Eureka实现注册中心

CAP原则又称CAP定理，指的是在一个分布式系统中，Consistency（一致性）、 Availability（可用性）、Partition tolerance（分区容错性），三者不可得兼。它是分布式系统中最核心最重要的理论。

分布式系统的CAP理论：理论首先把分布式系统中的三个特性进行了如下归纳：

l 一致性（C）：在分布式系统中的所有数据备份，在同一时刻是否同样的值。（等同于所有节点访问同一份最新的数据副本）

l 可用性（A）：在集群中一部分节点故障后，集群整体是否还能响应客户端的读写请求。（对数据更新具备高可用性）

l 分区容错性（P）：以实际效果而言，分区相当于对通信的时限要求。系统如果不能在时限内达成数据一致性，就意味着发生了分区的情况，必须就当前操作在C和A之间做出选择。

ZooKeeper和Eureka对比

ZooKeeper基于CP，不保证高可用，如果zookeeper正在选主，或者Zookeeper集群中半数以上机器不可用，那么将无法获得数据。Eureka基于AP，能保证高可用，即使所有机器都挂了，也能拿到本地缓存的数据。作为注册中心，其实配置是不经常变动的，只有发版（发布新的版本）和机器出故障时会变。对于不经常变动的配置来说，CP是不合适的，而AP在遇到问题时可以用牺牲一致性来保证可用性，既返回旧数据，缓存数据。

所以理论上Eureka是更适合作注册中心。而现实环境中大部分项目可能会使用ZooKeeper，那是因为集群不够大，并且基本不会遇到用做注册中心的机器一半以上都挂了的情况。所以实际上也没什么大问题。

Eureka部署服务端、提供端、消费端（消费者整合负载均衡Ribbon，提供方整合Mybaits）

服务端：

搭建SpringBoot项目

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>

    <groupId>eureka.server</groupId>

    <artifactId>eureka-server</artifactId>

    <version>0.0.1-SNAPSHOT</version>

    <parent>

        <groupId>org.springframework.boot</groupId>

        <artifactId>spring-boot-starter-parent</artifactId>

        <version>1.5.9.RELEASE</version>

        <relativePath />

    </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.cloud</groupId>

            <artifactId>spring-cloud-starter-eureka-server</artifactId>

        </dependency>

    </dependencies>

    <dependencyManagement>

        <dependencies>

            <dependency>

                <groupId>org.springframework.cloud</groupId>

                <artifactId>spring-cloud-dependencies</artifactId>

                <version>Dalston.SR1</version>

                <type>pom</type>

                <scope>import</scope>

            </dependency>

        </dependencies>

    </dependencyManagement>

</project>

application.yml

security:

  basic:

    enabled: true

  user:

    name: user

    password: password123

server:

  port: 8761

eureka:

  client:

    register-with-eureka: false

    fetch-registry: false

    service-url:

      defaultZone: http://user:password123@localhost:8761/eureka

logging:

  level:

    root: INFO

　　RunAppEureka.java

import org.springframework.boot.SpringApplication;

import org.springframework.boot.autoconfigure.SpringBootApplication;

import org.springframework.cloud.netflix.eureka.server.EnableEurekaServer;

@SpringBootApplication

@EnableEurekaServer

public class RunAppEureka {

	public static void main(String[] args) {

        SpringApplication.run(RunAppEureka.class, args);

	}

}

　　提供方1(加入整合SpringBoot整合Mybatis)

