laravel 读操连接了读库和写库

今天在laravel框架中配置读写分离时，发现ORM的读操作分别连接了主库和从库，由于我们的产品是在海外推广，用的AWS 的 RDS Mysql版本，主库在美国，在新加坡开了个从库，发现查询时连接了主库和从库，导致查询非常慢，因此只能通过原生SQL查询。

laravel的读写分离配置如下（database.php)：

'connections' => [

'mysql' => [
'driver'    => 'mysql',
'host'      => env('DB_HOST', 'localhost'),
'port'      => env('DB_PORT', 3306),
'database'  => env('DB_DATABASE', 'forge'),
'username'  => env('DB_USERNAME', 'forge'),
'password'  => env('DB_PASSWORD', ''),
'charset'   => 'utf8mb4',
'collation' => 'utf8mb4_unicode_ci',
'prefix'    => env('DB_PREFIX', 'tbl_'),
'timezone'  => env('DB_TIMEZONE', '+00:00'),
'strict'    => false,
'options'   => array(
PDO::ATTR_STRINGIFY_FETCHES => true,
PDO::ATTR_EMULATE_PREPARES => false
),
],

'mysql-read' => [
'driver'    => 'mysql',
'host'      => env('DB_HOST_READ', 'localhost'),
'port'      => env('DB_PORT', 3306),
'database'  => env('DB_DATABASE', 'forge'),
'username'  => env('DB_USERNAME', 'forge'),
'password'  => env('DB_PASSWORD', ''),
'charset'   => 'utf8mb4',
'collation' => 'utf8mb4_unicode_ci',
'prefix'    => env('DB_PREFIX', 'tbl_'),
'timezone'  => env('DB_TIMEZONE', '+00:00'),
'strict'    => false,
'options'   => array(
PDO::ATTR_STRINGIFY_FETCHES => true,
PDO::ATTR_EMULATE_PREPARES => false
),
],

'mysql-write' => [
'driver'    => 'mysql',
'host'      => env('DB_HOST_WRITE', 'localhost'),
'port'      => env('DB_PORT', 3306),
'database'  => env('DB_DATABASE', 'forge'),
'username'  => env('DB_USERNAME', 'forge'),
'password'  => env('DB_PASSWORD', ''),
'charset'   => 'utf8mb4',
'collation' => 'utf8mb4_unicode_ci',
'prefix'    => env('DB_PREFIX', 'tbl_'),
'timezone'  => env('DB_TIMEZONE', '+00:00'),
'strict'    => false,
'options'   => array(
PDO::ATTR_STRINGIFY_FETCHES => true,
PDO::ATTR_EMULATE_PREPARES => false
),
],
],

建一个连接数据的类：

class DBConnService
{
private static $read_conn = null;
private static $write_conn = null;

private function __construct() {}

public static function writeConn() {
if (self::$write_conn === null) {
self::$write_conn = DB::connection('mysql-write');
}

return self::$write_conn;
}

public static function readConn() {
if (self::$read_conn === null) {
self::$read_conn = DB::connection('mysql-read');
}

return self::$read_conn;
}

}

在程序中使用：

$sql = "SELECT $fields FROM $table WHERE field = ? ";
$result = DBConnService::readConn()->select($sql, [$field]);

这样查询时只连接从库一次，而且一次请求中也只连接从库一次