欢迎访问我的GitHub

这里分类和汇总了欣宸的全部原创(含配套源码):https://github.com/zq2599/blog_demos

从Eureka server获取服务列表

  • Spring cloud环境中的应用,如果注册到Eureka server,就会从Eureka server获取所有应用的注册信息(也叫服务列表),然后保存到本地,这个操作是周期性的,默认每三十秒一次;

  • 以下是来自官方的架构图,可以看到Application Service向Eureka Server有Get Registry的请求:

image.png

参考文章

实战内容

  • 本文是一篇实战的文章,实战内容如下:
    1. 启动Eureka server;
    2. 开发一个应用springcloudcustomizelistener,启动后会注册到Eureka server;
    3. 此时该应用身份为Eureka client,会周期性的从Eureka server获取服务列表(已有逻辑);
    4. 每次成功获取的服务列表成功都会存入本地缓存(已有逻辑);
    5. 存入缓存后,会在spring容器内发送广播(已有逻辑);
    6. 本次实战的重点就是自定义一个监听器来接收上述广播,收到广播后把详情用日志打印出来;
    7. 再启动另一个应用springclouddeepprovider,也会注册到Eureka server;
    8. 再去观察springcloudcustomizelistener的广播监听日志,会发现springclouddeepprovider的注册信息;

Eureka client缓存服务列表的源码简介

  • 实战前,先对Eureka client缓存服务列表的实现源码做个简介,这样才能做出匹配的监听器;

  • 应用作为Eureka Client的启动时,在com.netflix.discovery.DiscoveryClient类的initScheduledTasks方法中,会启动周期性任务,每隔30秒从Eureka server获取服务列表信息,如下图,红框中的TimedSupervisorTask负责周期性执行,绿框中的CacheRefreshThread负责具体的更新逻辑:

image.png

  • 在CacheRefreshThread类中经过层层调用,获取服务列表并更新本地缓存的逻辑在fetchRegistry方法中实现,如下图,红框中的getAndStoreFullRegistry方法负责全量更新,绿框中的getAndUpdateDelta方法负责增量更新,黄框中的onCacheRefreshed方法就是今天的重点:发送广播,广播类型是服务列表的本地缓存已更新

image.png

  • onCacheRefreshed方法在子类CloudEurekaClient中被重写,可见这里发送了一个普通的spring容器内广播,类型是HeartbeatEvent,我们可以自定义监听类来接收广播,并通过泛型规定只接受HeartbeatEvent类型:
    @Override
    protected void onCacheRefreshed() {
        if (this.cacheRefreshedCount != null) { //might be called during construction and will be null
            long newCount = this.cacheRefreshedCount.incrementAndGet();
            log.trace("onCacheRefreshed called with count: " + newCount);
            //spring容器内广播,HeartbeatEvent实例在创建时收到两个参数:CloudEurekaClient实例和缓存刷新次数
            this.publisher.publishEvent(new HeartbeatEvent(this, newCount));
        }
    }

实战应用设定

  • 本次实战要搭建一个小的Spring Cloud环境,包括以下应用:
应用名称 身份 作用 端口 启动顺序
springclouddeepeureka Eureka server 注册中心 8081 第一
springcloudcustomizelistener Eureka client 有自定义广播监听器,监听服务列表缓存更新的广播 8085 第二
springclouddeepprovider Eureka client 普通web应用 8082 第三

源码下载

  • springclouddeepeureka和springclouddeepprovider这两个应用,在文章《Spring Cloud源码分析之Eureka篇第一章:准备工作》中已有详细介绍,本文中就不多说了,您可以参考文章,也可以在github下载这两个应用的源码,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,本章源码分别在springclouddeepeureka、springclouddeepprovider这两个文件夹下,如下图红框所示:

image.png

启动springclouddeepeureka

  • 应用springclouddeepeureka开发完成后就立即启动,在浏览器访问地址:http://localhost:8081,可见Eureka server已经启动,不过还没有任何应用注册上来,如下图:

image.png

开发springcloudcustomizelistener

  • 接下来一起开发应用springcloudcustomizelistener,在此应用中添加自定义的spring广播监听器,如果您不想敲代码,也可以从github上直接下载源码,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springcloudcustomizelistener文件夹下,如下图红框所示:

image.png

  • 一起来开发吧:

