Spring Cloud实战(二)-Spring Cloud Eureka

摘要：概要什么是使用获取服务调用整合构建集群什么是模块提供的功能是被动式的服务发现什么是服务发现服务发现就像聊天室一个每个用户来的时候去服务器上注册这样他的好友们就能看到你你同时也将获取好友的上线列表在微服务中服务就相当于聊天室的用户而服务注册中

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什么是Spring Cloud Eureka?
使用Eureka获取服务调用
Eureka整合Spring Config Server
构建Eureka Server集群

Spring Cloud Eureka 模块提供的功能是被动式的服务发现.
什么是服务发现?
服务发现就像聊天室一个,每个用户来的时候去服务器上注册,这样他的好友们就能看到你,你同时也将获取好友的上线列表.
在微服务中,服务就相当于聊天室的用户,而服务注册中心就像聊天室服务器一样,目前服务发现的解决方案有Eureka,Consul,Etcd,Zookeeper,SmartStack,等等.

本文就来讲讲Eureka,如图所示,Eureka Client通过HTTP(或者TCP,UDP)去Eureka Server注册和获取服务列表,为了高可用一般会有多个Eureka Server组成集群.Eureka会移除那些心跳检查未到达的服务.

这节我们将构建一个Eureka Server,5个Eureka Client(分别提供主语,动词,量词,形容词,名词服务),再构建一个Sentence Eureka Client 来用前面五个服务造句.

1.创建mmb-eureka-server

添加依赖-spring-cloud-starter-parent,spring-cloud-starter-eureka-server(pom.xml)

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        org.springframework.cloud
        spring-cloud-starter-parent
        Brixton.SR4
        
    
    
        
            org.springframework.cloud
            spring-cloud-starter-eureka-server
        
    

配置应用信息-端口和应用名称 application.yml

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server:
  port: 8010
spring:
  application:
    name: mmb-eureka-server

启动服务

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

打开管理页面,检查是否成功

2.创建mmb-eureka-client

添加依赖-spring-cloud-starter-parent,spring-cloud-starter-eureka (pom.xml)

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        org.springframework.cloud
        spring-cloud-starter-parent
        Brixton.SR4
        
    
    
        
            org.springframework.cloud
            spring-cloud-starter-eureka
        
    

配置应用信息-eureka server信息,实际使用的words信息,端口号 (application.yml)

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eureka:
  client:
    service-url:
      defaultZone: http://localhost:8010/eureka/
words: 你,我,他
server:
  port: ${PORT:${SERVER_PORT:0}}
#  这个的意思是随机指定个没使用的端口

配置启动信息-应用名称 (bootstrap.xml)

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spring:
  application:
    name: mmb-eureka-client-subject

添加Controller-随机获取words中的一条

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@RestController
public class Controller {
   @Value("${words}") String words;
    @RequestMapping("/")
    public  String getWord() {
        String[] wordArray = words.split(",");
        int i = (int)Math.round(Math.random() * (wordArray.length - 1));
        return wordArray[i];
    }
}

启动服务

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

访问127.0.0.1/port(看日志可以得到各个应用的port) 看到words里的词就启动成功了,

其它的verb,acticle,adjective,noun工程类似,就把words,和spring.application.name改成对应的工程名字就好了

3.创建sentence工程

添加依赖-spring-cloud-starter-parent,spring-cloud-starter-eureka,spring-boot-starter-web,spring-boot-starter-actuator (pom.xml)

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        org.springframework.cloud
        spring-cloud-starter-parent
        Brixton.SR4
        
    
    
        
            org.springframework.cloud
            spring-cloud-starter-eureka
        
        
            org.springframework.boot
            spring-boot-starter-web
        
        
            org.springframework.boot
            spring-boot-starter-actuator
        
    

配置应用信息-eureka server和端口号 (application.yml)

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eureka:
  client:
    serviceUrl:
      defaultZone: http://localhost:8010/eureka/
server:
  port: 8020

配置启动信息-应用名称 (bootstrap.yml)

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spring:
  application:
    name: mmb-eureka-sentence

添加Controller-用其他eureka-clients(subject,verb,acticle,adjective,noun)的各个服务造句

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@RestController
public class Controller {
    @Autowired
    DiscoveryClient client;
    @RequestMapping("/sentence")
    public  String getSentence() {
        return
                getWord("mmb-eureka-client-subject") + " "
                        + getWord("MMB-EUREKA-CLIENT-VERB") + " "
                        + getWord("mmb-eureka-client-article") + " "
                        + getWord("mmb-eureka-client-adjective") + " "
                        + getWord("mmb-eureka-client-noun") + "."
                ;//大小写不区分
    }
    public String getWord(String service) {
        List list = client.getInstances(service);
        if (list != null && list.size() > 0 ) {
            URI uri = list.get(0).getUri();
            if (uri !=null ) {
                return (new RestTemplate()).getForObject(uri,String.class);
            }
        }
        return null;
    }
}

