eureka 注册Instances currently registered with Eureka 无实例

1、Eureka 简介

Eureka是Spring Cloud Netflix微服务套件中的一部分，可以与Springboot构建的微服务很容易的整合起来。
Eureka包含了服务器端和客户端组件。服务器端，也被称作是服务注册中心，用于提供服务的注册与发现。Eureka支持高可用的配置，当集群中有分片出现故障时，Eureka就会转入自动保护模式，它允许分片故障期间继续提供服务的发现和注册，当故障分片恢复正常时，集群中其他分片会把他们的状态再次同步回来。
客户端组件包含服务消费者与服务生产者。在应用程序运行时，Eureka客户端向注册中心注册自身提供的服务并周期性的发送心跳来更新它的服务租约。同时也可以从服务端查询当前注册的服务信息并把他们缓存到本地并周期性的刷新服务状态。

2、Eureka 未来（2.0版本不再进行开源工作）

如果开发者继续使用作为 2.x 分支上现有工作 repo 一部分发布的代码库和工件，则将自负风险，对此，专家建议开发者尽快将相关业务迁移到 Consul/ZooKeeper/Etcd 等工具上。

目前还未见 Netflix 官方对此作出进一步说明

3、担忧 Eureka 的未来，写个Demo缅怀一下吧。

3.1 搭建服务父类工程 module-parent

module-parent pom.xml

<?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.logan.springcloud</groupId>
    <artifactId>module-parent</artifactId>
    <version>0.1.0</version>
    <packaging>pom</packaging>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>1.5.15.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>

    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>Edgware.SR4</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>

    <repositories>
        <repository>
            <id>spring-milestones</id>
            <name>Spring Milestones</name>
            <url>https://repo.spring.io/milestone</url>
            <snapshots>
                <enabled>false</enabled>
            </snapshots>
        </repository>
        <repository>
            <id>maven-ali</id>
            <url>http://maven.aliyun.com/nexus/content/groups/public//</url>
            <releases>
                <enabled>true</enabled>
            </releases>
            <snapshots>
                <enabled>true</enabled>
                <updatePolicy>always</updatePolicy>
                <checksumPolicy>fail</checksumPolicy>
            </snapshots>
        </repository>
    </repositories>

</project>

3.2 搭建服务注册中心 module-eureka

module-eureka pom.xml

<?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>

    <artifactId>module-eureka</artifactId>
    <packaging>jar</packaging>

    <parent>
        <artifactId>module-parent</artifactId>
        <groupId>com.logan.springcloud</groupId>
        <version>0.1.0</version>
    </parent>

    <dependencies>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-netflix-eureka-server</artifactId>
        </dependency>
    </dependencies>

</project>

module-eureka 启动类 EurekaServerStarter.java

package com.logan.springcloud;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.eureka.server.EnableEurekaServer;

/**
 * 服务注册中心Server
 * Created by Logan on 2018/8/26.
 */
@SpringBootApplication
@EnableEurekaServer
public class EurekaServerStarter {

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

}

module-eureka 配置文件 application.yml

spring:
  application:
    name: module-eureka
server:
  port: 8761

eureka:
  instance:
    hostname: localhost
  client:
    #由于该应用为注册中心,所以设置为false,代表不向注册中心注册自己
    registerWithEureka: false
    #由于注册中心的职责就是维护服务实例,它并不需要去检索服务,所以也设置为false
    fetchRegistry: false
    service-url:
      defaultZone: http://localhost:8761/eureka/
  server:
      enable-self-preservation: false

4、搭建服务提供者 module-service-producer

pom.xml

<?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>
		<artifactId>module-parent</artifactId>
		<groupId>com.logan.springcloud</groupId>
		<version>0.1.0</version>
	</parent>

	<groupId>com.logan.springcloud</groupId>
	<artifactId>module-service-producer</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<packaging>jar</packaging>

	<name>module-service-producer</name>
	<description>Demo project for Spring Boot</description>


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

		<dependency>
			<groupId>com.h2database</groupId>
			<artifactId>h2</artifactId>
			<scope>runtime</scope>
		</dependency>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-test</artifactId>
			<scope>test</scope>
		</dependency>
		<dependency>
			<groupId>org.springframework.cloud</groupId>
			<artifactId>spring-cloud-starter-eureka</artifactId>
		</dependency>
	</dependencies>

	<build>
		<plugins>
			<plugin>
				<groupId>org.springframework.boot</groupId>
				<artifactId>spring-boot-maven-plugin</artifactId>
			</plugin>
		</plugins>
	</build>

</project>

application.yml

server:
  port: 7900
spring:
  application:
    name: module-service-provider
  jpa:
    generate-ddl: false
    show-sql: true
    hibernate:
      ddl-auto: none
  datasource:
    platform: h2
    schema: classpath:schema.sql
    data: classpath:data.sql
logging:
  level:
    root: INFO
    org.hibernate: INFO
    org.hibernate.type.descriptor.sql.BasicBinder: TRACE
    org.hibernate.type.descriptor.sql.BasicExtractor: TRACE
    com.itmuch: DEBUG

# Eureka 服务提供者配置
eureka:
  client:
    service-url:
      #注册中心的地址
      defaultZone: http://localhost:8761/eureka/
  instance:
      instance-id: module-service-provider
      #访问路径可以显示IP地址
      prefer-ip-address: true

启动类 ProducerApplicationStarter.java

package com.logan.springcloud;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.eureka.EnableEurekaClient;

@SpringBootApplication
@EnableEurekaClient
public class ProducerApplicationStarter {

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

5.0 启动EurekaServer 和 Eureka 服务提供者

 

大家注意到红色部分的字体，笔者为了开发调试方便，关闭了Eureka的自我保护机制（服务不可用，Eureka不会删除已注册服务）

点击服务名称，在url上调用poducer的rest服务，调用成功。

 

 

完整代码见 Github。

https://github.com/JasonBabylon/spring-cloud-eureka