So primary means currently is using a reverse proxy and limiting there.
I guess that should work.
Yes, for Data Prepper 1.1, securing it with a reverse proxy is a solution. If HTTP Basic authentication is sufficient for your needs, it will be available in version 1.2 (scheduled for Dec 7th).
Only thing left would be to make sure that client X cannot send data which looks like data from customer Y. Any suggestions here, or is that not possible?
Are you looking for something like RBAC where different clients are allowed access to different pipelines? You can do something similar by creating different pipelines. You could then have different username/passwords on the OTel Trace Sources. Presently Data Prepper does not support multiple sources, so the pipelines would have to be duplicated. GitHub issue #406 is a feature request for multiple sources. Please comment or upvote it if this looks like it would be helpful for your use-case.
If you are looking for something else, you can also create a Feature Request in GitHub. I’d like to discuss what your needs are and how Data Prepper can meet them.