Zookeeper3-实战
引入
ZooKeeper是做分布式协调的，那它协调啥？
配置写在哪里？难道运维人员要登录到每一台机器一台一台地改吗？
可以将配置文件放在一个共享的位置中，比如redis，比如数据库，比如zk，任何一个地方。
zk具有回调机制，就不需要轮询了。
使用ZooKeeper实现分布式配置中心
思路：我们将所有的配置数据用data配置到zk中去，在客户端我们既可以get它，也可以watch它。
一旦外界对这个数据进行了修改，这个修改就会引发watch的回调。
分布式配置中心
代码
测试程序
package com.msb.zookeeper.config;
import org.apache.zookeeper.AsyncCallback;
import org.apache.zookeeper.WatchedEvent;
import org.apache.zookeeper.Watcher;
import org.apache.zookeeper.ZooKeeper;
import org.apache.zookeeper.data.Stat;
import java.util.concurrent.CountDownLatch;
public class WatchCallBack implements Watcher, AsyncCallback.StatCallback, AsyncCallback.DataCallback {
ZooKeeper zk;
MyConf conf;
CountDownLatch cc = new CountDownLatch(1);
public MyConf getConf() {
return conf;
}
public void setConf(MyConf conf) {
this.conf = conf;
}
public ZooKeeper getZk() {
return zk;
}
public void setZk(ZooKeeper zk) {
this.zk = zk;
}
public void aWait() {
//实际是/testLock/AppConf
zk.exists("/AppConf", this, this, "ABC");
try {
cc.await();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
@Override
//DataCallback
public void processResult(int rc, String path, Object ctx, byte[] data, Stat stat) {
if (data != null) {
String s = new String(data);
conf.setConf(s);
cc.countDown();
}
}
@Override
//StatCallback
public void processResult(int rc, String path, Object ctx, Stat stat) {
if (stat != null) {
zk.getData("/AppConf", this, this, "sdfs");
}
}
@Override
public void process(WatchedEvent event) {
switch (event.getType()) {
case None:
break;
case NodeCreated:
zk.getData("/AppConf", this, this, "sdfs");
break;
case NodeDeleted:
//容忍性
//节点被删除事件，这要根据业务的容忍性，写处理方式
System.out.println("节点被删除了");
conf.setConf("");
cc = new CountDownLatch(1);
break;
case NodeDataChanged:
//数据被更改
zk.getData("/AppConf", this, this, "sdfs");
break;
case NodeChildrenChanged:
break;
}
}
}
ZKUtils.java 用来配置Zookeeper的Server端服务器地址，以及创建并返回Zookeeper实例
package com.msb.zookeeper.config;
import org.apache.zookeeper.ZooKeeper;
import java.util.concurrent.CountDownLatch;
public class ZKUtils {
private static ZooKeeper zk;
///testLock 是指定的根目录，后续所有的操作都在以 /testLock 为根目录的基础上进行
private static String address = "192.168.10.71:2181,192.168.10.72:2181,192.168.10.73:2181,192.168.10.74:2181/testLock";
private static DefaultWatch watch = new DefaultWatch();
private static CountDownLatch init = new CountDownLatch(1);
public static ZooKeeper getZK(){
try {
zk = new ZooKeeper(address,1000,watch);
watch.setCc(init);
init.await();
} catch (Exception e) {
e.printStackTrace();
}
return zk;
}
}
DefaultWatch.java，连接默认watch
package com.msb.zookeeper.config;
import org.apache.zookeeper.WatchedEvent;
import org.apache.zookeeper.Watcher;
import java.util.concurrent.CountDownLatch;
public class DefaultWatch implements Watcher {
CountDownLatch cc ;
public void setCc(CountDownLatch cc) {
this.cc = cc;
}
@Override
public void process(WatchedEvent event) {
System.out.println(event.toString());
switch (event.getState()) {
case Unknown:
break;
case Disconnected:
break;
case NoSyncConnected:
break;
case SyncConnected:
System.out.println("连接成功.");
cc.countDown();
break;
case AuthFailed:
break;
case ConnectedReadOnly:
break;
case SaslAuthenticated:
break;
case Expired:
break;
}
}
}
WatchCallBack.java
package com.msb.zookeeper.config;
import org.apache.zookeeper.AsyncCallback;
import org.apache.zookeeper.WatchedEvent;
import org.apache.zookeeper.Watcher;
import org.apache.zookeeper.ZooKeeper;
import org.apache.zookeeper.data.Stat;
import java.util.concurrent.CountDownLatch;
