Zookeeper是一个高性能的分布式应用协调服务的框架。Zookeeper=Zoo+keeper,中文直译是动物园的看守者。
是Google的Chubby一个开源的实现,它是集群的管理者,监视着集群中各个节点的状态根据节点提交的反馈进行下一步合理操作。最终,将简单易用的接口和性能高效、功能稳定的系统提供给用户
Zookeeper可以用于解决很多分布式系统遇到的问题,比如分布式锁,分布式协调,分布式消息队列等。
在官网下载最新的Zookeeper稳定版,http://zookeeper.apache.org/releases.html#download,将下载的文件存放在本地目录及安装完毕,本文将Zookeeper安装在/Developer/java/project目录。本文下载的是zookeeper-3.4.9版本。
下载完之后,将conf目录下的zoo_sample.cfg文件重命名成zoo.cfg文件。这个文件存放着Zookeeper的所有配置信息。
tickTime=2000
initLimit=10
syncLimit=5
dataDir=/tmp/zookeeper
clientPort=2181
maxClientCnxns=60
autopurge.snapRetainCount=3
autopurge.purgeInterval=1
通过zkServer.sh start命令启动Zookeeper,启动后默认端口是2181,启动成功后命令行会回显已经启动成功的标示STARTED。
tengfeifangtf:bin tengfei.fangtf$ sh /Developer/java/project/zookeeper-3.4.9/bin/zkServer.sh start
ZooKeeper JMX enabled by default
Using config: /Developer/java/project/zookeeper-3.4.9/bin/../conf/zoo.cfg
-n Starting zookeeper ...
STARTED
通过如下命令连接Zookeeper服务器端。如果服务器端不存在,则会抛出java.net.ConnectException: Connection refused异常
tengfeifangtf:bin tengfei.fangtf$ sh /Developer/java/project/zookeeper-3.4.9/bin/zkCli.sh -server 127.0.0.1:2181
Connecting to 127.0.0.1:2181
2016-09-17 22:02:00,703 [myid:] - INFO [main:Environment@100] - Client environment:zookeeper.version=3.4.9-1757313, built on 08/23/2016 06:50 GMT
2016-09-17 22:02:00,707 [myid:] - INFO [main:Environment@100] - Client environment:host.name=192.168.100.224
2016-09-17 22:02:00,707 [myid:] - INFO [main:Environment@100] - Client environment:java.version=1.6.0_65
2016-09-17 22:02:00,710 [myid:] - INFO [main:Environment@100] - Client environment:java.vendor=Apple Inc.
2016-09-17 22:02:00,710 [myid:] - INFO [main:Environment@100] - Client environment:java.home=/Library/Java/JavaVirtualMachines/1.6.0.jdk/Contents/Home
2016-09-17 22:02:00,710 [myid:] - INFO [main:Environment@100] - Client environment:java.class.path=/Developer/java/project/zookeeper-3.4.9/bin/../build/classes:/Developer/java/project/zookeeper-3.4.9/bin/../build/lib/*.jar:/Developer/java/project/zookeeper-3.4.9/bin/../lib/slf4j-log4j12-1.6.1.jar:/Developer/java/project/zookeeper-3.4.9/bin/../lib/slf4j-api-1.6.1.jar:/Developer/java/project/zookeeper-3.4.9/bin/../lib/netty-3.10.5.Final.jar:/Developer/java/project/zookeeper-3.4.9/bin/../lib/log4j-1.2.16.jar:/Developer/java/project/zookeeper-3.4.9/bin/../lib/jline-0.9.94.jar:/Developer/java/project/zookeeper-3.4.9/bin/../zookeeper-3.4.9.jar:/Developer/java/project/zookeeper-3.4.9/bin/../src/java/lib/*.jar:/Developer/java/project/zookeeper-3.4.9/bin/../conf:
2016-09-17 22:02:00,711 [myid:] - INFO [main:Environment@100] - Client environment:java.library.path=.:/Library/Java/Extensions:/System/Library/Java/Extensions:/usr/lib/java
2016-09-17 22:02:00,711 [myid:] - INFO [main:Environment@100] - Client environment:java.io.tmpdir=/var/folders/6s/z6xt4ypn387239k7q1ty_rkc0000gn/T/
2016-09-17 22:02:00,713 [myid:] - INFO [main:Environment@100] - Client environment:java.compiler=<NA>
2016-09-17 22:02:00,713 [myid:] - INFO [main:Environment@100] - Client environment:os.name=Mac OS X
2016-09-17 22:02:00,714 [myid:] - INFO [main:Environment@100] - Client environment:os.arch=x86_64
2016-09-17 22:02:00,714 [myid:] - INFO [main:Environment@100] - Client environment:os.version=10.11.6
2016-09-17 22:02:00,714 [myid:] - INFO [main:Environment@100] - Client environment:user.name=tengfei.fangtf
2016-09-17 22:02:00,714 [myid:] - INFO [main:Environment@100] - Client environment:user.home=/Users/tengfei
2016-09-17 22:02:00,714 [myid:] - INFO [main:Environment@100] - Client environment:user.dir=/Developer/java/project/zookeeper-3.4.9/bin
2016-09-17 22:02:00,716 [myid:] - INFO [main:ZooKeeper@438] - Initiating client connection, connectString=127.0.0.1:2181 sessionTimeout=30000 watcher=org.apache.zookeeper.ZooKeeperMain$MyWatcher@3a21b220
Welcome to ZooKeeper!