<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>eureka.provider</groupId>

    <artifactId>eureka-provider</artifactId>

    <version>0.0.1-SNAPSHOT</version>

    <parent>

        <groupId>org.springframework.boot</groupId>

        <artifactId>spring-boot-starter-parent</artifactId>

        <version>1.5.9.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>

        <impala.jdbc.version>2.5.30</impala.jdbc.version>

    </properties>

    <dependencies>

        <dependency>

            <groupId>org.springframework.cloud</groupId>

            <artifactId>spring-cloud-starter-eureka</artifactId>

        </dependency>

        <dependency>

            <groupId>org.mybatis.spring.boot</groupId>

            <artifactId>mybatis-spring-boot-starter</artifactId>

            <version>1.3.0</version>

        </dependency>

        <dependency>

            <groupId>org.springframework.boot</groupId>

            <artifactId>spring-boot-starter-web</artifactId>

        </dependency>

        <dependency>

            <groupId>com.alibaba</groupId>

            <artifactId>druid</artifactId>

            <version>1.1.12</version>

        </dependency>

        <dependency>

            <groupId>com.oracle</groupId>

            <artifactId>ojdbc6</artifactId>

            <version>11.2.0.3</version>

        </dependency>

    </dependencies>

    <dependencyManagement>

        <dependencies>

            <dependency>

                <groupId>org.springframework.cloud</groupId>

                <artifactId>spring-cloud-dependencies</artifactId>

                <version>Dalston.SR1</version>

                <type>pom</type>

                <scope>import</scope>

            </dependency>

        </dependencies>

    </dependencyManagement>

</project>

application.yml

server:

  port: 7900

spring:

  application:

    name: provider-user

  datasource:

    type: com.alibaba.druid.pool.DruidDataSource

    driver-class-name: oracle.jdbc.OracleDriver

    url: jdbc:oracle:thin:@(DESCRIPTION=(ADDRESS_LIST=(ADDRESS=(PROTOCOL=TCP)(HOST=172.24.7.177)(PORT=1521)))(CONNECT_DATA=(SERVICE_NAME=iovdb)))

    username: foton

    password: foton[zk]

mybatis:

  typeAliasesPackage: cn.hz.pojo

  mapperLocations: classpath:mappers/*.xml

eureka:

  client:

    serviceUrl:

      defaultZone: http://user:password123@localhost:8761/eureka

logging:

  level:

    root: INFO

ProviderRunApp.java

import org.mybatis.spring.annotation.MapperScan;

import org.springframework.boot.SpringApplication;

import org.springframework.boot.autoconfigure.SpringBootApplication;

import org.springframework.cloud.netflix.eureka.EnableEurekaClient;

@SpringBootApplication

@EnableEurekaClient

@MapperScan("cn.hz.mapper")

public class ProviderRunApp {

	public static void main(String[] args) {

		SpringApplication.run(ProviderRunApp.class, args);

	}

}

User.java

import java.io.Serializable;

import java.util.Date;

import org.springframework.format.annotation.DateTimeFormat;

import com.fasterxml.jackson.annotation.JsonFormat;

public class User implements Serializable {

	/**

	 *

	 */

	private static final long serialVersionUID = 8693407369491314806L;

	/*

	 * id NUMBER(19) not null, created TIMESTAMP(6), modified TIMESTAMP(6),

	 * description VARCHAR2(255 CHAR), name VARCHAR2(255 CHAR),

	 * cbm_mag_company_id NUMBER(19), category_id NUMBER(19), cbm_mag_user_id

	 * NUMBER(19), layout CLOB

	 */

	private Long id;

	@DateTimeFormat(pattern="yyyy-MM-dd HH:mm:ss")

    @JsonFormat(

            pattern = "yyyy-MM-dd HH:mm:ss"

    )

	private Date created;

	@DateTimeFormat(pattern="yyyy-MM-dd HH:mm:ss")

    @JsonFormat(

            pattern = "yyyy-MM-dd HH:mm:ss"

    )

	private Date modified;

	private String description;

	private String name;

	private int sort;

	private Long companyId;

	private Long userId;

	private Long parentId;

	getter setter。。。

	@Override

	public String toString() {

		return "User [id=" + id + ", created=" + created + ", modified=" + modified + ", description=" + description

				+ ", name=" + name + ", sort=" + sort + ", companyid=" + companyId + ", userId=" + userId

				+ ", parentId=" + parentId + "]";

