Issue Error 500 Plesk\Exception\Database (DB query failed: SQLSTATE[HY000] [2002] Connection refused)

[jaumealcantarago]

Server operating system version

Ubuntu 22.04

Plesk version and microupdate number

Plesk Obsidian Version 18.0.56 Update #3

Hello everyone, the problem I'm having is the following: I have a Linux VPS managed by Plesk. There are different users on this server since it's dedicated to my company.
The error occurs when one of my employees accesses the server through Plesk or when they access a WordPress project on the server, but it only happens to them. We thought it was related to their public IP and found the temporary solution of using WARP, but the same thing still happens. After reviewing logs, etc., we can't find out why only this person from their home accesses the VPS and the database server crashes. I've attached an image of the error here.

Once we restart the entire server or the MariaDB server, it starts working again and can operate without problems.

 

[Raul A.]

Hi,

The error in the screenshot indicates Plesk can't connect to the database service. Check the status of MariaDB. Did it restart recently?

Do you have enough RAM on the VPS? OOM (Out Of Memory) events can kill the database service process and can even damage the InnoDB storage in the process. OOM events occur when the processes on the VPS try to allocate more than the available RAM and generally kill processes with the most used RAM.

 

[jaumealcantarago]

Hi,

The error in the screenshot indicates Plesk can't connect to the database service. Check the status of MariaDB. Did it restart recently?

Do you have enough RAM on the VPS? OOM (Out Of Memory) events can kill the database service process and can even damage the InnoDB storage in the process. OOM events occur when the processes on the VPS try to allocate more than the available RAM and generally kill processes with the most used RAM.

The problem is that in this case it should always happen and this only happens when a colleague accesses from a complete IP, for example there are 3 more people who access to perform different tasks and MariaDB never goes down

 

[Raul A.]

The first step is to verify that the MariaDB service is working correctly. If it restarts when the 4th Plesk user connects then you need to find out why. MariaDB can support up to 200 concurrent connections at any given time with the default configuration.

If you have the time stamp when it last happened, check if MariaDB was restarted around that time.

 

[jaumealcantarago]

El primer paso es verificar que el servicio MariaDB funcione correctamente. Si se reinicia al conectar el cuarto usuario de Plesk, deberá averiguar el motivo. MariaDB admite hasta 200 conexiones simultáneas con la configuración predeterminada.

Si tiene la marca de tiempo de cuándo ocurrió por última vez, verifique si MariaDB se reinició aproximadamente en ese momento.

No se reinicia solo, simplemente lo reiniciamos nosotros mismos y todo vuelve a la normalidad.

 

[Raul A.]

Interesting.
When it happens, connect to the database service and check the number of active processes:

plesk db "show full processlist;"  | cat

In the meantime, check if you don't have a small connection limit:

plesk db "select @@max_connections; select @@max_user_connections;"