@Override
                    public void run() throws Exception {
                        try {
                            // if the node doesn't exist we should listen for the root node to reappear
                            exists(path);
                            List<String> children = getChildren(path);
                            listener.handleChildChange(path, children);
                        } catch (ZkNoNodeException e) {
                            listener.handleChildChange(path, null);
                        }
                    }
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