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| package com.will.zk;
import org.apache.zookeeper.*;
import org.apache.zookeeper.data.Stat;
import org.apache.zookeeper.KeeperException.*;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.io.IOException;
import java.nio.charset.StandardCharsets;
import java.util.concurrent.CompletableFuture;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ExecutionException;
public class ZKBarrier<T> implements AsyncCallback.StatCallback {
private static final Logger LOGGER = LoggerFactory.getLogger(ZKBarrier.class);
private final ZooKeeper zk;
private final String path;
private final CompletableFuture<?> future;
private boolean needWatch;
public ZKBarrier(ZooKeeper zk, String path, CompletableFuture<?> future) {
this.zk = zk;
this.path = path;
this.future = future;
this.needWatch = true;
}
public void watchBarrier() {
zk.exists(path, this::process, this, future);
}
private void process(WatchedEvent event) {
LOGGER.info("接收到zk事件回调");
if (needWatch) {
watchBarrier();
}
if (event.getType() == Watcher.Event.EventType.NodeDeleted) {
LOGGER.info("node被删除");
needWatch = false;
}
}
@Override
public void processResult(int rc, String path, Object ctx, Stat stat) {
Code code = Code.get(rc);
if (code == Code.NONODE) {
CompletableFuture<?> future = ctx instanceof CompletableFuture<?> ? (CompletableFuture<?>) ctx: null;
if (future != null) {
future.complete(null);
}
}
}
private static Thread createThread(ZooKeeper zk, String path, CountDownLatch latch) {
Thread t = new Thread(() -> {
CompletableFuture<Integer> future = new CompletableFuture<>();
ZKBarrier<Integer> barrier = new ZKBarrier<>(zk, path, future);
LOGGER.info("watch barrier");
barrier.watchBarrier();
try {
future.get();
} catch (InterruptedException e) {
e.printStackTrace();
Thread.currentThread().interrupt();
} catch (ExecutionException e) {
e.printStackTrace();
}
LOGGER.info("barrier missing, begin to work");
latch.countDown();
});
t.setDaemon(true);
return t;
}
public static void main(String[] args) throws InterruptedException, KeeperException, IOException {
String servers = "localhost:2181";
int timeout = 1000;
String path = "/barriers/barrier-1";
ZooKeeper zk = new ZooKeeper(servers, timeout, event -> {});
ZKOperator zkOperator = new ZKOperator(servers, timeout);
zkOperator.create(path, "".getBytes(StandardCharsets.UTF_8));
CountDownLatch latch = new CountDownLatch(2);
createThread(zk, path, latch).start();
createThread(zk, path, latch).start();
latch.await();
}
}
|