  • 创建一个springboot的web应用,pom.xml内容如下,注意为了在日志中展示更详细的内容,依赖了fastjson库:
<?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>com.bolingcavalry</groupId>
    <artifactId>springcloudcustomizelistener</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>

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

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>1.5.9.RELEASE</version>
    </parent>

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

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

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

        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>fastjson</artifactId>
            <version>1.2.28</version>
        </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>Edgware.RELEASE</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>
</project>
  • 应用配置文件application.yml的内容如下:
server:
  port: 8085
spring:
  application:
    name: springcloud-customize-listener
eureka:
  client:
    serviceUrl:
      defaultZone: http://localhost:8081/eureka/
  instance:
    prefer-ip-address: true
  • 创建监听器EurekaCacheRefreshListener.java,前面已经分析过HeartbeatEvent实例的两个成员变量,值为缓存刷新次数和CloudEurekaClient实例,在收到广播时,将这两个成员变量都在日志中打印出来:
@Component
public class EurekaCacheRefreshListener implements ApplicationListener<HeartbeatEvent> {

    private static final Logger logger = LoggerFactory.getLogger(EurekaCacheRefreshListener.class);

    @Override
    public void onApplicationEvent(HeartbeatEvent event) {
        Object count = event.getValue();
        Object source = event.getSource();

        logger.info("start onApplicationEvent, count [{}], source :\n{}", count, JSON.toJSON(source));
    }
}
  • 启动应用,等待大约30秒左右,EurekaCacheRefreshListener中的日志就会在控制台输出,内容十分丰富,建议您复制这些内容去在线格式化JSON的网站做一下格式化再来看,下面列出部分关键信息,其他的内容已经略去:
{
    "instanceRemoteStatus": "UP",
    "lastSuccessfulHeartbeatTimePeriod": 316,
    "allKnownRegions": [
        "us-east-1"
    ],
    ...
    此处省略部分内容
    ...
    "applications": {
        "appsHashCode": "UP_1_",
        "registeredApplications": [
            {
                "instances": [
                    {
                        "hostName": "192.168.31.104",
                        "overriddenStatus": "UNKNOWN",
                        "metadata": {
                            "jmx.port": "64656",
                            "management.port": "8085"
                        },
                        "statusPageUrl": "http://192.168.31.104:8085/info",
                        "secureVipAddress": "springcloud-customize-listener",
                        "leaseInfo": {
                            "renewalIntervalInSecs": 30,
                            "registrationTimestamp": 1537827838033,
                            "evictionTimestamp": 0,
                            "renewalTimestamp": 1537827987419,
                            "durationInSecs": 90,
                            "serviceUpTimestamp": 1537827837461
                        },
                        "homePageUrl": "http://192.168.31.104:8085/",
                        "countryId": 1,
                        "sID": "na",
                        "securePort": 443,
                        "dataCenterInfo": {
                            "name": "MyOwn"
                        },
                        "instanceId": "DESKTOP-82CCEBN:springcloud-customize-listener:8085",
                        "coordinatingDiscoveryServer": false,
                        "id": "DESKTOP-82CCEBN:springcloud-customize-listener:8085",
                        "vIPAddress": "springcloud-customize-listener",
                        "dirty": false,
                        "lastUpdatedTimestamp": 1537827838033,
                        "healthCheckUrl": "http://192.168.31.104:8085/health",
                        "appName": "SPRINGCLOUD-CUSTOMIZE-LISTENER",
                        "lastDirtyTimestamp": 1537827837401,
                        "iPAddr": "192.168.31.104",
                        "version": "unknown",
                        "actionType": "ADDED",
                        "port": 8085,
                        "healthCheckUrls": [
                            "http://192.168.31.104:8085/health"
                        ],
                        "status": "UP"
                    }
                ]
  • 如上所示,当前应用的实例信息在本地已经缓存了;

