SpringCloud 进阶之Eureka(服务注册和发现)

1. Eureka 服务注册与发现

• Eureka 是一个基于REST的服务,用于服务的的注册与发现;
• Eureka采用C-S的设计架构,Eureka Server作为服务注册功能的服务器,它是服务注册中心;
• Eureka包含两个组件:Eureka Server 和 Eureka Client
  • Eureka Server提供服务注册和发现;
  • Eureka Client是一个java客户端;

1.1 三大角色

• Eureka Server提供服务注册和发现;
• Service Provider服务提供方将自身服务注册到Eureka,从而使服务消费方能够找到;
• Service Consumer服务消费方从Eureka获取注册服务列表,从而能够消费服务;

1.2 Eureka 服务注册中心Module(microservicecloud-eureka-7001)

// pom.xml
<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>com.noodles.springcloud</groupId>
    <artifactId>microservicecloud</artifactId>
    <version>0.0.1-SNAPSHOT</version>
  </parent>

  <artifactId>microservicecloud-eureka-7001</artifactId>
  <dependencies>
  	  <!-- eureka-server 服务端 -->
  	  <dependency>
  	  	<groupId>org.springframework.cloud</groupId>
  	  	<artifactId>spring-cloud-starter-eureka-server</artifactId>
  	  </dependency>
	  <!-- 修改后立即生效,热部署 -->
	  	<dependency>
	  		<groupId>org.springframework</groupId>
	  		<artifactId>springloaded</artifactId>
	  	</dependency>
	  	<dependency>
	  		<groupId>org.springframework.boot</groupId>
	  		<artifactId>spring-boot-devtools</artifactId>
	  	</dependency>
  </dependencies>
</project>


// application.yml
server:
  port: 7001

eureka:
  instance:
    hostname: localhost  #eureka服务端的实例名称
  client:
    register-with-eureka: false # false 表示不向注册中心注册自己
    fetch-registry: false   # false 表示自己就是注册中心,职责是维护服务实例,并不需要检索服务
    service-url:
      defaultZone: http://${eureka.instance.hostname}:${server.port}/eureka
       #设置与Eureka Server交互的地址,查询和注册服务都需要依赖这个地址


// com.noodles.springcloud
// EurekaServer7001_App
@SpringBootApplication
@EnableEurekaServer  // EurekaServer 服务器端启动类,接收其他微服务注册进来
public class EurekaServer7001_App {

	public static void main(String[] args) {
		SpringApplication.run(EurekaServer7001_App.class, args);
	}
}


// 测试
// 访问: http://localhost:7001

1.3 将已有的部门微服务注册进eureka服务中心(microservicecloud-provider-dept-8001)

// 修改microservicecloud-provider-dept-8001
// pom.xml 增加
<!-- 将微服务provider 注册进 eureka -->
<dependency>
	<groupId>org.springframework.cloud</groupId>
	<artifactId>spring-cloud-starter-eureka</artifactId>
</dependency>
<dependency>
	<groupId>org.springframework.cloud</groupId>
	<artifactId>spring-cloud-starter-config</artifactId>
</dependency>


// application.yml 增加
eureka:
  client: # 客户端注册进eureka服务列表内
    service-url:
      defaultZone: http://localhost:7001/eureka


// DeptProvider8001_App 主启动类
@SpringBootApplication
@EnableEurekaClient	// 本服务启动后,自动注册进eureka服务中
public class DeptProvider8001_App {

	public static void main(String[] args) {
		SpringApplication.run(DeptProvider8001_App.class, args);
	}
}


// 测试
// 先要启动 EurekaServer,然后启动 DeptProvicer8001_App
// 访问:http://localhost:7001/

1.3.1 actuator 与注册微服务信息完善

• 主机映射名称修改
• 访问信息有IP信息提示
• 微服务info内容详细信息

修改之前

修改之后

// 主机映射名称修改
// 修改microservicecloud-provider-dept-8001
// application.xml
eureka:
  client: # 客户端注册进eureka服务列表内
    service-url:
      defaultZone: http://localhost:7001/eureka
  instance:
    instance-id: microservicecloud-dept8001     # 主机映射名称


// 访问信息有IP信息提示
// 修改microservicecloud-provider-dept-8001
// application.xml
eureka:
  client: # 客户端注册进eureka服务列表内
    service-url:
      defaultZone: http://localhost:7001/eureka
  instance:
    instance-id: microservicecloud-dept8001     # 主机映射名称
    prefer-ip-address: true                     # 访问路径可以显示IP地址


