SpringCloud——Zookeeper（注册中心）

小咪咪 2021-06-24 16:00 496阅读 0赞

### 一、zookeeper简介 ###

ZooKeeper是一个[分布式][Link 1]的，开放源码的[分布式应用程序][Link 2]协调服务，是[Google][]的Chubby一个[开源][Link 3]的实现，是Hadoop和Hbase的重要组件。它是一个为分布式应用提供一致性服务的软件，提供的功能包括：配置维护、域名服务、分布式同步、组服务等。

ZooKeeper的目标就是封装好复杂易出错的关键服务，将简单易用的接口和性能高效、功能稳定的系统提供给用户。

**原理：**

ZooKeeper是以Fast Paxos算法为基础的，[Paxos 算法][Paxos]存在[活锁][Link 4]的问题，即当有多个proposer交错提交时，有可能互相排斥导致没有一个proposer能提交成功，而Fast Paxos作了一些优化，通过选举产生一个leader (领导者)，只有leader才能提交proposer，具体算法可见Fast Paxos。因此，要想弄懂ZooKeeper首先得对Fast Paxos有所了解。

ZooKeeper的基本运转流程：

*  1、选举Leader；
 *  2、同步数据；
 *  3、选举Leader过程中算法有很多，但要达到的选举标准是一致的；
 *  4、Leader要具有最高的执行ID，类似root权限；
 *  5、集群中大多数的机器得到响应并接受选出的Leader。

### 二、Zookeeper作为注册中心搭建SpringCloud实现服务注册及发现 ###

**1、创建工程，父pom.xml依赖文件**

<?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.demo</groupId>
    	<artifactId>springcloud-zookeeper</artifactId>
    	<version>0.0.1-SNAPSHOT</version>
    	<packaging>pom</packaging>
    
    	<name>springcloud-zookeeper</name>
    
    	<parent>
    		<groupId>org.springframework.boot</groupId>
    		<artifactId>spring-boot-starter-parent</artifactId>
    		<version>1.4.5.RELEASE</version>
    	</parent>
    
    	<modules>
    		<module>zookeeper-server</module>
    		<module>zookeeper-client</module>
    	</modules>
    
    	<properties>
    		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    		<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
    		<java.version>1.8</java.version>
    		<spring-cloud.version>Camden.SR7</spring-cloud.version>
    	</properties>
    
    	<dependencies>
    		<dependency>
    			<groupId>org.springframework.boot</groupId>
    			<artifactId>spring-boot-starter</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>${spring-cloud.version}</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>

**2、服务提供者**

pom.xml依赖文件：

<?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.demo.zookeeper</groupId>
    	<artifactId>zookeeper-server</artifactId>
    	<version>0.0.1-SNAPSHOT</version>
    	<packaging>jar</packaging>
    
    	<name>zookeeper-server</name>
    	<description></description>
    
    	<parent>
    		<groupId>com.example.demo</groupId>
    		<artifactId>springcloud-zookeeper</artifactId>
    		<version>0.0.1-SNAPSHOT</version>
    	</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</artifactId>
    		</dependency>
    		
    		<dependency>
    			<groupId>org.springframework.boot</groupId>
    			<artifactId>spring-boot-starter-actuator</artifactId>
    		</dependency>
    
    		<dependency>
    			<groupId>org.springframework.cloud</groupId>
    			<artifactId>spring-cloud-starter-hystrix</artifactId>
    		</dependency>
    
    		<dependency>
    			<groupId>org.springframework.cloud</groupId>
    			<artifactId>spring-cloud-starter-ribbon</artifactId>
    		</dependency>
    
    		<dependency>
    			<groupId>org.springframework.cloud</groupId>
    			<artifactId>spring-cloud-starter-zookeeper-discovery</artifactId>
    		</dependency>
    
    		<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>
    	</dependencies>
    
    	<build>
    		<plugins>
    			<plugin>
    				<groupId>org.springframework.boot</groupId>
    				<artifactId>spring-boot-maven-plugin</artifactId>
    			</plugin>
    		</plugins>
    	</build>
    
    
    </project>

application.yml配置文件：

server:
      port: 8081
    
    spring:
      application:
        name: zookeeper-server
      cloud:
        zookeeper:
          connect-string: localhost:2181
          discovery:
            enabled: true
            register: true

