Eureka学习

Eureka学习

介绍

Eureka 是一款开源的服务注册与发现组件，通过配合其他组件可提供负载均衡能力

名称	类型	AP/CP	语言	依赖	集成	一致性算法
Eureka	General	AP	java	jvm	Java Client
Zookeeper	General	CP	java		Client Bingding	paxos
cnosul	General	CP	go	jvm	HTTP/DNS library	Raft

CAP理论：

C（Consistency）：数据一致性，当存在多个副本的情况下， 由于网络，机器故障，程序内部错误等原因出现数据写入副本成功部分，这种情况下会出现数据的不一致，一致性的要求是在对数据的更新完成后，多个副本的数据是一一致的

A（Availability）：客户端在对集群进行读写的时候，能够正常请求，但是数据的更新最终结果会有延迟，即在一定的时间内完成，也就是最终一致性

P（Partition Tolerrance）：分区容忍性，即发生通信故障时，一个集群本分为多个无法互相通信的分区时，集群仍然可用

创建Eureka Server

1. 在POM.xml增加依赖：spring-cloud-starter-netflix-eureka-server

   <?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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
       <modelVersion>4.0.0</modelVersion>
       <parent>
           <groupId>org.springframework.boot</groupId>
           <artifactId>spring-boot-starter-parent</artifactId>
           <version>2.3.5.RELEASE</version>
           <relativePath/> <!-- lookup parent from repository -->
       </parent>
       <groupId>com.example</groupId>
       <artifactId>demo</artifactId>
       <version>0.0.1-SNAPSHOT</version>
       <name>spring-boot2</name>
       <description>Demo project for Spring Boot</description>
   ​
       <properties>
           <java.version>8</java.version>
           <spring-cloud.version>Finchley.RELEASE</spring-cloud.version>
       </properties>
       
   ​
       <dependencies>
           <dependency>
               <groupId>org.springframework.boot</groupId>
               <artifactId>spring-boot-starter-web</artifactId>
           </dependency>
           <dependency>
               <groupId>org.springframework.cloud</groupId>
               <artifactId>spring-cloud-starter-netflix-eureka-server</artifactId>
               <version>2.2.3.RELEASE</version>
           </dependency>
           <dependency>
               <groupId>org.springframework.boot</groupId>
               <artifactId>spring-boot-starter-test</artifactId>
               <scope>test</scope>
               <exclusions>
                   <exclusion>
                       <groupId>org.junit.vintage</groupId>
                       <artifactId>junit-vintage-engine</artifactId>
                   </exclusion>
               </exclusions>
           </dependency>
           
           <!--devtools热部署-->
           <dependency>
               <groupId>org.springframework.boot</groupId>
               <artifactId>spring-boot-devtools</artifactId>
               <optional>true</optional>
               <scope>true</scope>
           </dependency>
       </dependencies>
       
       <build>
           <defaultGoal>compile</defaultGoal>
           <plugins>
               <plugin>
                   <groupId>org.springframework.boot</groupId>
                   <artifactId>spring-boot-maven-plugin</artifactId>
                   <configuration>
                       <includeSystemScope>true</includeSystemScope>
                   </configuration>
               </plugin>
           </plugins>
       </build>
   </project>

    

2. 启动类的增加SpringBoot2Application2

   package com.example.demo;
   ​
   /**
    * @author felix_cai
    *
    */
   import org.springframework.boot.SpringApplication;
   import org.springframework.boot.autoconfigure.SpringBootApplication;
   import org.springframework.cloud.netflix.eureka.server.EnableEurekaServer;
   ​
   @SpringBootApplication
   @EnableEurekaServer
   public class SpringBoot2Application2 {
       public static void main(String[] args) {
           SpringApplication.run(SpringBoot2Application2.class, args);
       }
   }

    

3. 修改application.properties文件

   # 要注册的服务名
   spring.application.name=EurekaServer
   # 端口
   server.port=8761
   #不向注册中心注册实例，因为该实例本身就是注册中心
   eureka.client.register-with-eureka=false
   #不从Eureka Server 中获取实例信息
   eureka.client.fetch-registry=false

4. 启动服务

   http://127.0.0.1:8761/

创建Eureka Provider

1. 修改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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
       <modelVersion>4.0.0</modelVersion>
       <parent>
           <groupId>org.springframework.boot</groupId>
           <artifactId>spring-boot-starter-parent</artifactId>
           <version>2.3.5.RELEASE</version>
           <relativePath/> <!-- lookup parent from repository -->
       </parent>
       <groupId>com.example</groupId>
       <artifactId>demo</artifactId>
       <version>0.0.1-SNAPSHOT</version>
       <name>spring-boot2</name>
       <description>Demo project for Spring Boot</description>
   ​
       <properties>
           <java.version>8</java.version>
           <spring-cloud.version>Finchley.RELEASE</spring-cloud.version>
       </properties>
       <dependencies>
           <dependency>
               <groupId>org.springframework.boot</groupId>
               <artifactId>spring-boot-starter-web</artifactId>
           </dependency>
           <dependency>
               <groupId>org.springframework.cloud</groupId>
               <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
               <version>2.2.3.RELEASE</version>
           </dependency>
           <dependency>
               <groupId>org.springframework.boot</groupId>
               <artifactId>spring-boot-starter-test</artifactId>
               <scope>test</scope>
               <exclusions>
                   <exclusion>
                       <groupId>org.junit.vintage</groupId>
                       <artifactId>junit-vintage-engine</artifactId>
                   </exclusion>
               </exclusions>
           </dependency>
           
           <!--devtools热部署-->
           <dependency>
               <groupId>org.springframework.boot</groupId>
               <artifactId>spring-boot-devtools</artifactId>
               <optional>true</optional>
               <scope>true</scope>
           </dependency>
       </dependencies>
       <build>
           <defaultGoal>compile</defaultGoal>
           <plugins>
               <plugin>
                   <groupId>org.springframework.boot</groupId>
                   <artifactId>spring-boot-maven-plugin</artifactId>
                   <configuration>
                       <includeSystemScope>true</includeSystemScope>
                   </configuration>
               </plugin>
           </plugins>
       </build>
   </project>

    

2. 修改application.properties文件

   # 要注册的服务名
   spring.application.name=Eureka-provider
   # 端口
   server.port=8762
   #Eureka Server地址信息
   eureka.client.service-url.defaultZone=http://localhost:8761/eureka