启动服务

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

先启动Eureka Server,再启动Eureka Client,在管理页面上看到服务都起成功时,访问127.0.0.1/8020/sentence 可以得到一个随机组成的句子

在git的repository里添加application.yml

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 eureka:
  client:
    serviceUrl:
      defaultZone: http://localhost:8010/eureka/

启动实战(一)中的Spring Cloud Config Server

修改各个client的配置

application.yml移除属性eureka.client.serviceUrl.defaultZone

bootstrap.yml添加属性 spring.cloud.config.uri: http://localhost:8001

pom.xml添加依赖spring-cloud-config-client

依次启动Config Server,Eureka Server,Eureka Client,在管理页面上看到服务都起成功时,访问127.0.0.1/8020/sentence 可以得到一个随机组成的句子
-

如果你想把words信息也放入repository呢?在application.yml中添加,如下信息,各个client启动的时候加上-Dspring.profiles.active对应到相应的启动参数就行了.

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    ---
  spring:
    profiles: subject
  words: I,You,He,She,It
  
  ---
  spring:
    profiles: verb
  words: ran,knew,had,saw,bought
  ---
  spring:
    profiles: article
  words: a,the
  ---
  spring:
    profiles: adjective
  words: reasonable,leaky,suspicious,ordinary,unlikely
  ---
  spring:
    profiles: noun
  words: boat,book,vote,seat,backpack,partition,groundhog  

host文件中添加 (c:WINDOWSsystem32driversetchosts).

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  127.0.0.1       eureka-primary
  127.0.0.1       eureka-secondary
  127.0.0.1       eureka-tertiary

Eureka Server的application.yml添加多个profiles,和instanceId

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 ---
spring:
  application:
    name: eureka-server-clustered   
  profiles: primary
server:
  port: 8011  
eureka:
  instance:
    hostname: eureka-primary       
  ---
spring:
  application:
    name: eureka-server-clustered      
  profiles: secondary
server:
  port: 8012
eureka:
  instance:
    hostname: eureka-secondary       
 ---
spring:
  application:
    name: eureka-server-clustered      
  profiles: tertiary
server:
  port: 8013
eureka:
  instance:
    hostname: eureka-tertiary       

此时Eureka Server 同时也是个Eureka Client,需要设置eureka.client.serviceUrl.defaultZone,值是另外两个,最终会是下面这样

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---
spring:
  application:
    name: eureka-server-clustered   
  profiles: primary
server:
  port: 8011  
eureka:
  instance:
    hostname: eureka-primary       
  client:
    registerWithEureka: true
    fetchRegistry: true        
    serviceUrl:
      defaultZone: http://eureka-secondary:8012/eureka/,http://eureka-tertiary:8013/eureka/
---
spring:
  application:
    name: eureka-server-clustered      
  profiles: secondary
server:
  port: 8012
eureka:
  instance:
    hostname: eureka-secondary       
  client:
    registerWithEureka: true
    fetchRegistry: true        
    serviceUrl:
      defaultZone: http://eureka-tertiary:8013/eureka/,http://eureka-primary:8011/eureka/
---
spring:
  application:
    name: eureka-server-clustered      
  profiles: tertiary
server:
  port: 8013
eureka:
  instance:
    hostname: eureka-tertiary       
  client:
    registerWithEureka: true
    fetchRegistry: true    
    serviceUrl:
      defaultZone: http://eureka-primary:8011/eureka/,http://eureka-secondary:8012/eureka/      

以-Dspring.profiles.active=primary (and secondary, and tertiary)为启动参数分别启动Eureka Server

修改所有Eureka Client的eureka.client.serviceUrl.defaultZone值为http://eureka-primary:8011/eu...逗号分隔,无空白),集群启动成功登录管理页面查看,如下图所示即成功

再启动所有的Eureka Clients,查看http://localhost:8020/sentence 是否成功

为了测试容错性,关掉两个Eureka Client,重启若干个Eureka Client,观察启动是否报错,再去查看查看http://localhost:8020/sentence 是否成功

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特别感谢 kennyk65
Spring Cloud 中文用户组 31777218
Spring-Cloud-Config  官方文档-中文译本 (本人有参与,哈哈)
Spring Cloud Netflix 官网文档-中文译本
本文实例github地址 mmb-eureka