( 转载 )Zookeeper KeeperErrorCode = ConnectionLoss

服务启动时发现报如下错误：

org.apache.zookeeper.KeeperException$ConnectionLossException: KeeperErrorCode = ConnectionLoss

error是在调用zk.exists（）时抛出的。

于是开始google，发现问题是原因是：new zookeeper之后，zookeeper的还没有连接好，就去调用，当然会抛错。

继续查找资料，比较优雅的解决方案为如下：

waitUntilConnected(zooKeeper)；

public static void waitUntilConnected(ZooKeeper zooKeeper) {

        CountDownLatch connectedLatch = new CountDownLatch(1);

        Watcher watcher = new ConnectedWatcher(connectedLatch);

        zooKeeper.register(watcher);

        if (States.CONNECTING == zooKeeper.getState()) {

            try {

                connectedLatch.await();

            } catch (InterruptedException e) {

                throw new IllegalStateException(e);

            }

        }

    }

    static class ConnectedWatcher implements Watcher {

        private CountDownLatch connectedLatch;

        ConnectedWatcher(CountDownLatch connectedLatch) {

            this.connectedLatch = connectedLatch;

        }

        @Override

        public void process(WatchedEvent event) {

            if (event.getState() == KeeperState.SyncConnected) {

                connectedLatch.countDown();

            }

        }

    }