How to use nginx as a load balancer for mysql

./configure --prefix=/Data/apps/nginx --with-http_stub_status_module --with-http_ssl_module --with-http_realip_module --with-http_image_filter_module --with-stream

stream{
include /Data/apps/nginx/conf/stream/*.conf;
}

server {
listen 3307; #Note that the port cannot be the same as the one that mysql listens to proxy_pass db;
}
upstream db {
server 127.0.0.1:3306;
server 192.168.233.1:3306;
}

#In fact, when creating new mysqli, you only need to change the port number to the same as the port number set by nginx reverse proxy. $mysqli = new mysqli('127.0.0.1','root','root','test',3307);

<?php
class MysqlClass
{
private static $obj = NULL; //mysqlclass object public $host;
public $database;
public $user;
public $pwd;
public $port;
public $mysqli = NULL;
//Prohibit objects from being cloned private function __clone(){}
//Prohibit external instantiation private function __construct($host="127.0.0.1",$database="test",$user="root",$pwd="root",$port="3307")
{
$this->host = $host;
$this->database = $database;
$this->user = $user;
$this->pwd = $pwd;
$this->port = $port;
$this->mysqli = $this->db_connect();
}
//Get mysqli connection private function db_connect()
{
$mysqli = new mysqli($this->host,$this->user,$this->pwd,$this->database,$this->port);
if($mysqli->connect_errno)
{
printf("Connect failed: %s\n", $mysqli->connect_errno);
exit();
}
$mysqli->query("set names utf8 ");
return $mysqli;
}
//Get the db instance public static function get_db()
{
if(self::$obj === NULL)
{
self::$obj = new self();
}
return self::$obj;
}
public function db_query($sql)
{
$result = $this->mysqli->query($sql);
$arr = [];
while ($row = $result->fetch_assoc()) {
$arr[] = $row;
}
$result->close();
$this->mysqli->close();
return $arr;
}
public function db_insert()
{
}
public function db_update()
{
}
public function __destruct() {
$this->mysqli->close();
}
}
$db = MysqlClass::get_db();
$r = $db->db_query("show tables");
var_dump($r);