zookeeper watcher实现服务注册 zookeeper实现注册中心

一、zookeeper简介

        ZooKeeper是一个分布式的，开放源码的分布式应用程序协调服务，是Google的Chubby一个开源的实现，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 算法存在活锁的问题，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，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