暴露接口：

package com.example.demo.zookeeper.controller;
    
    import org.slf4j.Logger;
    import org.slf4j.LoggerFactory;
    import org.springframework.web.bind.annotation.GetMapping;
    import org.springframework.web.bind.annotation.RestController;
    
    import java.util.UUID;
    
    /**
     * 路径：com.example.demo.zookeeper.controller
     * 类名：
     * 功能：《用一句描述一下》
     * 备注：
     * 创建人：typ
     * 创建时间：2018/9/25 21:19
     * 修改人：
     * 修改备注：
     * 修改时间：
     */
    @RestController
    public class TestController {
    
        private static final Logger log = LoggerFactory.getLogger(TestController.class);
    
        private static final UUID INSTANCE_UUID = UUID.randomUUID();
    
    
        @GetMapping("/test")
        public String test(){
            log.info("test :" + INSTANCE_UUID.toString());
            return INSTANCE_UUID.toString();
        }
    }

启动类添加注解@EnableDiscoveryClient标注为服务发现注解

package com.example.demo.zookeeper;
    
    import org.springframework.boot.SpringApplication;
    import org.springframework.boot.autoconfigure.SpringBootApplication;
    import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
    
    @SpringBootApplication
    @EnableDiscoveryClient
    public class ZookeeperServerApplication {
    
    	public static void main(String[] args) {
    		SpringApplication.run(ZookeeperServerApplication.class, args);
    	}
    }

**3、服务消费者**

pom.xml依赖文件：

<?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.demo.zookeeper</groupId>
    	<artifactId>zookeeper-client</artifactId>
    	<version>0.0.1-SNAPSHOT</version>
    	<packaging>jar</packaging>
    
    	<name>zookeeper-client</name>
    
    	<parent>
    		<groupId>com.example.demo</groupId>
    		<artifactId>springcloud-zookeeper</artifactId>
    		<version>0.0.1-SNAPSHOT</version>
    	</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</artifactId>
    		</dependency>
    
    		<dependency>
    			<groupId>org.springframework.boot</groupId>
    			<artifactId>spring-boot-starter-actuator</artifactId>
    		</dependency>
    
    		<dependency>
    			<groupId>org.springframework.cloud</groupId>
    			<artifactId>spring-cloud-starter-hystrix</artifactId>
    		</dependency>
    
    		<dependency>
    			<groupId>org.springframework.cloud</groupId>
    			<artifactId>spring-cloud-starter-ribbon</artifactId>
    		</dependency>
    
    		<dependency>
    			<groupId>org.springframework.cloud</groupId>
    			<artifactId>spring-cloud-starter-zookeeper-discovery</artifactId>
    		</dependency>
    
    		<dependency>
    			<groupId>org.springframework.boot</groupId>
    			<artifactId>spring-boot-starter-web</artifactId>
    		</dependency>
    
    		<dependency>
    			<groupId>org.springframework.cloud</groupId>
    			<artifactId>spring-cloud-starter-feign</artifactId>
    		</dependency>
    
    		<dependency>
    			<groupId>org.springframework.boot</groupId>
    			<artifactId>spring-boot-starter-test</artifactId>
    			<scope>test</scope>
    		</dependency>
    	</dependencies>
    
    	<build>
    		<plugins>
    			<plugin>
    				<groupId>org.springframework.boot</groupId>
    				<artifactId>spring-boot-maven-plugin</artifactId>
    			</plugin>
    		</plugins>
    	</build>
    
    
    </project>

application.yml配置文件：

server:
      port: 8082
    
    spring:
      application:
        name: zookeeper-client
      cloud:
        zookeeper:
          connect-string: localhost:2181
          discovery:
            enabled: true
            register: false

基于Feign的实现接口

package com.example.demo.zookeeper.service;
    
    import com.example.demo.zookeeper.service.fallback.FeignFallback;
    import org.springframework.cloud.netflix.feign.FeignClient;
    import org.springframework.web.bind.annotation.RequestMapping;
    import org.springframework.web.bind.annotation.RequestMethod;
    
