Zookeeper之原生連接、數據存儲和事件機制

鑑於前面幾篇博客已經將zookeeper單機和集羣搭建完成，現在我們來了解下如何使用代碼操作zookeeper

本文是建立連接和數據存儲

直接開始乾貨：

首先pom文件引入zookeeper依賴，我裝的版本是3.6.0 大家根據情況來定。

<dependency>
    <groupId>org.apache.zookeeper</groupId>
    <artifactId>zookeeper</artifactId>
    <version>3.6.0</version>
</dependency>

碼來～～～～

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

import java.io.IOException;
import java.util.concurrent.CountDownLatch;

/**
 * @Title: Spring-distributed
 * @Description:
 * @author: liaryank
 * @Date: 2020/5/6 11:28 上午
 * @Version: 1.0
 */
public class ZookeeperClient {

    public static void main(String[] args) {
        try  {
            
            final CountDownLatch countDownLatch = new CountDownLatch(1);
            //這裏綁定zookeeper服務器除了 observe 都要寫上 因爲可能出現任何一臺機器成爲leader 4000是心跳
            ZooKeeper zooKeeper = new ZooKeeper("192.168.3.32:2181," +
                    "192.168.3.33:2181,192.168.3.34:2181", 4000, new Watcher() {
                // watcher 的概念建議請看下面
                @Override
                public void process(WatchedEvent watchedEvent) {
                   if (Event.KeeperState.SyncConnected== watchedEvent.getState()){
                       //如果收到了服務端的響應事件，連接成功
                       countDownLatch.countDown();
                   }
                }
            });
            countDownLatch.await();
            System.out.println(zooKeeper.getState());

            //添加節點  ACL：ZooDefs.Ids.OPEN_ACL_UNSAFE權限控制 open是任何人都可以訪問，PERSISTENT節點類型爲持久化
            zooKeeper.create("/zk-persis-liaryank","0".getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);
            Thread.sleep(1000);
            Stat stat=new Stat();
            //得到當前節點的值 stat是當前節點的值 也就是自己創建的/zk-persis-liaryank的值
            byte[] bytes=zooKeeper.getData("/zk-persis-liaryank",null,stat);
                    System.out.println(new String(bytes));
            //修改節點值 Version這裏是屬於樂觀鎖 
            zooKeeper.setData("/zk-persis-liaryank","1".getBytes(),stat.getVersion());
                    //得到當前節點的值
            byte[] bytes1=zooKeeper.getData("/zk-persis-liaryank",null,stat);
                    System.out.println(new String(bytes1));
            //zooKeeper.delete("/zk-persis-liaryank",stat.getVersion());
            zooKeeper.close();
            if (zooKeeper != null) {
                System.out.println("關閉連接");
                zooKeeper.close();
            }
        } catch (IOException e) {
            e.printStackTrace();
        } catch (InterruptedException | KeeperException e) {
            e.printStackTrace();
        }

    }
}

運行結果

服務器端查看 stat就是下面圖中的數據，都可以獲取到，可以自行打印輸出下

已經將0 改爲了1

再試試刪除

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

import java.io.IOException;
import java.util.concurrent.CountDownLatch;

/**
 * @Title: Spring-distributed
 * @Description:
 * @author: liaryank
 * @Date: 2020/5/6 11:28 上午
 * @Version: 1.0
 */
public class ZookeeperClient {

    public static void main(String[] args) {
        try  {
            final CountDownLatch countDownLatch = new CountDownLatch(1);
            ZooKeeper zooKeeper = new ZooKeeper("192.168.3.32:2181," +
                    "192.168.3.33:2181,192.168.3.34:2181", 4000, new Watcher() {
                @Override
                public void process(WatchedEvent watchedEvent) {
                   if (Event.KeeperState.SyncConnected== watchedEvent.getState()){
                       //如果收到了服務端的響應事件，連接成功
                       countDownLatch.countDown();
                   }
                }
            });
            countDownLatch.await();
            System.out.println(zooKeeper.getState());
            Stat stat=new Stat();
            //得到當前節點的值
            byte[] bytes=zooKeeper.getData("/zk-persis-liaryank",null,stat);
            zooKeeper.delete("/zk-persis-liaryank",stat.getVersion());
            zooKeeper.close();
            if (zooKeeper != null) {
                System.out.println("關閉連接");
                zooKeeper.close();
            }
        } catch (IOException e) {
            e.printStackTrace();
        } catch (InterruptedException | KeeperException e) {
            e.printStackTrace();
        }

