFO] <<< fabric8-maven-plugin:3.5.37:deploy (default-cli) < install @ springcloudk8sdiscovery <<<
[INFO] 
[INFO] 
[INFO] --- fabric8-maven-plugin:3.5.37:deploy (default-cli) @ springcloudk8sdiscovery ---
[INFO] F8: Using Kubernetes at https://192.168.121.133:8443/ in namespace default with manifest /usr/local/work/demo/springcloudk8sdiscovery/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-springcloudk8sdiscovery.json
[INFO] Using namespace: default
[INFO] Updating Deployment from kubernetes.yml
[INFO] Updated Deployment: target/fabric8/applyJson/default/deployment-springcloudk8sdiscovery.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:  11.207 s
[INFO] Finished at: 2019-06-09T18:50:09+08:00
[INFO] ------------------------------------------------------------------------
  1. 用kubectl命令查看部署和服务,都处于正常状态:
[root@minikube springcloudk8sdiscovery]# kubectl get deployments
NAME                      READY   UP-TO-DATE   AVAILABLE   AGE
springcloudk8sdiscovery   1/1     1            1           75m
[root@minikube springcloudk8sdiscovery]# kubectl get svc
NAME                      TYPE        CLUSTER-IP      EXTERNAL-IP   PORT(S)          AGE
kubernetes                ClusterIP   10.96.0.1       <none>        443/TCP          33h
springcloudk8sdiscovery   NodePort    10.102.167.79   <none>        8080:31583/TCP   75m
  1. 执行命令minikube service springcloudk8sdiscovery --url,得到的是可以从外部访问的服务地址:http://192.168.121.133:31583 ,其中192.168.121.133是宿主机IP地址;
  2. 在浏览器上访问地址http://192.168.121.133:31583/services ,如下图,返回的"所有服务"其实是kubernetes中的所有service:
    在这里插入图片描述
  3. 为了验证当前namespace下的所有服务都能被发现,我们再创建个服务实施,执行以下命令,会创建名为my-tomcat的部署和服务:
kubectl run my-tomcat --image=tomcat:7.0.94-jre7-alpine --replicas=2 --port=8080 \
&& kubectl expose deployment my-tomcat --port=8080 --target-port=8080 --external-ip=192.168.50.7 --type=LoadBalancer

由于下载镜像需要一定时间,所以需要稍作等待;
7. 再去访问地址http://192.168.121.133:31583/services ,如下图,my-tomcat赫然在列:
在这里插入图片描述
8. 访问地址http://192.168.121.133:31583/getservicedetail?servicename=my-tomcat ,会得到名为my-tomcat的服务信息,该信息格式化后的内容如下所示:

[
    {
        "host": "172.17.0.4",
        "instanceId": "91201db9-8aa6-11e9-a5b5-000c29fd2001",
        "metadata": {
            "run": "my-tomcat"
        },
        "port": 8080,
        "scheme": "http://",
        "secure": false,
        "serviceId": "my-tomcat",
        "uri": "http://172.17.0.4:8080"
    },
    {
        "host": "172.17.0.5",
        "instanceId": "91223cda-8aa6-11e9-a5b5-000c29fd2001",
        "metadata": {
            "$ref": "$[0].metadata"
        },
        "port": 8080,
        "scheme": "http://",
        "secure": false,
        "serviceId": "my-tomcat",
        "uri": "http://172.17.0.5:8080"
    }
]

可见spring-cloud-kubernetes的DiscoveryClient服务将kubernetes中的"service"资源与SpringCloud中的服务对应起来了,有了这个DiscoveryClient,我们在kubernetes环境就不需要eureka来做注册发现了,而是直接使用kubernetes的服务机制,此时不得不感慨SpringCloud的对DiscoveryClient的设计是如此的精妙。

至此,spring-cloud-kubernetes的初体验就结束了,通过简单的编码我们的程序在kubernetes环境可以取得service资源的信息,随着学习的深入,我们会用到更多的spring-cloud-kubernetes能力,感谢spring-cloud-kubernetes的设计者,让我们的SpringCloud应用畅游在在kubernetes世界。

疑惑待解

您可能会有些疑惑:上面的代码都是和SpringCloud相关的,和spring-cloud-kubernetes没什么关系呀,为什么程序运行起来后就能取得kubernetes环境中的服务信息呢?
此问题如果不弄清楚,后面的学习很难展开,因为我们都不知道自己的代码与kubernetes环境有什么关系,和kubernetes有没有交互?

来源:https://blog.csdn.net/boling_cavalry/article/details/91351411

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