深入浅出zookeeper1

最近想了解一下zookeeper,写个博客做个记录;

什么是zookeeper

ZooKeeper :官网是一个开源的分布式协调服务,原本是Hadoop大数据内部的一个组件,然后现在我们主要就是用来做dubbo的注册中心,当然不止这点作用,还可以 实现诸如数据发布/订阅、负载均衡、命名服务、分布式协调/通知、集群管理、Master 选举、分布式锁和分布式队列等功能。贴一张百度的图:


如何下载

官网里面找到下载,就会跳这里:https://www.apache.org/dyn/closer.cgi/zookeeper/

然后直接下载


两个都下载了,然后解压


一个是有源码的,一个是执行文件,zookeeper也是个maven项目,有空可以研究一下源码,现在只想先了解一下.我们直接进到bin里面执行:zkServer.cmd发现一闪而过.百度一下,发现解决:
进到conf文件将zoo_sample.cfg文件打开看看,也看不懂,修改一下目录,因为是windows的:

参数常用的就几个:
tickTime:就是心跳时间了,心跳机制还是有听说过得
dataDir:就是zookeeper的一些文件保存的目录
clientPort:就是监听的端口了,默认2181就不动了
我就只改个目录好了:

dataDir=E:/zookeeper_study/tmp/zookeeper/data

然后改个名字zoo.cfg,然后启动,就成功了!

使用zkcli简单尝试

bin目录下有zkCli.cmd,要是你zkserver启动成功,那就直接点这个,就会出现一个窗口,

然后随便输入个help:

可以看出大概这些命令,就简单创个节点,修改一下删除好了:

create /aaa bbb
get /aaa
set /aaa ccc
get /aaa
delete /aaa
get /aaa

#创建子节点
create -e /temp/aaa ccc
#查看某个节点的状态
stat /temp
#使用-s参数，创建一个顺序节点，我们虽然指定的节点名是aaa，但是实际上，名称却是 /temp/aa0000000001，如果我们重复执行可以在分布式环境下主键生成器：
create -s /temp/aa

简单的试了试,当然也可以

通过javaapi来进行操作节点

引入pom

   <!-- https://mvnrepository.com/artifact/org.apache.zookeeper/zookeeper -->
        <dependency>
            <groupId>org.apache.zookeeper</groupId>
            <artifactId>zookeeper</artifactId>
            <version>3.5.5</version>
        </dependency>

随便抄个代码https://blog.csdn.net/u010398771/article/details/82420504,他那复制下来有问题,我就删除部分,自己搞了搞能够跑通,不知道为啥连接很慢,算了不管了

import org.apache.zookeeper.*;
import org.apache.zookeeper.Watcher.Event.KeeperState;

import java.util.List;
import java.util.concurrent.CountDownLatch;

public class ZooKeeperProSync implements Watcher {

    private static ZooKeeper zookeeper;

    private static final int SESSION_TIME_OUT = 2000;

    private CountDownLatch countDownLatch = new CountDownLatch(1);

    @Override
    public void process(WatchedEvent event) {
        if (event.getState() == KeeperState.SyncConnected) {
            System.out.println("Watch received event");
            countDownLatch.countDown();
        }
    }

    /**
     * 连接zookeeper
     *     * @param host
     *     * @throws Exception
     *    
     */

    public void connectZookeeper(String host) throws Exception {
        zookeeper = new ZooKeeper(host, SESSION_TIME_OUT, this);
        countDownLatch.await();
        System.out.println("zookeeper connection success");
    }

    /**
     *     * 创建节点
     *     * @param path
     *     * @param data
     *     * @throws Exception
     *    
     */

    public String createNode(String path, String data) throws Exception {
        return this.zookeeper.create(path, data.getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);
    }

    /**
     *     * 获取路径下所有子节点
     *     * @param path
     *     * @return
     *     * @throws KeeperException
     *     * @throws InterruptedException
     *    
     */
    public List<String> getChildren(String path) throws KeeperException, InterruptedException {
        List<String> children = zookeeper.getChildren(path, false);
        return children;
    }

    /**
     *     * 获取节点上面的数据
     *     * @param path  路径
     *     * @return
     *     * @throws KeeperException
     *     * @throws InterruptedException
     *    
     */
    public String getData(String path) throws KeeperException, InterruptedException {
        byte[] data = zookeeper.getData(path, false, null);
        if (data == null) {
            return "";
        }
        return new String(data);
    }
    
    public static void main(String[] args) throws Exception {
    //连接zookeeper并且注册一个默认的监听器
        zookeeper = new ZooKeeper("127.0.0.1:2181", 5000, //
                new ZooKeeperProSync());
        ZooKeeperProSync zooKeeperProSync = new ZooKeeperProSync();
        List<String> children = zooKeeperProSync.getChildren("/");
        for (String child : children) {
            System.out.println(child);
        }
    }

}