private void acquireEventLock() {
        try {
            getEventLock().lockInterruptibly();
        } catch (InterruptedException e) {
            throw new ZkInterruptedException(e);
        }
    }
Counts number of children for the given path.

@param path
@return number of children or 0 if path does not exist.
shared/common/src/main/java/com/alibaba/otter/shared/common/utils/zookeeper/ZkClientx.java