概要
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
什么是Spring Cloud Eureka?
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.
使用Eureka获取服务调用
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)
<parent>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-parent</artifactId>
<version>Brixton.SR4</version>
<relativePath/>
</parent>
<dependencies>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-eureka-server</artifactId>
</dependency>
</dependencies>配置应用信息-端口和应用名称 application.yml
server:
port: 8010
spring:
application:
name: mmb-eureka-server启动服务
@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)
<parent>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-parent</artifactId>
<version>Brixton.SR4</version>
<relativePath/>
</parent>
<dependencies>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-eureka</artifactId>
</dependency>
</dependencies>
配置应用信息-eureka server信息,实际使用的words信息,端口号 (application.yml)
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)
spring:
application:
name: mmb-eureka-client-subject添加Controller-随机获取words中的一条
@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
@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)
<parent>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-parent</artifactId>
<version>Brixton.SR4</version>
<relativePath/>
</parent>
<dependencies>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-eureka</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-actuator</artifactId>
</dependency>
</dependencies>配置应用信息-eureka server和端口号 (application.yml)
eureka:
client:
serviceUrl:
defaultZone: http://localhost:8010/eureka/
server:
port: 8020配置启动信息-应用名称 (bootstrap.yml)
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
@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<ServiceInstance> 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
@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
Eureka整合Spring Config Server
在git的repository里添加application.yml
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.
---
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 构建Eureka Server集群
host文件中添加 (c:WINDOWSsystem32driversetchosts).
127.0.0.1 eureka-primary
127.0.0.1 eureka-secondary
127.0.0.1 eureka-tertiaryEureka Server的application.yml添加多个profiles,和instanceId
---
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
---
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
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
java
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