После обновление с 7.1 на 7.3 сайт лег, похоже какие-то проблемы с SQL:
[Bitrix\Main\DB\ConnectionException] Mysql connect error [localhost]: (2002) Connection refused (400)
/home/bitrix/www/bitrix/modules/main/lib/db/mysqliconnection .php:65
#0: Bitrix\Main\DB\MysqliConnection->connectInternal()
/home/bitrix/www/bitrix/modules/main/lib/db/mysqliconnection .php:122
#1: Bitrix\Main\DB\MysqliConnection->queryInternal(string, array, NULL)
/home/bitrix/www/bitrix/modules/main/lib/db/connection.php:329
#2: Bitrix\Main\DB\Connection->query(string)
/home/bitrix/www/bitrix/modules/main/lib/config/option.php:226
#3: Bitrix\Main\Config\Option::load(string, NULL)
/home/bitrix/www/bitrix/modules/main/lib/config/option.php:53
#4: Bitrix\Main\Config\Option::get(string, string, string)
/home/bitrix/www/bitrix/modules/main/lib/httprequest.php:339
#5: Bitrix\Main\HttpRequest->prepareCookie(array)
/home/bitrix/www/bitrix/modules/main/lib/httprequest.php:63
#6: Bitrix\Main\HttpRequest->__construct(object, array, array, array, array)
/home/bitrix/www/bitrix/modules/main/lib/httpapplication.php:42
#7: Bitrix\Main\HttpApplication->initializeContext(array)
/home/bitrix/www/bitrix/modules/main/lib/application.php:122
#8: Bitrix\Main\Application->initializeExtendedKernel(array)
/home/bitrix/www/bitrix/modules/main/include.php:23
#9: require_once(string)
/home/bitrix/www/bitrix/modules/main/include/prolog_admin_be fore.php:18
#10: require_once(string)
/home/bitrix/www/bitrix/modules/main/interface/desktop.php:2
#11: require(string)
/home/bitrix/www/bitrix/admin/index.php:2
[Bitrix\Main\DB\ConnectionException] Mysql connect error [localhost]: (2002) Connection refused (400)
/home/bitrix/www/bitrix/modules/main/lib/db/mysqliconnection
#0: Bitrix\Main\DB\MysqliConnection->connectInternal()
/home/bitrix/www/bitrix/modules/main/lib/db/mysqliconnection
#1: Bitrix\Main\DB\MysqliConnection->queryInternal(string, array, NULL)
/home/bitrix/www/bitrix/modules/main/lib/db/connection.php:329
#2: Bitrix\Main\DB\Connection->query(string)
/home/bitrix/www/bitrix/modules/main/lib/config/option.php:226
#3: Bitrix\Main\Config\Option::load(string, NULL)
/home/bitrix/www/bitrix/modules/main/lib/config/option.php:53
#4: Bitrix\Main\Config\Option::get(string, string, string)
/home/bitrix/www/bitrix/modules/main/lib/httprequest.php:339
#5: Bitrix\Main\HttpRequest->prepareCookie(array)
/home/bitrix/www/bitrix/modules/main/lib/httprequest.php:63
#6: Bitrix\Main\HttpRequest->__construct(object, array, array, array, array)
/home/bitrix/www/bitrix/modules/main/lib/httpapplication.php:42
#7: Bitrix\Main\HttpApplication->initializeContext(array)
/home/bitrix/www/bitrix/modules/main/lib/application.php:122
#8: Bitrix\Main\Application->initializeExtendedKernel(array)
/home/bitrix/www/bitrix/modules/main/include.php:23
#9: require_once(string)
/home/bitrix/www/bitrix/modules/main/include/prolog_admin_be
#10: require_once(string)
/home/bitrix/www/bitrix/modules/main/interface/desktop.php:2
#11: require(string)
/home/bitrix/www/bitrix/admin/index.php:2