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| import com.google.common.base.Strings;
import com.google.common.util.concurrent.ThreadFactoryBuilder;
import org.apache.zookeeper.*;
import java.io.IOException;
import java.util.concurrent.*;
public class DistributedLockBasedOnZookeeper {
private String hostPort = "host:port";
private String lockNameSpace = "/myLock";
private String nodeString = lockNameSpace + "/test1";
private ZooKeeper zk;
public DistributedLockBasedOnZookeeper(){
try {
zk = new ZooKeeper(hostPort, 6000, event -> {
System.out.println("Receive event " + event);
if (Watcher.Event.KeeperState.SyncConnected == event.getState()){
System.out.println("Connection is established...");
}
});
} catch (IOException e) {
e.printStackTrace();
}
}
private void ensureRootPath() throws InterruptedException {
try {
if (zk.exists(lockNameSpace, true) == null){
zk.create(lockNameSpace, "".getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);
}
} catch (KeeperException e) {
e.printStackTrace();
}
}
private void watchNode(String nodeString, final Thread thread){
try {
zk.exists(nodeString, event -> {
System.out.println("==" + event.toString());
if (event.getType() == Watcher.Event.EventType.NodeDeleted){
System.out.println("There is a Thread released lock.....");
thread.interrupt();
}
try {
zk.exists(nodeString, true);
} catch (KeeperException e) {
e.printStackTrace();
} catch (InterruptedException e) {
e.printStackTrace();
}
});
} catch (KeeperException e) {
e.printStackTrace();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
public boolean getLock() throws InterruptedException {
String path = null;
ensureRootPath();
watchNode(nodeString, Thread.currentThread());
while (true){
try {
path = zk.create(nodeString, "".getBytes(),ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL);
} catch (KeeperException e) {
System.out.println(Thread.currentThread().getName() + "getting Lock but can not get");
Thread.sleep(5000);
}
if (!Strings.nullToEmpty(path).trim().isEmpty()){
System.out.println(Thread.currentThread().getName() + " get Lock...");
return true;
}
}
}
public void unlock(){
try {
zk.delete(nodeString, -1);
System.out.println(Thread.currentThread().getName() + " release Lock...");
} catch (InterruptedException e) {
e.printStackTrace();
} catch (KeeperException e) {
e.printStackTrace();
}
}
public static void main(String[] args) {
ThreadFactory threadFactory = new ThreadFactoryBuilder().setNameFormat("demo-pool-%d").build();
ExecutorService service = new ThreadPoolExecutor(10, 10, 1000L, TimeUnit.MILLISECONDS,
new ArrayBlockingQueue<>(1024), threadFactory, new ThreadPoolExecutor.AbortPolicy());
for (int i = 0; i < 4; i++){
service.execute(() -> {
DistributedLockBasedOnZookeeper lockBasedOnZookeeper = new DistributedLockBasedOnZookeeper();
try {
lockBasedOnZookeeper.getLock();
Thread.sleep(3000);
} catch (InterruptedException e) {
e.printStackTrace();
}
lockBasedOnZookeeper.unlock();
});
}
service.shutdown();
}
}
|