Dear Jasper, thanks for you quick reply. It's great to know I can use this without abusing it.
As for your last question, I'm not using the feature yet, but I was planning to create markers via API calls.
The ETL is script-based, so it should be relatively easy to do this via curl calls. I've just gone through the documentation and obtained a working token, with a Self Client registration.
The original problem is to measure resource consumption of various processes in this ETL.
In principle, I could collect metrics about a process (and all its sub-processes) with the usual Linux tools, and then make my own plots. The biggest obstacle to this approach is that the ETL triggers activities from processes that are not in the same process tree. In particular the most resource-hungry ones are database processes that are managed by a completely detached daemon. So direct measuring of something that is not in the same process tree and then try to make sense of the big picture becomes cumbersome.
I thought it would be much easier to simply mark the start and the end of each task in the already available metrics in site24x7. Then I can just look at spikes in a plot and see what tasks were running at that moment.