    /**
     * 路径：com.example.demo.zookeeper.service
     * 类名：
     * 功能：《用一句描述一下》
     * 备注：
     * 创建人：typ
     * 创建时间：2018/9/25 21:39
     * 修改人：
     * 修改备注：
     * 修改时间：
     */
    @FeignClient(value = "zookeeper-server",fallback = FeignFallback.class)
    public interface FeignService {
    
        @RequestMapping(value = "/test",method = RequestMethod.GET)
        public String test();
    }

fallback为断路器回调：

package com.example.demo.zookeeper.service.fallback;
    
    import com.example.demo.zookeeper.service.FeignService;
    import org.springframework.stereotype.Component;
    
    /**
     * 路径：com.example.demo.zookeeper.service.fallback
     * 类名：
     * 功能：《用一句描述一下》
     * 备注：
     * 创建人：typ
     * 创建时间：2018/9/25 21:49
     * 修改人：
     * 修改备注：
     * 修改时间：
     */
    @Component
    public class FeignFallback implements FeignService {
    
        @Override
        public String test() {
            return "servie error!";
        }
    }

消费服务：

package com.example.demo.zookeeper.controller;
    
    import com.example.demo.zookeeper.service.FeignService;
    import org.slf4j.Logger;
    import org.slf4j.LoggerFactory;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.web.bind.annotation.GetMapping;
    import org.springframework.web.bind.annotation.RestController;
    
    import java.util.UUID;
    
    /**
     * 路径：com.example.demo.zookeeper.controller
     * 类名：
     * 功能：《用一句描述一下》
     * 备注：
     * 创建人：typ
     * 创建时间：2018/9/25 21:43
     * 修改人：
     * 修改备注：
     * 修改时间：
     */
    @RestController
    public class TestController {
    
        private static final Logger log = LoggerFactory.getLogger(TestController.class);
    
        private static final UUID INSTANCE_UUID = UUID.randomUUID();
    
        @Autowired
        private FeignService feignService;
    
        @GetMapping("/test")
        public String test(){
            log.info("test :" +INSTANCE_UUID.toString());
            return feignService.test();
        }
    }

启动类添加注解@EnableCircuitBreaker为断路器的支持，@EnableFeignClients为Feign客户端的支持。

package com.example.demo.zookeeper;
    
    import org.springframework.boot.SpringApplication;
    import org.springframework.boot.autoconfigure.SpringBootApplication;
    import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
    import org.springframework.cloud.netflix.feign.EnableFeignClients;
    
    @SpringBootApplication
    @EnableDiscoveryClient
    @EnableFeignClients
    public class ZookeeperClientApplication {
    
    	public static void main(String[] args) {
    		SpringApplication.run(ZookeeperClientApplication.class, args);
    	}
    }

启动工程，访问 [http://localhost:8082/test][http_localhost_8082_test]，浏览显示：

09969381-2857-455c-b9f2-6fd5d3d25b16

消费者接口日志显示：

2018-09-26 10:27:32.195  INFO 12176 --- [nio-8082-exec-1] c.e.d.z.controller.TestController        : test :ae5bdfce-887d-433f-a90a-cb4b8a1f109d

服务者接口日志显示：

2018-09-26 10:27:33.188  INFO 8204 --- [nio-8081-exec-1] c.e.d.z.controller.TestController        : test :09969381-2857-455c-b9f2-6fd5d3d25b16

源码下载：[https://download.csdn.net/download/typ1805/10687809][https_download.csdn.net_download_typ1805_10687809]

[Link 1]: https://baike.baidu.com/item/%E5%88%86%E5%B8%83%E5%BC%8F/19276232
[Link 2]: https://baike.baidu.com/item/%E5%88%86%E5%B8%83%E5%BC%8F%E5%BA%94%E7%94%A8%E7%A8%8B%E5%BA%8F/9854429
[Google]: https://baike.baidu.com/item/Google
[Link 3]: https://baike.baidu.com/item/%E5%BC%80%E6%BA%90/246339
[Paxos]: https://baike.baidu.com/item/Paxos%20%E7%AE%97%E6%B3%95
[Link 4]: https://baike.baidu.com/item/%E6%B4%BB%E9%94%81
[http_localhost_8082_test]: http://localhost:8082/test
[https_download.csdn.net_download_typ1805_10687809]: https://download.csdn.net/download/typ1805/10687809