简介

Curator是Netflix公司开源的一个Zookeeper客户端，与Zookeeper提供的原生客户端相比，Curator的抽象层次更高，简化了Zookeeper客户端的开发量。

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安装部署

1：安装jdk,这个就不说了，都知道怎么安装

2：到apache官网下载zookeeper

#wget http://mirror.bit.edu.cn/apache/zookeeper/zookeeper-3.4.10/zookeeper-3.4.10.tar.gz
#tar zxvf zookeeper-3.4.6.tar.gz
#cd zookeeper-3.4.6
#cp conf/zoo_sample.cfg conf/zoo.cfg
#./bin/zkServer.sh start

这样zookeeper就搞定了，现在我们通过客户端练上去看看状态

#./bin/zkCli.sh

[zk: localhost:2181(CONNECTED) 0] help
ZooKeeper -server host:port cmd args
 stat path [watch]
 set path data [version]
 ls path [watch]
 delquota [-n|-b] path
 ls2 path [watch]
 setAcl path acl
 setquota -n|-b val path
 history 
 redo cmdno
 printwatches on|off
 delete path [version]
 sync path
 listquota path
 rmr path
 get path [watch]
 create [-s] [-e] path data acl
 addauth scheme auth
 quit 
 getAcl path
 close 
 connect host:port

我们简单测试几个常用的命令：

• ls

查看路径下所有节点

[zk: localhost:2181(CONNECTED) 2] ls /
[zk55, zookeeper]

• create

用来创建路径节点

[zk: localhost:2181(CONNECTED) 5] create /zk123 mydata
Created /zk123
[zk: localhost:2181(CONNECTED) 6] ls /
[zk55,zk123, zookeeper]

• get

获取节点值

[zk: localhost:2181(CONNECTED) 8] get /zk123 
mydata
cZxid = 0x29
ctime = Thu Dec 28 16:24:07 CST 2017
mZxid = 0x29
mtime = Thu Dec 28 16:24:07 CST 2017
pZxid = 0x29
cversion = 0
dataVersion = 0
aclVersion = 0
ephemeralOwner = 0x0
dataLength = 6
numChildren = 0

• set

设置节点值

[zk: localhost:2181(CONNECTED) 9] set /zk123 hello
cZxid = 0x29
ctime = Thu Dec 28 16:24:07 CST 2017
mZxid = 0x2a
mtime = Thu Dec 28 16:26:08 CST 2017
pZxid = 0x29
cversion = 0
dataVersion = 1
aclVersion = 0
ephemeralOwner = 0x0
dataLength = 5
numChildren = 0
[zk: localhost:2181(CONNECTED) 10] get /zk123 
hello
cZxid = 0x29
ctime = Thu Dec 28 16:24:07 CST 2017
mZxid = 0x2a
mtime = Thu Dec 28 16:26:08 CST 2017
pZxid = 0x29
cversion = 0
dataVersion = 1
aclVersion = 0
ephemeralOwner = 0x0
dataLength = 5
numChildren = 0

• delete

删除节点

zk: localhost:2181(CONNECTED) 11] delete /zk123
[zk: localhost:2181(CONNECTED) 12] ls /
[zk55, zookeeper]

curator连接Zookeeper

先说一下版本的问题吧，官网给的说明是：

While ZooKeeper 3.5.x is still considered "beta" by the ZooKeeper development team, the reality is that it is used in production by many users. However, ZooKeeper 3.4.x is also used in production. Prior to Apache Curator 4.0, both versions of ZooKeeper were supported via two versions of Apache Curator. Starting with Curator 4.0 both versions of ZooKeeper are supported via the same Curator libraries.

Curator 4.0 supports ZooKeeper 3.4.x ensembles in a soft-compatibility mode. To use this mode you must exclude ZooKeeper when adding Curator to your dependency management tool.

Maven

<dependency>
    <groupId>org.apache.curator</groupId>
    <artifactId>curator-recipes</artifactId>
    <version>${curator-version}</version>
    <exclusions>
        <exclusion>
            <groupId>org.apache.zookeeper</groupId>
            <artifactId>zookeeper</artifactId>
        </exclusion>
    </exclusions>
</dependency>

这里我maven的配置如下：

<dependency>
    <groupId>org.apache.zookeeper</groupId>
    <artifactId>zookeeper</artifactId>
    <version>3.4.10</version>
</dependency>
<dependency>
    <groupId>org.apache.curator</groupId>
    <artifactId>curator-recipes</artifactId>
    <version>4.0.0</version>
    <exclusions>
        <exclusion>
            <groupId>org.apache.zookeeper</groupId>
            <artifactId>zookeeper</artifactId>
        </exclusion>
    </exclusions>
</dependency>

官方给的样例中提供了两种连接方式如下：

public static CuratorFramework createSimple(String connectionString)
{
    // these are reasonable arguments for the ExponentialBackoffRetry. The first
    // retry will wait 1 second - the second will wait up to 2 seconds - the
    // third will wait up to 4 seconds.
    ExponentialBackoffRetry retryPolicy = new ExponentialBackoffRetry(1000, 3);

    // The simplest way to get a CuratorFramework instance. This will use default values.
    // The only required arguments are the connection string and the retry policy
    return CuratorFrameworkFactory.newClient(connectionString, retryPolicy);
}

public static CuratorFramework  createWithOptions(String connectionString, RetryPolicy retryPolicy, int connectionTimeoutMs, int sessionTimeoutMs)
{
    // using the CuratorFrameworkFactory.builder() gives fine grained control
    // over creation options. See the CuratorFrameworkFactory.Builder javadoc
    // details
    return CuratorFrameworkFactory.builder()
            .connectString(connectionString)
            .retryPolicy(retryPolicy)
            .connectionTimeoutMs(connectionTimeoutMs)
            .sessionTimeoutMs(sessionTimeoutMs)
            // etc. etc.
            .build();
}

我们随便选一种对之前用命令操作的场景模拟一次，核心代码如下：

连接zk:
CuratorFramework client = ClientConnect.createSimple(ZK_ADDRESS);
client.start();

创建节点（create）：
client.create().creatingParentsIfNeeded().forPath(ZK_PATH, data1.getBytes());

查询节点(ls /)：
client.getChildren().forPath("/");

写入数据(set):
client.setData().forPath(ZK_PATH, data2.getBytes());

获取数据(get):
client.getData().forPath(ZK_PATH);

删除节点(delete):
client.delete().forPath(ZK_PATH);

判断节点是否存在：
client.checkExists().forPath(ZK_PATH)

对指到节点监听：
PathChildrenCache watcher = new PathChildrenCache(
        client,
        ZK_PATH,
        true    // if cache data
);
watcher.getListenable().addListener((client1, event) -> {
    ChildData data = event.getData();
    if (data == null) {
        System.out.println("No data in event[" + event + "]");
    } else {
        System.out.println("Receive event: "
                + "type=[" + event.getType() + "]"
                + ", path=[" + data.getPath() + "]"
                + ", data=[" + new String(data.getData()) + "]"
                + ", stat=[" + data.getStat() + "]");}});
watcher.start(PathChildrenCache.StartMode.BUILD_INITIAL_CACHE);
System.out.println("Register zk watcher successfully!");

Thread.sleep(Integer.MAX_VALUE);
这时你就会发现如果有人操作ZK_PATH，就会有日志打印出来