2016-09-17 22:02:00,754 [myid:] - INFO [main-SendThread(127.0.0.1:2181):ClientCnxn$SendThread@1032] - Opening socket connection to server 127.0.0.1/127.0.0.1:2181. Will not attempt to authenticate using SASL (java.lang.SecurityException: Unable to locate a login configuration)
JLine support is enabled
2016-09-17 22:02:00,775 [myid:] - INFO [main-SendThread(127.0.0.1:2181):ClientCnxn$SendThread@876] - Socket connection established to 127.0.0.1/127.0.0.1:2181, initiating session
[zk: 127.0.0.1:2181(CONNECTING) 0] 2016-09-17 22:02:01,075 [myid:] - INFO [main-SendThread(127.0.0.1:2181):ClientCnxn$SendThread@1299] - Session establishment complete on server 127.0.0.1/127.0.0.1:2181, sessionid = 0x157386e843d0004, negotiated timeout = 30000
WATCHER::
WatchedEvent state:SyncConnected type:None path:null
连接成功后会进入Zookeeper交互式窗口,命令行左边显示如下,然后你就可以使用Zookeeper提供的命令来创建,修改和删除节点。
[zk: 127.0.0.1:2181(CONNECTED) 0]
使用create参数创建节点,第一个参数是节点路径,第二个参数是节点的数据。
[zk: 127.0.0.1:2181(CONNECTED) 1] create /dmcNode data
Created /dmcNode
注意:节点路径是大小写敏感的。
使用get命令查询节点的数据,会显示节点的数据长度,数据的版本
[zk: 127.0.0.1:2181(CONNECTED) 2] get /dmcNode
data
cZxid = 0x54
ctime = Sat Sep 17 22:07:49 CST 2016
mZxid = 0x54
mtime = Sat Sep 17 22:07:49 CST 2016
pZxid = 0x54
cversion = 0
dataVersion = 0
aclVersion = 0
ephemeralOwner = 0x0
dataLength = 4
numChildren = 0
通过get命令我们可以看到Zookeeper节点的数据结构
这些属性可以参考《Zookeeper官方文档》Zookeeper tatStructure章节https://zookeeper.apache.org/doc/r3.4.6/zookeeperProgrammers.html#sc_zkStatStructure
可以发现dataVersion从刚才的0变成了1,数据长度也变化了。
[zk: 127.0.0.1:2181(CONNECTED) 3] set /dmcNode data1
cZxid = 0x54
ctime = Sat Sep 17 22:07:49 CST 2016
mZxid = 0x55
mtime = Sat Sep 17 22:10:46 CST 2016
pZxid = 0x54
cversion = 0
dataVersion = 1
aclVersion = 0
ephemeralOwner = 0x0
dataLength = 5
numChildren = 0
通过delete [path]命令删除节点
[zk: 127.0.0.1:2181(CONNECTED) 12] delete /dmcNode
我们通过help命令可以看下Zookeeper提供哪些操作命令。
[zk: 127.0.0.1:2181(CONNECTED) 0] help
ZooKeeper -server host:port cmd args
connect host:port
get path [watch]
ls path [watch]
set path data [version]
rmr path
delquota [-n|-b] path
quit
printwatches on|off
create [-s] [-e] path data acl
stat path [watch]
close
ls2 path [watch]
history
listquota path
setAcl path acl
getAcl path
sync path
redo cmdno
addauth scheme auth
delete path [version]
setquota -n|-b val path
如果先关闭了Zookeeper服务端,而客户端没有关闭,则客户端会不断的重连服务器端,并抛出异常closing socket connection and attempting reconnect。
sh /Developer/java/project/zookeeper-3.4.9/bin/zkServer.sh stop
<dependency>
<groupId>org.apache.zookeeper</groupId>
<artifactId>zookeeper</artifactId>
<version>3.4.7</version>
</dependency>
演示了ZooKeeper节点的创建,修改和删除操作。
import java.io.IOException;
import org.apache.zookeeper.CreateMode;
import org.apache.zookeeper.KeeperException;
import org.apache.zookeeper.ZooDefs;
import org.apache.zookeeper.ZooKeeper;
/**
*
* @author tengfei.fangtf
* @version $Id: TestZookeeper.java, v 0.1 Sep 14, 2016 5:05:07 PM tengfei.fangtf Exp $
*/
public class TestZookeeper {
public static void main(String[] args) throws IOException, InterruptedException,
KeeperException {
//创建ZooKeeper实例
ZooKeeper zk = new ZooKeeper("127.0.0.1:2181", 100, null);
String path = "/dmc";
//创建一个节点,模式是PERSISTENT
zk.create(path, "1".getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);
System.out.println("创建节点" + path + ",数据为:" + new String(zk.getData(path, null, null)));
//修改节点数据
zk.setData(path, "2".getBytes(), -1);
System.out.println("修改节点" + path + ",数据为:" + new String(zk.getData(path, null, null)));
//删除一个节点
System.out.println(zk.exists(path, null));
zk.delete(path, -1);
//节点是否存在
System.out.println(zk.exists(path, null));
}
}
输出的结果如下:
创建节点/dmc,数据为:1
修改节点/dmc,数据为:2
78,79,1474120607561,1474120607575,1,0,0,0,1,0,78
null