Hello,

The “Error establishing a database connection” occurs when WordPress is unable to make a connection to the database. A number of things can affect your WordPress database connection.

This issue can be caused by incorrect database information in your WordPress settings, corrupt database, or an irresponsive database server. You can refer to our community article for more information

https://www.digitalocean.com/community/tutorials/how-to-debug-the-wordpress-error-establishing-database-connection

One of the most common reason is MySQL stopped running. It stopped or failed to start as a result of not enough memory.

A useful program to review the logs one page at a time is less, for example:

less /var/log/mysql/error.log

If you see memory issues such as mmap can’t allocate then you can be sure that you are having memory issues. You can choose to optimize your MySQL configuration, or use caching mechanisms to reduce the application’s load on MySQL. If nothing works, you can try resizing your server to a one with higher CPU and RAM.

Hope this helps!

Cheers,
Lalitha

Hello, @sushpawar2500

Have you checked the MySQL error_log in order to see if the server is running out of memory or if the issue is with to many MySQL connections? As per the tutorial you can run this command in order to check if the server have recently run out of memory:

zgrep -a "allocate memory" /var/log/mysql/error.log*

zgrep will search through log files, including older log files that have been archived as compressed .tar.gz files. We’re searching for lines that contain allocate memory, in any error.log* file in the /var/log/mysql/ directory.

You can always login and check the MySQL error_log when the issue occurs using tail to either check the last 100 entries in the log or monitor the log in real time:

tail -n 100 /var/log/mysql/error.log

and monitor it in real time:

tail -f /var/log/mysql/error.log

Hope that this helps!
Regards,
Alex