I found some time to play around with the new prometheus special agents and the prometheus_custom check. I had to configure a “dummy” host for this and use the piggyback option to connect the service with other hosts. This dummy host was configured with “no agent but all configured special agents”.
The connection to prometheus works and writes the piggyback data file.
After a while I recognize that the values are everytime the same. The problem was that the piggyback file was not updated regulary. If I run cmk -vpn PROMETHEUS_HOST it gets updated but not every 60s.
After changing the host to “with agent and all configured special agents” it works now.
I am pretty sure that other special agents works without any host agent. Has anyone else tried this? If you have any suggestions what I did wrong please help me If this looks like a bug / point to improve let me know how to help with this.