spring cloud 实现Eureka注册服务

服务注册和发现

原文网址：https://spring.io/guides/gs/service-registration-and-discovery/

What you'll build

你将配置一个Eureka service注册中心和一个client，client能自动注册到注册中心来解决端口问题。一个服务注册中心非常有用，它使得client-side负载均衡，并从 consumers分离服务的providers而不需要DNS。

What you'll need

15分钟

一个自己喜欢的编辑器或IDE

JDK1.8以上

Gradle 2.3+ 或者 Maven 3.0+

How to complete this guide

获取源码

git clone https://github.com/spring-guides/gs-service-registration-and-discovery.git
build with Gradle

创建gradle工程，设置build.gradle

eureka-service/build.gradle

buildscript {ext {springBootVersion = '1.5.2.RELEASE'}repositories {mavenCentral()}dependencies {classpath("org.springframework.boot:spring-boot-gradle-plugin:${springBootVersion}")}}apply plugin: 'java'apply plugin: 'eclipse'apply plugin: 'idea'apply plugin: 'org.springframework.boot'jar {baseName = 'eureka-service'version = '0.0.1-SNAPSHOT'}sourceCompatibility = 1.8targetCompatibility = 1.8repositories {mavenCentral()}dependencyManagement {imports {mavenBom 'org.springframework.cloud:spring-cloud-dependencies:Camden.SR5'}}dependencies {compile('org.springframework.cloud:spring-cloud-starter-eureka-server')testCompile('org.springframework.boot:spring-boot-starter-test')}eclipse {classpath { containers.remove('org.eclipse.jdt.launching.JRE_CONTAINER') containers 'org.eclipse.jdt.launching.JRE_CONTAINER/org.eclipse.jdt.internal.debug.ui.launcher.StandardVMType/JavaSE-1.8'}}

eureka-client/build.gradle

buildscript {ext {springBootVersion = '1.5.2.RELEASE'}repositories {mavenCentral()}dependencies {classpath("org.springframework.boot:spring-boot-gradle-plugin:${springBootVersion}")}}apply plugin: 'java'apply plugin: 'eclipse'apply plugin: 'idea'apply plugin: 'org.springframework.boot'jar {baseName = 'eureka-client'version = '0.0.1-SNAPSHOT'}sourceCompatibility = 1.8targetCompatibility = 1.8repositories {mavenCentral()}dependencyManagement {imports {mavenBom 'org.springframework.cloud:spring-cloud-dependencies:Camden.SR5'}}dependencies {compile('org.springframework.cloud:spring-cloud-starter-eureka')compile('org.springframework.boot:spring-boot-starter-web')testCompile('org.springframework.boot:spring-boot-starter-test')testCompile('org.springframework.cloud:spring-cloud-starter-eureka-server')}eclipse {classpath { containers.remove('org.eclipse.jdt.launching.JRE_CONTAINER') containers 'org.eclipse.jdt.launching.JRE_CONTAINER/org.eclipse.jdt.internal.debug.ui.launcher.StandardVMType/JavaSE-1.8'}}

Spring Boot Gradle Plugin提供了许多便利的特性：

• 它收集classpath中所有的jar包，并build一个独立的，可运行的“uber-jar”，使得执行和传递服务更为方便
• 它寻找public static void main()方法来标记可执行的类
• 它提供一个嵌入的依赖解析器，设置版本号匹配Spring Boot依赖。你可以重写成任意版本，但是他将默认为Boot的选择版本集。

build with Maven

 创建Maven工程

eureka-server/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.example</groupId><artifactId>eureka-service</artifactId><version>0.0.1-SNAPSHOT</version><packaging>jar</packaging><parent><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-parent</artifactId><version>1.5.2.RELEASE</version><relativePath/> <!-- lookup parent from repository --></parent><properties><project.build.sourceEncoding>UTF-8</project.build.sourceEncoding><java.version>1.8</java.version></properties><dependencies><dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-starter-eureka-server</artifactId></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-test</artifactId><scope>test</scope></dependency></dependencies><dependencyManagement><dependencies><dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-dependencies</artifactId><version>Camden.SR5</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>

eureka-client/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.example</groupId><artifactId>eureka-client</artifactId><version>0.0.1-SNAPSHOT</version><packaging>jar</packaging><parent><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-parent</artifactId><version>1.5.2.RELEASE</version><relativePath/> <!-- lookup parent from repository --></parent><properties><project.build.sourceEncoding>UTF-8</project.build.sourceEncoding><java.version>1.8</java.version></properties><dependencies><dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-starter-eureka</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-eureka-server</artifactId><scope>test</scope></dependency></dependencies><dependencyManagement><dependencies><dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-dependencies</artifactId><version>Camden.SR5</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>

