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Zookeeper-服务注册与发现

最近在学习zookeeper,作为一个分布式协调服务,它的用途挺多,服务注册与发现、分布式锁、集群选举、配置中心等。今天我先通过一个demo实现zookeeper的服务注册与发现功能

思路

zookeeper服务注册与发现

  • 将产品服务的信息注册到zookeeper的节点上
  • 然后获取到节点上的信息并存储起来(本文存到List)
  • Watcher机制监控List里数据的变化并更新数据 (假如产品服务2挂了通过监听机制将其移出)
  • 利用轮询或者hash等算法去获取List里的数据供订单服务调用(负载均衡)
    zk节点

注册服务

获取到zookeeper的实例并创建根节点和子节点,子节点为临时顺序节点,用于保存服务对应的ip

package com.ooliuyue.product.zk;

import org.apache.zookeeper.CreateMode;
import org.apache.zookeeper.ZooDefs;
import org.apache.zookeeper.ZooKeeper;
import org.apache.zookeeper.data.Stat;


/**
 * @Auther: ly
 * @Date: 2019/4/19 11:53
 */

public class ServiceRegister {

    private  static final String BASE_SERVICE = "/service";
    private  static final String SERVICE_NAME = "/product";

    public static void register(String address,int port) {
        /**
         * 在zk创建根节点path,在根节点下创建临时子节点用于存放服务ip和端口
         */
        try {
            String path = BASE_SERVICE + SERVICE_NAME;
            ZooKeeper zooKeeper = new ZooKeeper("127.0.0.1:2181",5000,(watchedEvent) -> {});
            System.out.println(zooKeeper);
            Thread.sleep(2000);
            Stat exists = zooKeeper.exists(BASE_SERVICE + SERVICE_NAME, false);
            //先判断服务根路径是否存在
            if (exists == null){
                zooKeeper.create(BASE_SERVICE + SERVICE_NAME,"".getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);
            }
            //将服务的ip和端口作为临时带序号的子节点
            String server_path = address+":"+port;
            zooKeeper.create(path + "/child",server_path.getBytes(),ZooDefs.Ids.OPEN_ACL_UNSAFE,CreateMode.EPHEMERAL_SEQUENTIAL);
            System.out.println("product服务注册成功");
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

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容器初始化的时候调用register(),给zk的子节点设置值(服务的url)

package com.ooliuyue.product.listen;

import com.ooliuyue.product.zk.ServiceRegister;

import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;
import java.net.InetAddress;
import java.util.Properties;

/**
 * @Auther: ly
 * @Date: 2019/4/19 10:43
 */

public class InitListener implements ServletContextListener {

    @Override
    //容器初始化的时候会调用
    public void  contextInitialized(ServletContextEvent sce) {
        Properties properties = new Properties();
        try {
            properties.load(InitListener.class.getClassLoader().getResourceAsStream("application.properties"));
            //获得IP
            String hostAddress = InetAddress.getLocalHost().getHostAddress();
            //获得端口
            int port = Integer.valueOf(properties.getProperty("server.port"));
            ServiceRegister.register(hostAddress,port);

        } catch (Exception e) {
            e.printStackTrace();
        }


    }
    public void contextDestroyed(ServletContextEvent sce) {
    }

}

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启动服务,进行测试,前提需要启动ZooKeeper

package com.ooliuyue.product.controller;

import com.ooliuyue.product.pojo.Product;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import javax.servlet.http.HttpServletRequest;

/**
 * @Auther: ly
 * @Date: 2019/4/19 09:52
 */

@RequestMapping("/product")
@RestController
public class ProductController {

    @RequestMapping("/get/{id}")
    public Object getProduct(HttpServletRequest request, @PathVariable("id") String id){
        int localPort = request.getLocalPort();
        return new Product(id,"productName:" + localPort);
    }
}

