MySQL / MariaDB max_open_files more than 1024
For me the issue was MySQL max_open_files more than 1024
https://unix.stackexchange.com/questions/152186/mysql-max-open-files-more-than-1024
Edit /etc/security/limits.conf
and add the following lines
mysql soft nofile 65535
mysql hard nofile 65535
then reboot.
Then edit /etc/systemd/system/mysqld.service
and add
LimitNOFILE=infinity
LimitMEMLOCK=infinity
Then restart the db service:
sudo systemctl reload mariadb.service