Spring Boot Maven plugin提高了许多方便的特性： 同上 gradle plugin

build with your IDE
Stand up a Eureka Service Registry

你首先需要一个Eureka Service注册中心，你可以使用Spring Cloud的@EnableEurekaServer来建立注册中心，以便其他应用访问。这是一个普通的Spring Boot应用，加上注解来提供服务注册功能。

service中创建一个application.java

package hello;import org.springframework.boot.SpringApplication;import org.springframework.boot.autoconfigure.SpringBootApplication;import org.springframework.cloud.netflix.eureka.server.EnableEurekaServer;@EnableEurekaServer@SpringBootApplicationpublic class EurekaServiceApplication {    public static void main(String[] args) {        SpringApplication.run(EurekaServiceApplication.class, args);    }}

当注册中心启动时，会发生错误，带有堆栈信息：“没有注册中心可连接的副本节点”。在生产环境下，你想要注册中心不止一个实例，然而，出于简单的目的，它足以使相关日志失效。

默认情况下，注册中心也将试图将自己也注册上，所以你也需要禁止它注册。

一般在本地使用时，协定将注册中心放在一个单独的端口上。

添加一些属性来处理这些要求：

配置文件eureka-service/src/main/resources/application.properties

server.port=8761eureka.client.register-with-eureka=falseeureka.client.fetch-registry=falselogging.level.com.netflix.eureka=OFFlogging.level.com.netflix.discovery=OFF

Talking to the Registry

现在我们已经搭建好注册中心了，现在搭建一个客户端，让它在注册中心自己注册，并且使用Spring Cloud DiscoveryClient抽象去注册中心询问主机和端口。@EnableDiscoveryClient 激活Netflix Eureka DiscoveryClient实现。还有其他实现用于其他服务注册中心，如 Hashicorp’s Consul or Apache Zookeeper.

client中创建application.java

package hello;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.boot.SpringApplication;import org.springframework.boot.autoconfigure.SpringBootApplication;import org.springframework.cloud.client.ServiceInstance;import org.springframework.cloud.client.discovery.DiscoveryClient;import org.springframework.cloud.client.discovery.EnableDiscoveryClient;import org.springframework.web.bind.annotation.PathVariable;import org.springframework.web.bind.annotation.RequestMapping;import org.springframework.web.bind.annotation.RestController;import java.util.List;@EnableDiscoveryClient@SpringBootApplicationpublic class EurekaClientApplication {    public static void main(String[] args) {        SpringApplication.run(EurekaClientApplication.class, args);    }}@RestControllerclass ServiceInstanceRestController {    @Autowired    private DiscoveryClient discoveryClient;    @RequestMapping("/service-instances/{applicationName}")    public List<ServiceInstance> serviceInstancesByApplicationName(            @PathVariable String applicationName) {        return this.discoveryClient.getInstances(applicationName);    }}

无论你选择哪种实现，你将发现eureka-client注册在了你在spring.application.name定义的属性名下。这个属性在Spring Cloud中用的很多，通常在服务配置的最初阶段，此属性用在service bootstrap，所以为了方便，将它放在： eureka-client/src/main/resources/bootstrap.properties此文件将先于src/main/resources/application.properties被发现

eureka-client/src/main/resources/bootstrap.properties

spring.application.name=a-bootiful-client

eureka-client定义一个Spring MVC REST端点，ServiceInstanceRestController，它将返回一个枚举，其中包含了注册中心在http://localhost:8080/service-instances/a-bootiful-client注册的所有ServiceInstance实例。查阅 Building a RESTful Web Service指导来学习更多关于用Spring MVC 和 Spring Boot建立REST服务。

Test the application

测试end-to-end(端对端)结果，首先启动eureka-service，加载完毕后，启动eureka-client，客户端将花一分钟将它注册到注册中心，并从注册中心刷新它自己已注册是实例列表。所有的这些阈值都是可配置的，在浏览器中访问客户端http://localhost:8080/service-instances/a-bootiful-client。你将看到客户端的ServiceInstance 映射在响应中。

遇到的问题：

1. 客户端注册不成功，找不到server，解决办法：在bootstrap.properties中配置server地址：eureka.client.serviceUrl.defaultZone=http://localhost:8761/eureka/