[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:330
#2: Bitrix\Main\DB\Connection->query(string)
	/home/bitrix/www/bitrix/modules/main/lib/db/mysqlcommonconnection.php:274
#3: Bitrix\Main\DB\MysqlCommonConnection->lock(string)
	/home/bitrix/www/bitrix/modules/main/lib/composite/internals/locker.php:24
#4: Bitrix\Main\Composite\Internals\Locker::lock(string)
	/home/bitrix/www/bitrix/modules/main/lib/composite/engine.php:477
#5: Bitrix\Main\Composite\Engine::processPageContent(string)
	/home/bitrix/www/bitrix/modules/main/lib/composite/engine.php:424
#6: Bitrix\Main\Composite\Engine::endBuffering(string, string)
	/home/bitrix/www/bitrix/modules/main/classes/general/main.php:3223
#7: CAllMain->EndBufferContent(string)
	/home/bitrix/www/bitrix/modules/main/classes/general/main.php:3167
#8: CAllMain->EndBufferContentMan()
	/home/bitrix/www/bitrix/modules/main/include/epilog_after.php:43
#9: require(string)
	/home/bitrix/www/bitrix/modules/main/include/epilog.php:3
#10: require_once(string)
	/home/bitrix/www/bitrix/footer.php:4
#11: require(string)
	/home/bitrix/www/catalog/index.php:885
#12: include_once(string)
	/home/bitrix/www/bitrix/modules/main/include/urlrewrite.php:159
#13: include_once(string)
	/home/bitrix/www/bitrix/urlrewrite.php:2

Fatal error: Uncaught Bitrix\Main\DB\SqlQueryException: Mysql query error: (2006) MySQL server has gone away in /home/bitrix/www/bitrix/modules/main/lib/db/mysqliconnection.php:137 Stack trace: #0 /home/bitrix/www/bitrix/modules/main/lib/db/connection.php(330): Bitrix\Main\DB\MysqliConnection->queryInternal('DELETE FROM `b_...', Array, NULL) #1 /home/bitrix/www/bitrix/modules/main/lib/db/connection.php(379): Bitrix\Main\DB\Connection->query('DELETE FROM `b_...', NULL) #2 /home/bitrix/www/bitrix/modules/main/lib/orm/data/datamanager.php(1624): Bitrix\Main\DB\Connection->queryExecute('DELETE FROM `b_...') #3 /home/bitrix/www/bitrix/modules/security/classes/general/session_db.php(100): Bitrix\Main\ORM\Data\DataManager::delete(Array) #4 /home/bitrix/www/bitrix/modules/security/classes/general/session_handler.php(28): CSecuritySessionDB::write('WPbhnqIcvkqvhct...', 'SESS_AUTH|a:1:{...') #5 [internal function]: CSecuritySessionHandler->write('WPbhnqIcvkqvhct...', 'SESS_AUTH|a:1:{...') #6 [internal function]: session_write_close in /home/bitrix/www/bitrix/modules/main/lib/db/mysqliconnection.php on line 137