构建服务注册中心

创建工程

  首先创建一个基本的SpringBoot工程，命名为eurekaserver，向pom文件中引入必要的依赖。

<?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.example</groupId>
    <artifactId>demo</artifactId>
    <version>1.0-SNAPSHOT</version>
    <packaging>jar</packaging>

    <name>eureka-server</name>
    <description>Demo project for Spring Boot</description>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.0.4.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </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.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>

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

    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>Finchley.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>

启动类EurekaServerApplication

在启动类上添加@EnableEurekaServer注解

package com.example.demo;

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

@SpringBootApplication
@EnableEurekaServer
public class EurekaServerApplication {

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

配置文件application.yaml

#不向服务中心注册自身
eureka.client.register-with-eureka=false
#不检索服务
eureka.client.fetch-registry=false

注册服务提供者

  使用上一章的工程，作为服务发布自己。首先在pom中加入eureka的依赖:

<dependencies>

        <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>
        <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-netflix-eureka-server</artifactId>
        </dependency>

    </dependencies>

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

  在主类中添加@EnableEurekaClient注解

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

@EnableEurekaClient
@SpringBootApplication
public class Application {

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

  最后，需要在application.properties文件中对服务命名，并配置之前构建的服务注册中心地址:

spring.application.name=hello-service
#多个地址用逗号分隔
eureka.client.service-url.defaultZone=http://localhost:8080/eureka

56B6935A-BE82-4A75-9049-5B5D7445C67E.png

高可用注册中心

  在生产环境中，我们会注册多个eureka注册中心实例来保证服务的高可用性。我们可以在之前的注册实例工程之上进行扩展，创建application-dev.properties和application-test.properties文件,并在hosts文件中修改dev、test使其指向127.0.0.1。

spring.application.name=eureka-server
server.port=2222
eureka.instance.hostname=dev
eureka.client.service-url.defaultZone=http://test:1111/eureka
eureka.client.register-with-eureka=true 
eureka.client.fetch-registry=true

spring.application.name=eureka-server
server.port=1111
eureka.instance.hostname=test
eureka.client.service-url.defaultZone=http://dev:2222/eureka
eureka.client.register-with-eureka=true 
eureka.client.fetch-registry=true

  使用两个配置文件分别启动注册中心之后，需要对之前的hello-service配置文件进行修改:

eureka.client.service-url.defaultZone=http://localhost:1111/eureka,http://localhost:2222/eureka

eureka集群available-replicas不为空需满足如下条件：
  1.不能用localhost比如：
  eureka.client.service-url.defaultZone=http://localhost:2222/eureka
  要采用：
  eureka.client.serviceUrl.defaultZone=http://dev:2222/eureka
  2.相互注册要开启：
  eureka.client.register-with-eureka=true
  eureka.client.fetch-registry=true