SpringCloud——Zookeeper（注册中心）

小咪咪 2021-06-24 16:00 673阅读 0赞

一、zookeeper简介

  1.     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。
  3.     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：

  1.     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

  1. <?xml version="1.0" encoding="UTF-8"?>
  2. <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  3.     xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
  4.     <modelVersion>4.0.0</modelVersion>
  6.     <groupId>com.example.demo</groupId>
  7.     <artifactId>springcloud-zookeeper</artifactId>
  8.     <version>0.0.1-SNAPSHOT</version>
  9.     <packaging>pom</packaging>
  11.     <name>springcloud-zookeeper</name>
  13.     <parent>
  14.         <groupId>org.springframework.boot</groupId>
  15.         <artifactId>spring-boot-starter-parent</artifactId>
  16.         <version>1.4.5.RELEASE</version>
  17.     </parent>
  19.     <modules>
  20.         <module>zookeeper-server</module>
  21.         <module>zookeeper-client</module>
  22.     </modules>
  24.     <properties>
  25.         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
  26.         <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
  27.         <java.version>1.8</java.version>
  28.         <spring-cloud.version>Camden.SR7</spring-cloud.version>
  29.     </properties>
  31.     <dependencies>
  32.         <dependency>
  33.             <groupId>org.springframework.boot</groupId>
  34.             <artifactId>spring-boot-starter</artifactId>
  35.         </dependency>
  37.         <dependency>
  38.             <groupId>org.springframework.boot</groupId>
  39.             <artifactId>spring-boot-starter-test</artifactId>
  40.             <scope>test</scope>
  41.         </dependency>
  42.     </dependencies>
  44.     <dependencyManagement>
  45.         <dependencies>
  46.             <dependency>
  47.                 <groupId>org.springframework.cloud</groupId>
  48.                 <artifactId>spring-cloud-dependencies</artifactId>
  49.                 <version>${spring-cloud.version}</version>
  50.                 <type>pom</type>
  51.                 <scope>import</scope>
  52.             </dependency>
  53.         </dependencies>
  54.     </dependencyManagement>
  56.     <build>
  57.         <plugins>
  58.             <plugin>
  59.                 <groupId>org.springframework.boot</groupId>
  60.                 <artifactId>spring-boot-maven-plugin</artifactId>
  61.             </plugin>
  62.         </plugins>
  63.     </build>
  66. </project>

2、服务提供者

pom.xml依赖文件：

  1. <?xml version="1.0" encoding="UTF-8"?>
  2. <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  3.     xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
  4.     <modelVersion>4.0.0</modelVersion>
  6.     <groupId>com.example.demo.zookeeper</groupId>
  7.     <artifactId>zookeeper-server</artifactId>
  8.     <version>0.0.1-SNAPSHOT</version>
  9.     <packaging>jar</packaging>
  11.     <name>zookeeper-server</name>
  12.     <description></description>
  14.     <parent>
  15.         <groupId>com.example.demo</groupId>
  16.         <artifactId>springcloud-zookeeper</artifactId>
  17.         <version>0.0.1-SNAPSHOT</version>
  18.     </parent>
  20.     <properties>
  21.         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
  22.         <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
  23.         <java.version>1.8</java.version>
  24.     </properties>
  26.     <dependencies>
  27.         <dependency>
  28.             <groupId>org.springframework.boot</groupId>
  29.             <artifactId>spring-boot-starter</artifactId>
  30.         </dependency>
  32.         <dependency>
  33.             <groupId>org.springframework.boot</groupId>
  34.             <artifactId>spring-boot-starter-actuator</artifactId>
  35.         </dependency>
  37.         <dependency>
  38.             <groupId>org.springframework.cloud</groupId>
  39.             <artifactId>spring-cloud-starter-hystrix</artifactId>
  40.         </dependency>
  42.         <dependency>
  43.             <groupId>org.springframework.cloud</groupId>
  44.             <artifactId>spring-cloud-starter-ribbon</artifactId>
  45.         </dependency>
  47.         <dependency>
  48.             <groupId>org.springframework.cloud</groupId>
  49.             <artifactId>spring-cloud-starter-zookeeper-discovery</artifactId>
  50.         </dependency>
  52.         <dependency>
  53.             <groupId>org.springframework.boot</groupId>
  54.             <artifactId>spring-boot-starter-web</artifactId>
  55.         </dependency>
  57.         <dependency>
  58.             <groupId>org.springframework.boot</groupId>
  59.             <artifactId>spring-boot-starter-test</artifactId>
  60.             <scope>test</scope>
  61.         </dependency>
  62.     </dependencies>
  64.     <build>
  65.         <plugins>
  66.             <plugin>
  67.                 <groupId>org.springframework.boot</groupId>
  68.                 <artifactId>spring-boot-maven-plugin</artifactId>
  69.             </plugin>
  70.         </plugins>
  71.     </build>
  74. </project>

