Impact on User:
An increase in CPU and Memory usage can result in bad performance of the node in case of custom queries.
Noticed a significant high memory usage and CPU usage for client nodes, when pmm-server is upgraded to 2.22.0.
Steps to reproduce
1) setup server 2.20.0 and setup client node 2.20.0 with pgsql monitoring and custom pgsql queries (using https://github.com/Percona-Lab/pmm-custom-queries), I have used 13.x latest version official pgsql
2) let the system run for some mins, and execute upgrade on pmm-server
3) notice significant increase in memory usage and CPU usage for client node host running postgresql exporter.
Update on the issue:
This increase in memory usage is observed on nodes that have custom queries setup for pgsql client node.