Hey, I have a similar issue, the thread is here - https://www.digitalocean.com/community/questions/one-click-install-wordpress-droplet-error-establishing-database-connection-returns

I dont get any issues in the logs, cannot find a reason for mysql spontaneously stopping to work and I am now resizing my droplet, though I am running a cache plugin for Wordpress, I have Cloudflare running for the domain and Wordpress install and my memory seems free and fine, currently and in the monitoring tools.

Hello,

There are a few things that I could suggest:

• In order to fix your current problem I believe that you just need to start your MySQL service:

systemctl start mysql

It most likely crashed due to out of memory problem. You should be able to see the error at:

/var/log/syslog

• Check your access logs for any malicious activity, you could use this script here to summarize your access log:

https://github.com/bobbyiliev/quick_access_logs_summary

• Consider adding a caching plugin like W3 total cache or WP super cache, that way you would reduce the number of requests to your SQL instance as some of your content would be served from static cache.

• Consider increasing the available RAM for your Droplet

• Consider using a CDN service

Hope that this helps! Let me know if you have any questions.
Regards,
Bobby

Hello all,

This crash is most likely due to your system running out of memory. I’d suggest that you add a swap file to give yourself a bit more of a buffer. Check out this tutorial:

How To Add Swap on Ubuntu 18.04

What you can also do is to use the MySQLTuner script.

The MySQLTuner is a script written in Perl and allows you to quickly test your MySQL configuration and it gives you suggestions for adjustments to increase performance and stability.

According to the official GitHub page, it supports 300 indicators for MySQL/MariaDB/Percona Server in this last version.

To run the script you could do the following:

• SSH to your Droplet
• Download the script:

wget http://mysqltuner.pl/ -O mysqltuner.pl

• Then execute it:

perl mysqltuner.pl

The script would run multiple checks against your MySQL instance, all checks done by MySQLTuner are documented here.

Also as stated in the official documentation, it is still extremely important for you to fully understand each change you make to a MySQL database server. If you don’t understand portions of the script’s output, or if you don’t understand the recommendations, you should consult a knowledgeable DBA or system administrator that you trust.

As a good practice make sure to always test your changes on staging environments before implementing them on your production database.

On the same note, if you want to have worry-free MySQL hosting and focus on your application, I would recommend trying out the DigitalOcean Managed Databases:

https://www.digitalocean.com/products/managed-databases-mysql/

Source:
https://www.digitalocean.com/community/questions/how-to-tweak-mysql-mariadb-configuration-for-increased-performance-and-stability

Hope that this helps!
Regards,
Alex