如何在CentOS上利用Zookeeper进行服务发现

在CentOS上利用Zookeeper进行服务发现，可以按照以下步骤进行：

1. 安装Zookeeper

首先，你需要在CentOS上安装Zookeeper。你可以从Apache Zookeeper的官方网站下载最新版本的Zookeeper，并按照官方文档进行安装。

下载并解压Zookeeper

wget https://archive.apache.org/dist/zookeeper/zookeeper-3.7.0/apache-zookeeper-3.7.0-bin.tar.gz
tar -xzf apache-zookeeper-3.7.0-bin.tar.gz
mv apache-zookeeper-3.7.0-bin /opt/zookeeper

配置Zookeeper

编辑Zookeeper的配置文件/opt/zookeeper/conf/zoo.cfg，添加以下内容：

tickTime=2000
dataDir=/var/lib/zookeeper
clientPort=2181
initLimit=5
syncLimit=2
server.1=zoo1:2888:3888
server.2=zoo2:2888:3888
server.3=zoo3:2888:3888

其中，server.1, server.2, server.3是你的Zookeeper集群节点的地址和端口。

启动Zookeeper

在每个节点上启动Zookeeper：

/opt/zookeeper/bin/zkServer.sh start

2. 安装服务发现客户端

你可以使用一些现有的服务发现客户端库，比如Consul、Eureka或者直接使用Zookeeper的Java客户端库。

使用Zookeeper Java客户端库

在你的Java项目中添加Zookeeper客户端依赖：

<dependency>
    <groupId>org.apache.zookeeper</groupId>
    <artifactId>zookeeper</artifactId>
    <version>3.7.0</version>
</dependency>

3. 实现服务注册与发现

服务注册

创建一个服务注册类，将服务信息注册到Zookeeper中：

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

public class ServiceRegistry {
    private static final String ZK_ADDRESS = "zoo1:2181,zoo2:2181,zoo3:2181";
    private static final int SESSION_TIMEOUT = 3000;
    private static final String REGISTRY_PATH = "/services/my-service";

    public void registerService(String serviceName, String serviceAddress) throws Exception {
        ZooKeeper zk = new ZooKeeper(ZK_ADDRESS, SESSION_TIMEOUT, event -> {
            // 处理连接事件
        });

        if (zk.exists(REGISTRY_PATH, false) == null) {
            zk.create(REGISTRY_PATH, new byte[0], ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);
        }

        String servicePath = REGISTRY_PATH + "/" + serviceName;
        if (zk.exists(servicePath, false) == null) {
            zk.create(servicePath, new byte[0], ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);
        }

        String instancePath = servicePath + "/" + serviceAddress;
        zk.create(instancePath, serviceAddress.getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL_SEQUENTIAL);

        zk.close();
    }
}

服务发现

创建一个服务发现类，从Zookeeper中获取服务实例列表：

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

import java.util.ArrayList;
import java.util.List;

public class ServiceDiscovery {
    private static final String ZK_ADDRESS = "zoo1:2181,zoo2:2181,zoo3:2181";
    private static final int SESSION_TIMEOUT = 3000;
    private static final String REGISTRY_PATH = "/services/my-service";

    public List<String> discoverServices() throws Exception {
        ZooKeeper zk = new ZooKeeper(ZK_ADDRESS, SESSION_TIMEOUT, event -> {
            // 处理连接事件
        });

        List<String> instances = new ArrayList<>();
        if (zk.exists(REGISTRY_PATH, false) != null) {
            Stat stat = zk.exists(REGISTRY_PATH, false);
            if (stat != null) {
                byte[] data = zk.getData(REGISTRY_PATH, false, stat);
                String[] services = new String(data).split(",");
                for (String service : services) {
                    Stat instanceStat = zk.exists(REGISTRY_PATH + "/" + service, false);
                    if (instanceStat != null) {
                        byte[] instanceData = zk.getData(REGISTRY_PATH + "/" + service, false, instanceStat);
                        instances.add(new String(instanceData));
                    }
                }
            }
        }

        zk.close();
        return instances;
    }
}

4. 使用服务注册与发现

在你的应用程序中，使用ServiceRegistry类注册服务，并使用ServiceDiscovery类发现服务实例。

注册服务

public class MyService {
    public static void main(String[] args) {
        try {
            ServiceRegistry registry = new ServiceRegistry();
            registry.registerService("my-service", "192.168.1.100:8080");
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

发现服务

public class MyClient {
    public static void main(String[] args) {
        try {
            ServiceDiscovery discovery = new ServiceDiscovery();
            List<String> instances = discovery.discoverServices();
            for (String instance : instances) {
                System.out.println("Found service instance: " + instance);
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

通过以上步骤，你可以在CentOS上利用Zookeeper进行服务发现。