    }

運行結果

你可以將刪除直接寫到上邊一起執行一下加點打印輸出就可以看到完整的增刪改查效果了。

ok現在我們來講事件機制

講事件機制前先補充一下watcher

Watcher 監聽機制是 Zookeeper 中非常重要的特性，我們基於 zookeeper 上創建的節點，可以對這些節點綁定監聽事件，比如可以監聽節點數據變更、節點刪除、子節點狀態變更等事件，通過這個事件機制，可以基於 zookeeper 實現分佈式鎖、集羣管理等功能.

watcher 特性:當數據發生變化的時候， zookeeper 會產生一個 watcher 事件，並且會發送到客戶端。但是客戶端只會收到一次通知。如果後續這個節點再次發生變化，那麼之前設置 watcher 的客戶端不會再次收到消息。 (watcher 是一次性的操作)。可以通過循環監聽去達到永久監聽效果.

註冊事件機制: 通過這三個操作來綁定事件 :getData、Exists、getChildren

觸發事件: 凡是事務類型的操作，都會觸發監聽事件。 create /delete /setData

watcher 事件類型

None (-1), 客戶端鏈接狀態發生變化的時候，會收到 none 的事件

NodeCreated (1), 創建節點的事件。比如zk-persis-liaryank時

NodeDeleted (2), 刪除節點事件。
NodeDataChanged (3), 節點數據發生變更時。

NodeChildrenChanged (4); 子節點被創建、被刪除、會發生事件觸發

碼來～～～

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

import java.io.IOException;
import java.util.concurrent.CountDownLatch;

/**
 * @Title: Spring-distributed
 * @Description:
 * @author: liaryank
 * @Date: 2020/5/6 3:19 下午
 * @Version: 1.0
 */
public class WatcherDemo {

    public static void main(String[] args) {
        try  {
            final CountDownLatch countDownLatch = new CountDownLatch(1);
            ZooKeeper zooKeeper = new ZooKeeper("192.168.3.32:2181," +
                    "192.168.3.33:2181,192.168.3.34:2181", 4000, new Watcher() {
                @Override
                public void process(WatchedEvent watchedEvent) {
                    System.out.println("全局默認事件："+watchedEvent.getType());
                    if (Event.KeeperState.SyncConnected== watchedEvent.getState()){
                        //如果收到了服務端的響應事件，連接成功
                        countDownLatch.countDown();
                    }
                }
            });
            countDownLatch.await();
            System.out.println(zooKeeper.getState());

            zooKeeper.create("/zk-persis-liaryank","1".getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE,CreateMode.PERSISTENT);
            //這裏通過exits綁定事件
            Stat stat = zooKeeper.exists("/zk-persis-liaryank", new Watcher() {
                @Override
                public void process(WatchedEvent watchedEvent) {
                    System.out.println(watchedEvent.getType()+"==>"+watchedEvent.getPath());
                    try {
                        //再一次綁定事件，相當於永久註冊監聽 這裏設置的true 是全局的watch
                        zooKeeper.exists(watchedEvent.getPath(),true);
                    } catch (KeeperException e) {
                        e.printStackTrace();
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }
            });
            //修改事務類型的操作來出發監聽事件
            stat=zooKeeper.setData("/zk-persis-liaryank","2".getBytes(),stat.getVersion());
            Thread.sleep(1000);
            //然後刪除
            zooKeeper.delete("/zk-persis-liaryank",stat.getVersion());
            //修改的時候讓該內容進入只讀狀態
            System.in.read();
            zooKeeper.close();
            if (zooKeeper != null) {
                System.out.println("關閉連接");
                zooKeeper.close();
            }
        } catch (IOException e) {
            e.printStackTrace();
        } catch (InterruptedException | KeeperException e) {
            e.printStackTrace();
        }

    }
}

運行結果如下

ok 原生操作到這裏就完事了

Zookeeper之原生連接、數據存儲和事件機制

Soring IOC和DI

JVM 深入簡出(一)

RPC、 SOA概念

分佈式 CAP、BASE理論

nacos安裝配置

Mac下配置sublime實現LaTeX

https://yachay.unat.edu.pe/blog/index.php?comment_area=format_blog&comment_component=blog&comment_co

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