public class WatchCallBack implements Watcher, AsyncCallback.StatCallback, AsyncCallback.DataCallback {
ZooKeeper zk;
MyConf conf;
CountDownLatch cc = new CountDownLatch(1);
public MyConf getConf() {
return conf;
}
public void setConf(MyConf conf) {
this.conf = conf;
}
public ZooKeeper getZk() {
return zk;
}
public void setZk(ZooKeeper zk) {
this.zk = zk;
}
public void aWait() {
//实际是/testLock/AppConf
zk.exists("/AppConf", this, this, "ABC");
try {
cc.await();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
@Override
//DataCallback
public void processResult(int rc, String path, Object ctx, byte[] data, Stat stat) {
if (data != null) {
String s = new String(data);
conf.setConf(s);
cc.countDown();
}
}
@Override
//StatCallback
public void processResult(int rc, String path, Object ctx, Stat stat) {
if (stat != null) {
zk.getData("/AppConf", this, this, "sdfs");
}
}
@Override
public void process(WatchedEvent event) {
switch (event.getType()) {
case None:
break;
case NodeCreated:
zk.getData("/AppConf", this, this, "sdfs");
break;
case NodeDeleted:
//容忍性
//节点被删除事件，这要根据业务的容忍性，写处理方式
System.out.println("节点被删除了");
conf.setConf("");
cc = new CountDownLatch(1);
break;
case NodeDataChanged:
//数据被更改
zk.getData("/AppConf", this, this, "sdfs");
break;
case NodeChildrenChanged:
break;
}
}
}
zk操作
结果
2021-09-12 18:03:17,296 [myid:] - INFO [main:Environment@98] - Client environment:java.compiler=<NA>
2021-09-12 18:03:17,296 [myid:] - INFO [main:Environment@98] - Client environment:os.name=Windows 7
2021-09-12 18:03:17,296 [myid:] - INFO [main:Environment@98] - Client environment:os.memory.free=109MB
2021-09-12 18:03:17,297 [myid:] - INFO [main:Environment@98] - Client environment:os.memory.max=1808MB
2021-09-12 18:03:17,297 [myid:] - INFO [main:Environment@98] - Client environment:os.memory.total=123MB
2021-09-12 18:03:17,305 [myid:] - INFO [main:ZooKeeper@637] - Initiating client connection, connectString=192.168.10.71:2181,192.168.10.72:2181,192.168.10.73:2181,192.168.10.74:2181/testLock sessionTimeout=1000 watcher=com.msb.zookeeper.config.DefaultWatch@6f79caec
2021-09-12 18:03:17,311 [myid:] - INFO [main:X509Util@77] - Setting -D jdk.tls.rejectClientInitiatedRenegotiation=true to disable client-initiated TLS renegotiation
2021-09-12 18:03:17,489 [myid:] - INFO [main:ClientCnxnSocket@239] - jute.maxbuffer value is 1048575 Bytes
2021-09-12 18:03:17,507 [myid:] - INFO [main:ClientCnxn@1726] - zookeeper.request.timeout value is 0. feature enabled=false
2021-09-12 18:03:37,841 [myid:192.168.10.72:2181] - INFO [main-SendThread(192.168.10.72:2181):ClientCnxn$SendThread@1171] - Opening socket connection to server 192.168.10.72/192.168.10.72:2181.
2021-09-12 18:03:37,842 [myid:192.168.10.72:2181] - INFO [main-SendThread(192.168.10.72:2181):ClientCnxn$SendThread@1173] - SASL config status: Will not attempt to authenticate using SASL (unknown error)
2021-09-12 18:03:37,845 [myid:192.168.10.72:2181] - INFO [main-SendThread(192.168.10.72:2181):ClientCnxn$SendThread@1005] - Socket connection established, initiating session, client: /192.168.10.1:1936, server: 192.168.10.72/192.168.10.72:2181
2021-09-12 18:03:37,864 [myid:192.168.10.72:2181] - INFO [main-SendThread(192.168.10.72:2181):ClientCnxn$SendThread@1438] - Session establishment complete on server 192.168.10.72/192.168.10.72:2181, session id = 0x200010e98900004, negotiated timeout = 4000
WatchedEvent state:SyncConnected type:None path:null
连接成功.
old
old
new
new
节点被删除了
conf diu le ......