// 微服务info内容详细信息
// 修改microservicecloud-provider-dept-8001
// pom.xml
<!-- actutator 监控信息完善 -->

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

// 修改父工程 microservicecloud
// pom.xml
<!-- dependencyManagement  -->
<build>
  	<finalName>microservicecloud</finalName>
  	<resources>
  		<resource>
  			<directory>src/main/resources</directory>
  			<filtering>true</filtering>
  		</resource>
  	</resources>
  	<plugins>
  		<plugin>
  			<groupId>org.apache.maven.plugins</groupId>
  			<artifactId>maven-resources-plugin</artifactId>
            <version>2.6</version>
  			<configuration>
  				<delimiters>
  					<delimit>$</delimit>
  				</delimiters>
  			</configuration>
  		</plugin>
  	</plugins>
  </build>

<!-- modules -->

// 修改microservicecloud-provider-dept-8001
// application.yml
info:
  app.name: noodles-microservicecloud
  company.name: www.google.com
  build.artifactId: $project.artifactId$
  build.version: $project.version$

1.3.2 Eureka 自我保护机制

// 修改 microservicecloud-eureka-7001
// 将自我保护机制关闭(不推荐)
// application.yml
eureka:
  server:
    enable-self-preservation: false

1.3.3 Eureka 服务发现

// 修改 microservicecloud-provider-dept-8001
@RestController
public class DeptController {

	@Autowired
	private DeptService deptService;

	@Autowired
	private DiscoveryClient client;

	@RequestMapping(value = "/dept/discovery", method=RequestMethod.GET)
	public Object discovery() {
		List<String> list = client.getServices();
		System.out.println("==========="+list);

		List<ServiceInstance> srvList = client.getInstances("MICROSERVICECLOUD-DEPT");
		for(ServiceInstance element : srvList) {
			System.out.println(element.getServiceId()+"	"+element.getHost()+"	"+element.getPort()+
            "	"+element.getUri());
		}
		return this.client;
	}
}


// DeptProvider8001_App 主启动类
@SpringBootApplication
@EnableEurekaClient	// 本服务启动后,自动注册进eureka服务中
@EnableDiscoveryClient  // 服务发现
public class DeptProvider8001_App {

	public static void main(String[] args) {
		SpringApplication.run(DeptProvider8001_App.class, args);
	}
}


// 修改 microservicecloud-consumer-dept-80 工程的 DeptController Consumer
@RequestMapping(value="/consumer/dept/discovery")
public Object discovery() {
	return restTemplate.getForObject(REST_URL_PREFIX+"/dept/discovery", Object.class);
}

2. Eureka 集群

// 新建microservicecloud-eureka-7002/microservicecloud-eureka-7003

// 按照7001为模板粘贴POM

// 修改7002和7003的主启动类

// 修改映射配置 hosts
127.0.0.1 eureka7001.com
127.0.0.1 eureka7002.com
127.0.0.1 eureka7003.com

// 7001 application.yml
server:
  port: 7001

eureka:
  instance:
    hostname: eureka7001.com  #eureka服务端的实例名称
  client:
    register-with-eureka: false
    fetch-registry: false
    service-url:
       defaultZone: http://eureka7002.com:7002/eureka/,http://eureka7003.com:7003/eureka/

// 7002 application.yml
server:
  port: 7002

eureka:
  instance:
    hostname: eureka7002.com  #eureka服务端的实例名称
  client:
    register-with-eureka: false
    fetch-registry: false
    service-url:
       defaultZone: http://eureka7001.com:7001/eureka/,http://eureka7003.com:7003/eureka/


// microservicecloud-provider-dept-8001
// 微服务发布到3台eureka集群配置中, application.yml
eureka:
  client: # 客户端注册进eureka服务列表内
    service-url:
      defaultZone: http://eureka7001.com:7001/eureka,http://eureka7002.com:7002/eureka,http://eureka7003.com:7003/eureka

// 测试访问:
// http://eureka7001.com:7001
// http://eureka7002.com:7002
// http://eureka7003.com:7003

3. Eureka和Zookeeper比较

• Eureka遵守AP原则(可用性,分区容错性)
• Zookeeper遵守CP原则(强一致性,分区容错性)

参考资料:

• SpringCloud 进阶