簡介

當兩個進程在執行任務的時候，A調用了B，A需要等待B完成以後的通知，我們可以使用curator的屏障功能來實現。

官方文檔：http://curator.apache.org/curator-recipes/barrier.html

JavaDoc：http://curator.apache.org/apidocs/org/apache/curator/framework/recipes/barriers/DistributedBarrier.html

代碼示例

import org.apache.curator.framework.CuratorFramework;
import org.apache.curator.framework.CuratorFrameworkFactory;
 
import org.apache.curator.framework.recipes.barriers.DistributedBarrier;
import org.apache.curator.retry.ExponentialBackoffRetry;

public class Barrier {
    private static CuratorFramework client = CuratorFrameworkFactory.newClient("localhost:2181", new ExponentialBackoffRetry(3000, 3));
    private
 
 static String path = "/barrier/001";
    public static void main(String[] args) throws Exception {
        client.start();
        DistributedBarrier barrier = new DistributedBarrier(client, path);
        barrier.setBarrier();
        System.out.println("set barrier");
        notifyTo();
        System.out.println(
 
"wait barrier");
        barrier.waitOnBarrier();
        System.out.println("wait end");
        client.close();
    }

    public static void notifyTo() {
        new Thread(() -> {
            DistributedBarrier barrier = new DistributedBarrier(client, path);
            try {
                System.out.println("notify sleep...");
                Thread.sleep(3000);
                barrier.removeBarrier();
                System.out.println("notify remove barrier");
            } catch (Exception e) {
                e.printStackTrace();
            }
        }).start();
    }
}

輸出結果

set barrier
wait barrier
notify sleep...
notify remove barrier
wait end

主線程等待屏障被移除了以後繼續執行

六、curator recipes之屏障barrier