Dubbo使用zookeeper原理

dubbo有服务提供者和消费者，二者都会向zookeeper注册，那么他们两个向zookeeper注册了什么，又起到什么作用呢？

在服务启动时，会调用到一个方法：
org.apache.dubbo.registry.zookeeper.ZookeeperRegistry#doRegister

    @Override
    public void doRegister(URL url) {
        try {
            checkDestroyed();
            zkClient.create(toUrlPath(url), url.getParameter(DYNAMIC_KEY, true));
        } catch (Throwable e) {
            throw new RpcException("Failed to register " + url + " to zookeeper " + getUrl() + ", cause: " + e.getMessage(), e);
        }
    }

 org.apache.dubbo.remoting.zookeeper.AbstractZookeeperClient#create(String path, boolean ephemeral)
其中ephemeral表示是否创建临时节点，dubbo选择的是创建临时节点。

    @Override
    public void create(String path, boolean ephemeral) {
        if (!ephemeral) {
            if (persistentExistNodePath.contains(path)) {
                return;
            }
            if (checkExists(path)) {
                persistentExistNodePath.add(path);
                return;
            }
        }
        int i = path.lastIndexOf('/');
        if (i > 0) {
            create(path.substring(0, i), false);
        }
        if (ephemeral) {
            createEphemeral(path);
        } else {
            createPersistent(path);
            persistentExistNodePath.add(path);
        }
    }

服务消费者向zookeeper注册了什么？