分布式锁
测试程序
package com.msb.zookeeper.lock;
import com.msb.zookeeper.config.ZKUtils;
import org.apache.zookeeper.ZooKeeper;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;
public class TestLock {
ZooKeeper zk ;
@Before
public void conn (){
zk = ZKUtils.getZK();
}
@After
public void close (){
try {
zk.close();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
@Test
public void lock(){
for (int i = 0; i < 10; i++) {//模拟10个线程分布在10台机器上
new Thread(){
@Override
public void run() {
WatchCallBack watchCallBack = new WatchCallBack();
watchCallBack.setZk(zk);
String threadName = Thread.currentThread().getName();
watchCallBack.setThreadName(threadName);
//每一个线程：
//抢锁
watchCallBack.tryLock();
//干活
System.out.println(threadName+" working...");
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
//释放锁
watchCallBack.unLock();
}
}.start();
}
while(true){
}
}
}
WatchCallBack.java，分布式锁的Watcher
package com.msb.zookeeper.lock;
import org.apache.zookeeper.*;
import org.apache.zookeeper.data.Stat;
import java.util.Collections;
import java.util.List;
import java.util.concurrent.CountDownLatch;
public class WatchCallBack implements Watcher, AsyncCallback.StringCallback ,AsyncCallback.Children2Callback ,AsyncCallback.StatCallback {
ZooKeeper zk ;
String threadName;
CountDownLatch cc = new CountDownLatch(1);
String pathName;
public String getPathName() {
return pathName;
}
public void setPathName(String pathName) {
this.pathName = pathName;
}
public String getThreadName() {
return threadName;
}
public void setThreadName(String threadName) {
this.threadName = threadName;
}
public ZooKeeper getZk() {
return zk;
}
public void setZk(ZooKeeper zk) {
this.zk = zk;
}
public void tryLock(){
try {
System.out.println(threadName + " create....");
// if(zk.getData("/"))
zk.create("/lock",threadName.getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL_SEQUENTIAL,this,"abc");
cc.await();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
public void unLock(){
try {
zk.delete(pathName,-1);
System.out.println(threadName + " over work....");
} catch (InterruptedException e) {
e.printStackTrace();
} catch (KeeperException e) {
e.printStackTrace();
}
}
@Override
public void process(WatchedEvent event) {
//如果第一个哥们，那个锁释放了，其实只有第二个收到了回调事件！！
//如果，不是第一个哥们，某一个，挂了，也能造成他后边的收到这个通知，从而让他后边那个跟去watch挂掉这个哥们前边的。。。
switch (event.getType()) {
case None:
break;
case NodeCreated:
break;
case NodeDeleted:
zk.getChildren("/",false,this ,"sdf");
break;
case NodeDataChanged:
break;
case NodeChildrenChanged:
break;
}
}
@Override
public void processResult(int rc, String path, Object ctx, String name) {
if(name != null ){
System.out.println(threadName +" create node : " + name );
pathName = name ;
zk.getChildren("/",false,this ,"sdf");
}
}
//getChildren call back
@Override
public void processResult(int rc, String path, Object ctx, List<String> children, Stat stat) {
// System.out.println(threadName+"look locks.....");
// for (String child : children) {
// System.out.println(child);
// }
//一定能看到自己前边的 list children乱序 查询自己位置
Collections.sort(children);
int i = children.indexOf(pathName.substring(1));
//是不是第一个
if(i == 0){
//yes
System.out.println(threadName +" i am first....");
try {
zk.setData("/",threadName.getBytes(),-1);
cc.countDown();
} catch (KeeperException e) {
e.printStackTrace();
} catch (InterruptedException e) {
e.printStackTrace();
}
}else{
//no watch前一个
zk.exists("/"+children.get(i-1),this,this,"sdf");
}
}
@Override
public void processResult(int rc, String path, Object ctx, Stat stat) {
//偷懒
}
}
connectString=192.168.10.71:2181,192.168.10.72:2181,192.168.10.73:2181,192.168.10.74:2181/testLock sessionTimeout=1000 watcher=com.msb.zookeeper.config.DefaultWatch@6f79caec
2021-09-12 19:25:59,328 [myid:] - INFO [main:X509Util@77] - Setting -D jdk.tls.rejectClientInitiatedRenegotiation=true to disable client-initiated TLS renegotiation
2021-09-12 19:25:59,562 [myid:] - INFO [main:ClientCnxnSocket@239] - jute.maxbuffer value is 1048575 Bytes
2021-09-12 19:25:59,576 [myid:] - INFO [main:ClientCnxn@1726] - zookeeper.request.timeout value is 0. feature enabled=false
2021-09-12 19:26:19,929 [myid:192.168.10.73:2181] - INFO [main-SendThread(192.168.10.73:2181):ClientCnxn$SendThread@1171] - Opening socket connection to server 192.168.10.73/192.168.10.73:2181.
