Changes to Open Files handling in Mongo 4.4

Hi All,

We have recently upgraded MongoDB from 4.2 to 4.4. As we have a very large number of databases and collections, we have typically had the service file for the mongodb automation agent include support for handing more files / processes by having LimitNOFILE and LimitNPROC set to 500000.

Our Open Files used profile typically looks like this for a Replica:

As from the time of installing 4.4, we can see a completely different type of usage profile. It looks like Open Files are being closed more aggressively. I looked through the release notes for the Mongo 4.4, but could find nothing on this. Does anyone know if there was change implemented? If not, is there another way to explain this change in behaviour?