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两个产品服务启动成功

通过工具查看节点

服务发现

获取zk节点上保存的服务信息并保存到一个List中,watcher机制来监控List中数据的变化

package com.ooliuyue.order.listener;

import com.ooliuyue.order.utils.LoadBalance;
import org.apache.zookeeper.Watcher;
import org.apache.zookeeper.ZooKeeper;
import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;
import java.util.ArrayList;
import java.util.List;

/**
 * @Auther: ly
 * @Date: 2019/4/19 16:26
 */

public class InitListener implements ServletContextListener {

    private  static final String BASE_SERVICE = "/service";
    private  static final String SERVICE_NAME = "/product";
    private ZooKeeper zooKeeper;

    private void init(){
        try {
            //连接zk,获得列表信息
            //watcher机制:监控获取到的服务列表的变化
            zooKeeper = new ZooKeeper("127.0.0.1:2181",5000,(watchedEvent) -> {
                if (watchedEvent.getType() == Watcher.Event.EventType.NodeChildrenChanged
                        && watchedEvent.getPath().equals(BASE_SERVICE+SERVICE_NAME)) {
                    System.out.println("***注册到zk的服务信息发生变化***");
                    updateServerList();
                }
            });
            //第一次连接的时候要返回的列表
            updateServerList();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    private void updateServerList() {
        List<String> list = new ArrayList<>();
        try {
            List<String> children = zooKeeper.getChildren(BASE_SERVICE + SERVICE_NAME,true);
            for(String subNode : children) {
                byte[] data = zooKeeper.getData(BASE_SERVICE + SERVICE_NAME + "/" + subNode, false, null);
                String host  = new String(data,"utf-8");
                list.add(host);
            }
            //将获取的服务端口和IP保存List中
            LoadBalance.SERVICE_LIST = list;
        } catch (Exception e) {
            e.printStackTrace();
        }
    }


    @Override
    public void  contextInitialized(ServletContextEvent sce) {
        init();
    }

    @Override
    public void contextDestroyed(ServletContextEvent sce) {
    }


}

复制代码

通过实现一个随机算法获取到产品服务,供订单服务调用(相当于负载)

package com.ooliuyue.order.utils;

import java.util.List;

/**
 * @Auther: ly
 * @Date: 2019/4/22 14:00
 */

public abstract class LoadBalance {

    public volatile static List<String> SERVICE_LIST;

    public abstract String chooseServiceHost();
}

复制代码
package com.ooliuyue.order.utils;

import org.springframework.util.CollectionUtils;

import java.util.Random;

/**
 * @Auther: ly
 * @Date: 2019/4/22 14:02
 */

//实现了一个随机的算法(随机获取订单服务)
public class RandomLoadBalance extends LoadBalance {


    @Override
    public String chooseServiceHost() {
        String result = "";
        if (!CollectionUtils.isEmpty(SERVICE_LIST)) {
            int nextInt = new Random().nextInt(SERVICE_LIST.size());
            result = SERVICE_LIST.get(nextInt);
        }
        return result;
    }
}

复制代码

测试调用结果

package com.ooliuyue.order.controller;

import com.ooliuyue.order.pojo.Order;
import com.ooliuyue.order.utils.LoadBalance;
import com.ooliuyue.order.utils.RandomLoadBalance;
import com.ooliuyue.product.pojo.Product;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.client.RestTemplate;

import javax.annotation.Resource;
import javax.servlet.http.HttpServletRequest;

/**
 * @Auther: ly
 * @Date: 2019/4/19 10:02
 */

@RequestMapping("/order")
@RestController
public class OrderController {

    @Resource
    private RestTemplate restTemplate;

    private LoadBalance loadBalance = new RandomLoadBalance();

    @RequestMapping("/get/{id}")
    public Object getOrder(HttpServletRequest request, @PathVariable("id") String id){
        //随机获取host
        String host = loadBalance.chooseServiceHost();
        Product product = restTemplate.getForObject("http://" + host + "/product/get/1", Product.class);
        return new Order(id,"ordername",product);

    }
}

复制代码

发起多次请求,会发现随机调用其中一个服务

Watcher机制

删除List中一个服务的信息

代码地址:git

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