application.yml配置文件：

  1. server:
  2.   port: 8081
  4. spring:
  5.   application:
  6.     name: zookeeper-server
  7.   cloud:
  8.     zookeeper:
  9.       connect-string: localhost:2181
  10.       discovery:
  11.         enabled: true
  12.         register: true

暴露接口：

  1. package com.example.demo.zookeeper.controller;
  3. import org.slf4j.Logger;
  4. import org.slf4j.LoggerFactory;
  5. import org.springframework.web.bind.annotation.GetMapping;
  6. import org.springframework.web.bind.annotation.RestController;
  8. import java.util.UUID;
  10. /**
  11.  * 路径：com.example.demo.zookeeper.controller
  12.  * 类名：
  13.  * 功能：《用一句描述一下》
  14.  * 备注：
  15.  * 创建人：typ
  16.  * 创建时间：2018/9/25 21:19
  17.  * 修改人：
  18.  * 修改备注：
  19.  * 修改时间：
  20.  */
  21. @RestController
  22. public class TestController {
  24.     private static final Logger log = LoggerFactory.getLogger(TestController.class);
  26.     private static final UUID INSTANCE_UUID = UUID.randomUUID();
  29.     @GetMapping("/test")
  30.     public String test(){
  31.         log.info("test :" + INSTANCE_UUID.toString());
  32.         return INSTANCE_UUID.toString();
  33.     }
  34. }

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

  1. package com.example.demo.zookeeper;
  3. import org.springframework.boot.SpringApplication;
  4. import org.springframework.boot.autoconfigure.SpringBootApplication;
  5. import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
  7. @SpringBootApplication
  8. @EnableDiscoveryClient
  9. public class ZookeeperServerApplication {
  11.     public static void main(String[] args) {
  12.         SpringApplication.run(ZookeeperServerApplication.class, args);
  13.     }
  14. }

3、服务消费者

pom.xml依赖文件：

  1. <?xml version="1.0" encoding="UTF-8"?>
  2. <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  3.     xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
  4.     <modelVersion>4.0.0</modelVersion>
  6.     <groupId>com.example.demo.zookeeper</groupId>
  7.     <artifactId>zookeeper-client</artifactId>
  8.     <version>0.0.1-SNAPSHOT</version>
  9.     <packaging>jar</packaging>
  11.     <name>zookeeper-client</name>
  13.     <parent>
  14.         <groupId>com.example.demo</groupId>
  15.         <artifactId>springcloud-zookeeper</artifactId>
  16.         <version>0.0.1-SNAPSHOT</version>
  17.     </parent>
  19.     <properties>
  20.         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
  21.         <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
  22.         <java.version>1.8</java.version>
  23.     </properties>
  25.     <dependencies>
  26.         <dependency>
  27.             <groupId>org.springframework.boot</groupId>
  28.             <artifactId>spring-boot-starter</artifactId>
  29.         </dependency>
  31.         <dependency>
  32.             <groupId>org.springframework.boot</groupId>
  33.             <artifactId>spring-boot-starter-actuator</artifactId>
  34.         </dependency>
  36.         <dependency>
  37.             <groupId>org.springframework.cloud</groupId>
  38.             <artifactId>spring-cloud-starter-hystrix</artifactId>
  39.         </dependency>
  41.         <dependency>
  42.             <groupId>org.springframework.cloud</groupId>
  43.             <artifactId>spring-cloud-starter-ribbon</artifactId>
  44.         </dependency>
  46.         <dependency>
  47.             <groupId>org.springframework.cloud</groupId>
  48.             <artifactId>spring-cloud-starter-zookeeper-discovery</artifactId>
  49.         </dependency>
  51.         <dependency>
  52.             <groupId>org.springframework.boot</groupId>
  53.             <artifactId>spring-boot-starter-web</artifactId>
  54.         </dependency>
  56.         <dependency>
  57.             <groupId>org.springframework.cloud</groupId>
  58.             <artifactId>spring-cloud-starter-feign</artifactId>
  59.         </dependency>
  61.         <dependency>
  62.             <groupId>org.springframework.boot</groupId>
  63.             <artifactId>spring-boot-starter-test</artifactId>
  64.             <scope>test</scope>
  65.         </dependency>
  66.     </dependencies>
  68.     <build>
  69.         <plugins>
  70.             <plugin>
  71.                 <groupId>org.springframework.boot</groupId>
  72.                 <artifactId>spring-boot-maven-plugin</artifactId>
  73.             </plugin>
  74.         </plugins>
  75.     </build>
  78. </project>

