Thank you, I was missing the psutil like you mentioned. I would recommand to make it more abvious in the documentation or maybe as requirement in elasticapm module.
It is specified in the middle of the documentation in metrics as :
if you do **not** use Linux, you need to install [ psutil ](https://pypi.org/project/psutil/) for this metric set.
It is also needed for OSX.
Thanks a lot for your quick feedback.
F.