Zookeeper KeeperErrorCode = ConnectionLoss

winson

　　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();
　　}
　　}
　　}