DB reconnect failed

I'm writing a data monitor script work with CLI this week,

Code:

$this->load->database();

#####################################
running 10mins, and local ip changed.
#####################################

// need re-connnect database
$this->db->reconnect();

var_dump($this->db->conn_id)

// bool(false);

$this->db->select('name')->where_in('id', $array)->get('table')->result_array();

// Severity: error --> Exception: Call to a member function real_escape_string() on boolean path\system\database\drivers\mysqli\mysqli_driver.php 344

OK, it's looks like the re-connect was failed.

Why does this error occur? How to deal with it?