Issue MYSQL Memory spike during backup

[thinkjarvis]

Server operating system version

Ubuntu 24.04.3 LTS

Plesk version and microupdate number

Plesk Obsidian Version 18.0.72 Update #2

We are seeing a consistent problem on one of our plesk servers.

When the scheduled backup runs (Set to save locally, databases only). It causes Maria DB/MYSQL memory consumption to jump by several gb. This memory is never flushed or purged.

Over a week - This memory use creeps until mysql and system memory hits over 90% of the ram total. This means that the PHP FPM processes no longer have enough available memory to run - Causing mariadb to crash.

We have had to schedule a nightly restart of mariadb via cron job to ensure that the memory doesnt continually fill.

I think this is a bug in Plesk. Any ideas on what might cause this behaviour or how I can release the alocated memory after a backup? Or just prevent the ram consumption completely?

The spike is the backup running, the sudden drop is our scheduled mariaDB restart.

 

[Kaspar]

MariaDB has a dedicated documentation page on memory usage and how to profile it, which might be a useful read.

Other interesting reads on MaraiDB memory usage are:

Mysterious mariadb 10.4.1 ram ussage

i have upgraded from mariadb 10.1.36 to 10.4.8 and i can see mysterious increasing ram ussage on that new version. I also edited innodb_buffer_pool_size ant seems there is no effect if its set to 1...

stackoverflow.com

MariaDB not releasing RAM after jobs finish

TL:DR - It was likely a problem with Jemalloc not being turned on. Now that Jemalloc is on, the problem appears to have gone away. Whenever I run a job to write to a database in MariaDB, it takes...

stackoverflow.com

 

[thinkjarvis]

@Kaspar jemalloc looks interesting as a solution to the problem - If it can manage the memory pool more efficiently then we may have a winner here.

I am going to speak with our managed hosting providers to see if they can impliment on one of our servers as a test.