application.yml配置文件：

  1. server:
  2.   port: 8082
  4. spring:
  5.   application:
  6.     name: zookeeper-client
  7.   cloud:
  8.     zookeeper:
  9.       connect-string: localhost:2181
  10.       discovery:
  11.         enabled: true
  12.         register: false

基于Feign的实现接口

  1. package com.example.demo.zookeeper.service;
  3. import com.example.demo.zookeeper.service.fallback.FeignFallback;
  4. import org.springframework.cloud.netflix.feign.FeignClient;
  5. import org.springframework.web.bind.annotation.RequestMapping;
  6. import org.springframework.web.bind.annotation.RequestMethod;
  8. /**
  9.  * 路径：com.example.demo.zookeeper.service
  10.  * 类名：
  11.  * 功能：《用一句描述一下》
  12.  * 备注：
  13.  * 创建人：typ
  14.  * 创建时间：2018/9/25 21:39
  15.  * 修改人：
  16.  * 修改备注：
  17.  * 修改时间：
  18.  */
  19. @FeignClient(value = "zookeeper-server",fallback = FeignFallback.class)
  20. public interface FeignService {
  22.     @RequestMapping(value = "/test",method = RequestMethod.GET)
  23.     public String test();
  24. }

fallback为断路器回调：

  1. package com.example.demo.zookeeper.service.fallback;
  3. import com.example.demo.zookeeper.service.FeignService;
  4. import org.springframework.stereotype.Component;
  6. /**
  7.  * 路径：com.example.demo.zookeeper.service.fallback
  8.  * 类名：
  9.  * 功能：《用一句描述一下》
  10.  * 备注：
  11.  * 创建人：typ
  12.  * 创建时间：2018/9/25 21:49
  13.  * 修改人：
  14.  * 修改备注：
  15.  * 修改时间：
  16.  */
  17. @Component
  18. public class FeignFallback implements FeignService {
  20.     @Override
  21.     public String test() {
  22.         return "servie error!";
  23.     }
  24. }

消费服务：

  1. package com.example.demo.zookeeper.controller;
  3. import com.example.demo.zookeeper.service.FeignService;
  4. import org.slf4j.Logger;
  5. import org.slf4j.LoggerFactory;
  6. import org.springframework.beans.factory.annotation.Autowired;
  7. import org.springframework.web.bind.annotation.GetMapping;
  8. import org.springframework.web.bind.annotation.RestController;
  10. import java.util.UUID;
  12. /**
  13.  * 路径：com.example.demo.zookeeper.controller
  14.  * 类名：
  15.  * 功能：《用一句描述一下》
  16.  * 备注：
  17.  * 创建人：typ
  18.  * 创建时间：2018/9/25 21:43
  19.  * 修改人：
  20.  * 修改备注：
  21.  * 修改时间：
  22.  */
  23. @RestController
  24. public class TestController {
  26.     private static final Logger log = LoggerFactory.getLogger(TestController.class);
  28.     private static final UUID INSTANCE_UUID = UUID.randomUUID();
  30.     @Autowired
  31.     private FeignService feignService;
  33.     @GetMapping("/test")
  34.     public String test(){
  35.         log.info("test :" +INSTANCE_UUID.toString());
  36.         return feignService.test();
  37.     }
  38. }

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

  1. package com.example.demo.zookeeper;
  3. import org.springframework.boot.SpringApplication;
  4. import org.springframework.boot.autoconfigure.SpringBootApplication;
  5. import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
  6. import org.springframework.cloud.netflix.feign.EnableFeignClients;
  8. @SpringBootApplication
  9. @EnableDiscoveryClient
  10. @EnableFeignClients
  11. public class ZookeeperClientApplication {
  13.     public static void main(String[] args) {
  14.         SpringApplication.run(ZookeeperClientApplication.class, args);
  15.     }
  16. }

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

  1. 09969381-2857-455c-b9f2-6fd5d3d25b16

消费者接口日志显示：

  1. 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：

  1. 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

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