[Bitrix\Main\DB\ConnectionException] 
Mysql connect error: Unknown MySQL server host 'mysqlserver' (4) (400)
#0: Bitrix\Main\DB\MysqlConnection->connectInternal()
	/home/www/z171617/htdocs/bitrix/modules/main/lib/db/mysqlconnection.php:74
#1: Bitrix\Main\DB\MysqlConnection->queryInternal(string, array, NULL)
	/home/www/z171617/htdocs/bitrix/modules/main/lib/db/connection.php:235
#2: Bitrix\Main\DB\Connection->query(string)
	/home/www/z171617/htdocs/bitrix/modules/main/lib/config/option.php:150
#3: Bitrix\Main\Config\Option::load(string, NULL)
	/home/www/z171617/htdocs/bitrix/modules/main/lib/config/option.php:36
#4: Bitrix\Main\Config\Option::get(string, string, string)
	/home/www/z171617/htdocs/bitrix/modules/main/lib/httprequest.php:279
#5: Bitrix\Main\HttpRequest->prepareCookie(array)
	/home/www/z171617/htdocs/bitrix/modules/main/lib/httprequest.php:64
#6: Bitrix\Main\HttpRequest->__construct(object, array, array, array, array)
	/home/www/z171617/htdocs/bitrix/modules/main/lib/httpapplication.php:43
#7: Bitrix\Main\HttpApplication->initializeContext(array)
	/home/www/z171617/htdocs/bitrix/modules/main/lib/application.php:122
#8: Bitrix\Main\Application->initializeExtendedKernel(array)
	/home/www/z171617/htdocs/bitrix/modules/main/include.php:1
#9: require_once(string)
	/home/www/z171617/htdocs/bitrix/modules/main/include/prolog_before.php:14
#10: require_once(string)
	/home/www/z171617/htdocs/bitrix/modules/main/include/prolog.php:11
#11: require_once(string)
	/home/www/z171617/htdocs/bitrix/header.php:1
#12: require(string)
	/home/www/z171617/htdocs/index.php:2