2021-09-12 19:26:19,929 [myid:192.168.10.73:2181] - INFO [main-SendThread(192.168.10.73:2181):ClientCnxn$SendThread@1173] - SASL config status: Will not attempt to authenticate using SASL (unknown error)
2021-09-12 19:26:20,181 [myid:192.168.10.73:2181] - WARN [main-SendThread(192.168.10.73:2181):ClientCnxn$SendThread@1247] - Client session timed out, have not heard from server in 20599ms for session id 0x0
2021-09-12 19:26:20,182 [myid:192.168.10.73:2181] - WARN [main-SendThread(192.168.10.73:2181):ClientCnxn$SendThread@1290] - Session 0x0 for sever 192.168.10.73/192.168.10.73:2181, Closing socket connection. Attempting reconnect except it is a SessionExpiredException.
org.apache.zookeeper.ClientCnxn$SessionTimeoutException: Client session timed out, have not heard from server in 20599ms for session id 0x0
at org.apache.zookeeper.ClientCnxn$SendThread.run(ClientCnxn.java:1248)
2021-09-12 19:26:40,606 [myid:192.168.10.72:2181] - INFO [main-SendThread(192.168.10.72:2181):ClientCnxn$SendThread@1171] - Opening socket connection to server 192.168.10.72/192.168.10.72:2181.
2021-09-12 19:26:40,606 [myid:192.168.10.72:2181] - INFO [main-SendThread(192.168.10.72:2181):ClientCnxn$SendThread@1173] - SASL config status: Will not attempt to authenticate using SASL (unknown error)
2021-09-12 19:26:40,611 [myid:192.168.10.72:2181] - INFO [main-SendThread(192.168.10.72:2181):ClientCnxn$SendThread@1005] - Socket connection established, initiating session, client: /192.168.10.1:2467, server: 192.168.10.72/192.168.10.72:2181
2021-09-12 19:26:40,627 [myid:192.168.10.72:2181] - INFO [main-SendThread(192.168.10.72:2181):ClientCnxn$SendThread@1438] - Session establishment complete on server 192.168.10.72/192.168.10.72:2181, session id = 0x200010e98900005, negotiated timeout = 4000
WatchedEvent state:SyncConnected type:None path:null
连接成功.
Thread-3 create....
Thread-2 create....
Thread-9 create....
Thread-4 create....
Thread-6 create....
Thread-0 create....
Thread-1 create....
Thread-5 create....
Thread-8 create....
Thread-7 create....
Thread-3 create node : /lock0000000001
Thread-0 create node : /lock0000000002
Thread-8 create node : /lock0000000003
Thread-1 create node : /lock0000000004
Thread-5 create node : /lock0000000005
Thread-6 create node : /lock0000000006
Thread-2 create node : /lock0000000007
Thread-7 create node : /lock0000000008
Thread-9 create node : /lock0000000009
Thread-4 create node : /lock0000000010
Thread-3 i am first....
Thread-3 working...
Thread-3 over work....
Thread-0 i am first....
Thread-0 working...
Thread-0 over work....
Thread-8 i am first....
Thread-8 working...
Thread-8 over work....
Thread-1 i am first....
Thread-1 working...
Thread-1 over work....
Thread-5 i am first....
Thread-5 working...
Thread-5 over work....
Thread-6 i am first....
Thread-6 working...
Thread-6 over work....
Thread-2 i am first....
Thread-2 working...
Thread-2 over work....
Thread-7 i am first....
Thread-7 working...
Thread-7 over work....
Thread-9 i am first....
Thread-9 working...
Thread-9 over work....
Thread-4 i am first....
Thread-4 working...
Thread-4 over work....
在程序执行的同时，从Zookeeper的Client端不断获取目录内容，看到整个过程大致是这样的：
当一个线程中的任务执行完之后，显示调用了zk.delete(pathName, -1)将节点删除。这样就能触发下一个正在watch它的节点所在的线程，去判断自己是不是在排名的第一个。
如果是第一个，开始干活
如果不是第一个，watch它的前一个（这种情况出现在前一个节点突然挂了的情况）
本文来自博客园，作者：gary2048，转载请注明原文链接：https://www.cnblogs.com/zhoum/p/15259645.html
本文版权归作者和博客园共有，欢迎转载，但未经作者同意必须保留此段声明，且在文章页面明显位置给出原文连接，否则保留追究法律责任的权利。
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