	}

UserMapper.java

import java.util.List;

import org.apache.ibatis.annotations.Param;

import org.apache.ibatis.annotations.Select;

import cn.hz.pojo.User;

//注解和xml方式混合

public interface UserMapper {

	//调用xml方式

    public List<User> find();

    //调用注解方式

    @Select("select id, created, modified, description, name, sort, cbm_mag_company_id as companyId, parent_id as parentId, cbm_mag_user_id as userId from IOV_DASH_CATEGORY where id=#{id}")

	public User get(@Param("id") Long id);

}

　　UserService.java

import java.util.List;

import cn.hz.pojo.User;

public interface UserService {

	public List<User> find();

	public User get(Long id);

}

　　UserServiceImpl.java

import java.util.List;

import org.springframework.beans.factory.annotation.Autowired;

import org.springframework.stereotype.Service;

import cn.hz.mapper.UserMapper;

import cn.hz.pojo.User;

@Service

public class UserServiceImpl implements UserService {

@Autowired

private UserMapper userMapper;

public List<User> find() {

return userMapper.find();

}

public User get(Long id) {

return userMapper.get(id);

}

}

　　UserMapper.xml

<?xml version="1.0" encoding="UTF-8"?>

<!DOCTYPE mapper

    PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"

    "http://mybatis.org/dtd/mybatis-3-mapper.dtd">

<!-- namespace命名空间，唯一特性 -->

<mapper namespace="cn.hz.mapper.UserMapper">

    <resultMap type="cn.hz.pojo.User" id="user">

       <id column="id" property="id" jdbcType="BIGINT"/>

       <result column="created" property="created" javaType="java.sql.Date"/>

       <result column="modified" property="modified" javaType="java.sql.Date"/>

       <result column="description" property="description" jdbcType="VARCHAR"/>

       <result column="name" property="name" jdbcType="VARCHAR"/>

       <result column="sort" property="sort" jdbcType="INTEGER"/>

       <result column="companyId" property="cbm_mag_company_id" jdbcType="BIGINT"/>

       <result column="userId" property="cbm_mag_user_id" jdbcType="BIGINT"/>

       <result column="parentId" property="parent_id" jdbcType="BIGINT"/>

    </resultMap>

    <select id="find" resultType="user">

        select id, created, modified, description, name, sort, cbm_mag_company_id as companyId, parent_id as parentId, cbm_mag_user_id as userId from IOV_DASH_CATEGORY

    </select>

</mapper>

UserController.java （为整合MyBatis测试使用）

import org.springframework.beans.factory.annotation.Autowired;

import org.springframework.web.bind.annotation.GetMapping;

import org.springframework.web.bind.annotation.PathVariable;

import org.springframework.web.bind.annotation.RequestMapping;

import org.springframework.web.bind.annotation.RestController;

import cn.hz.pojo.User;

import cn.hz.service.UserService;

@RestController

@RequestMapping(value = "/user")

public class UserController {

	@Autowired

	private UserService userSerivce;

	@GetMapping("/{name}")

	public String getName(@PathVariable String name) {

		return "hello:" + name;

	}

	@GetMapping("/list")

	public String list() {

		return userSerivce.find().toString();

	}

	@GetMapping("/get/{id}")

	public String get(@PathVariable Long id) {

		User user = userSerivce.get(id);

		if (null == user)

			return null;

		else

			return userSerivce.get(id).toString();

	}

}

提供方2和提供方1创建基本相同，此处忽略

消费者：（整合Ribbon调用不同的提供方）

1.1.1 Ribbon

Feign是netflix开发的声明式、模板化的http客户端，在使用时就像调用本地(服务消费者自己)的方法一般，帮助我们更加优雅的调用服务提供者的API。Feign自身支持springMVC，还整合了Eureka、Ribbon，极大的简化了Feign的使用。就整合Euraka而言，只需和普通的服务配置Eureka server的信息即可。整合Ribbon，就意味着不再需要通过标注@LoadBalanced的实例化后的RestTemplate去调用服务提供者方法了。Feign只需通过简单的定义一个接口即可实现负载均衡。

