讀寫分離 （共兩個資料庫）

'mysql' => [
    'driver' => 'mysql',
    'url' => env('DATABASE_URL'),
    'read' => [
        'host' => [
            '172.17.0.1',
        ],
    ],
    'write' => [
        'host' => [
            env('DB_HOST', '127.0.0.1'),
        ],
    ],
		'sticky' => true,                 // important
    'port' => env('DB_PORT', '3306'),
    'database' => env('DB_DATABASE', 'forge'),
    'username' => env('DB_USERNAME', 'forge'),
    'password' => env('DB_PASSWORD', ''),
    'unix_socket' => env('DB_SOCKET', ''),
    'charset' => 'utf8',
    'collation' => 'utf8_unicode_ci',
    'prefix' => '',
    'prefix_indexes' => true,
    'strict' => true,
    'engine' => null,
    
],

Resource

Laravel Read / Write Connections use multi-database