@Override
  public void close() {
    pool.close();
    // we need to release tManagers for AsyncThriftClientFactory
    if (pool.getFactory() instanceof AsyncThriftClientFactory) {
      ((AsyncThriftClientFactory<K, V>) pool.getFactory()).close();
    }
  }
return a client V for node K to the {@link ClientManager}.

<p>Note: We do not define this interface in {@link IClientManager} to make you aware that the
return of a client is automatic whenever a particular client is used.
iotdb-core/node-commons/src/main/java/org/apache/iotdb/commons/client/ClientManager.java