和nginx不同，它是客户端侧负载均衡。

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>

    <groupId>eureka.client</groupId>

    <artifactId>eureka-client</artifactId>

    <version>0.0.1-SNAPSHOT</version>

    <parent>

        <groupId>org.springframework.boot</groupId>

        <artifactId>spring-boot-starter-parent</artifactId>

        <version>1.5.9.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.cloud</groupId>

            <artifactId>spring-cloud-starter-eureka</artifactId>

        </dependency>

        <dependency>

            <groupId>org.springframework.boot</groupId>

            <artifactId>spring-boot-starter-web</artifactId>

        </dependency>

    </dependencies>

    <dependencyManagement>

        <dependencies>

            <dependency>

                <groupId>org.springframework.cloud</groupId>

                <artifactId>spring-cloud-dependencies</artifactId>

                <version>Dalston.SR1</version>

                <type>pom</type>

                <scope>import</scope>

            </dependency>

        </dependencies>

    </dependencyManagement>

</project>

application.yml

server:

  port: 8010

spring:

  application:

    name: consumer-client

eureka:

  client:

    serviceUrl:

      defaultZone: http://user:password123@localhost:8761/eureka

logging:

  level:

    root: INFO

ClientRunApp.java

import org.springframework.boot.SpringApplication;

import org.springframework.boot.autoconfigure.SpringBootApplication;

import org.springframework.cloud.client.loadbalancer.LoadBalanced;

import org.springframework.cloud.netflix.eureka.EnableEurekaClient;

import org.springframework.cloud.netflix.ribbon.RibbonClient;

import org.springframework.context.annotation.Bean;

import org.springframework.web.client.RestTemplate;

@SpringBootApplication

@EnableEurekaClient

@RibbonClient(name="provider-user", configuration=RibbonRuleConfig.class)

public class ClientRunApp {

	@Bean

	@LoadBalanced  //Ribbon负载均衡

	public RestTemplate restTemplate() {

		return new RestTemplate();

	}

	public static void main(String[] args) {

		SpringApplication.run(ClientRunApp.class, args);

	}

}

　　RibbonRuleConfig.java

import org.springframework.context.annotation.Bean;

import org.springframework.context.annotation.Configuration;

import com.netflix.loadbalancer.IRule;

import com.netflix.loadbalancer.RandomRule;

/**

 *

 * 自定义Ribbon配置

 * 规定：这个类不能再@ComponentScan和@SpringBootApplication本包和子包下，否则引起@RibbonClients扫描冲突

 * 注意：随机第一次打断点进入，之后多次刷新就不进入，可能由于本地缓存原因

 */

@Configuration

public class RibbonRuleConfig {

	@Bean

	public IRule ribbonRule(){

		return new RandomRule();

	}

}

　　UserController.java

import org.springframework.beans.factory.annotation.Autowired;

import org.springframework.web.bind.annotation.GetMapping;

import org.springframework.web.bind.annotation.PathVariable;

import org.springframework.web.bind.annotation.ResponseBody;

import org.springframework.web.bind.annotation.RestController;

import org.springframework.web.client.RestTemplate;

@RestController

public class UserController {

	@Autowired

	private RestTemplate restTemplate;

	  @GetMapping("/user/{id}")

	  @ResponseBody

      public String getName(@PathVariable String id) {

		  //String url = "http://localhost:7900/user/"+ name;

		//provider-user就是Eureka中提供服务

			String url = "http://provider-user/user/get/"+id;

    	  return "client:" + this.restTemplate.getForObject(url, String.class);

		  //return url;

      }

}

巴特西

Eureka实现注册中心

ZooKeeper和Eureka对比

Eureka部署服务端、提供端、消费端（消费者整合负载均衡Ribbon，提供方整合Mybaits）

1.1.1 Ribbon

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