启动springclouddeepprovider

  • 应用springclouddeepprovider是最后一个启动的应用,启动该应用后,再去观察springcloudcustomizelistener的日志,发现应用springclouddeepprovider的注册信息已经获取到了:
{
                "instances": [
                    {
                        "hostName": "192.168.119.1",
                        "overriddenStatus": "UNKNOWN",
                        "metadata": {
                            "jmx.port": "58420",
                            "management.port": "8082"
                        },
                        "statusPageUrl": "http://192.168.119.1:8082/info",
                        "secureVipAddress": "springcloud-deep-provider",
                        "leaseInfo": {
                            "renewalIntervalInSecs": 30,
                            "registrationTimestamp": 1537840715486,
                            "evictionTimestamp": 0,
                            "renewalTimestamp": 1537840715486,
                            "durationInSecs": 90,
                            "serviceUpTimestamp": 1537840715486
                        },
                        "homePageUrl": "http://192.168.119.1:8082/",
                        "countryId": 1,
                        "sID": "na",
                        "securePort": 443,
                        "dataCenterInfo": {
                            "name": "MyOwn"
                        },
                        "instanceId": "localhost:springcloud-deep-provider:8082",
                        "coordinatingDiscoveryServer": false,
                        "id": "localhost:springcloud-deep-provider:8082",
                        "vIPAddress": "springcloud-deep-provider",
                        "dirty": false,
                        "lastUpdatedTimestamp": 1537840715486,
                        "healthCheckUrl": "http://192.168.119.1:8082/health",
                        "appName": "SPRINGCLOUD-DEEP-PROVIDER",
                        "lastDirtyTimestamp": 1537840715451,
                        "iPAddr": "192.168.119.1",
                        "version": "unknown",
                        "actionType": "ADDED",
                        "port": 8082,
                        "healthCheckUrls": [
                            "http://192.168.119.1:8082/health"
                        ],
                        "status": "UP"
                    }
                ],
                "name": "SPRINGCLOUD-DEEP-PROVIDER",
                "instancesAsIsFromEureka": [
                    {
                        "hostName": "192.168.119.1",
                        "overriddenStatus": "UNKNOWN",
                        "metadata": {
                            "jmx.port": "58420",
                            "management.port": "8082"
                        },
                        "statusPageUrl": "http://192.168.119.1:8082/info",
                        "secureVipAddress": "springcloud-deep-provider",
                        "leaseInfo": {
                            "renewalIntervalInSecs": 30,
                            "registrationTimestamp": 1537840715486,
                            "evictionTimestamp": 0,
                            "renewalTimestamp": 1537840715486,
                            "durationInSecs": 90,
                            "serviceUpTimestamp": 1537840715486
                        },
                        "homePageUrl": "http://192.168.119.1:8082/",
                        "countryId": 1,
                        "sID": "na",
                        "securePort": 443,
                        "dataCenterInfo": {
                            "name": "MyOwn"
                        },
                        "instanceId": "localhost:springcloud-deep-provider:8082",
                        "coordinatingDiscoveryServer": false,
                        "id": "localhost:springcloud-deep-provider:8082",
                        "vIPAddress": "springcloud-deep-provider",
                        "dirty": false,
                        "lastUpdatedTimestamp": 1537840715486,
                        "healthCheckUrl": "http://192.168.119.1:8082/health",
                        "appName": "SPRINGCLOUD-DEEP-PROVIDER",
                        "lastDirtyTimestamp": 1537840715451,
                        "iPAddr": "192.168.119.1",
                        "version": "unknown",
                        "actionType": "ADDED",
                        "port": 8082,
                        "healthCheckUrls": [
                            "http://192.168.119.1:8082/health"
                        ],
                        "status": "UP"
                    }
                ]
            }
  • 至此,本次实战就完成了,通过开发自定义的广播监听器,我们对Eureka的注册发现机制有了进一步了解,在您的Spring Cloud学习过程中,希望本文能祝您一臂之力;

欢迎关注51CTO博客:程序员欣宸

学习路上,你不孤单,欣宸原创一路相伴...