Prometheus uses HTTP on the same server where HTTP is the main application under observation. This is from the Prometheus docs:

I'm not inclined to install an application which relies on HTTP at the data transport layer to monitor a LAMP application where HTTP and apache2 are at the core of the problem. However, for a different scenario, an HTTP-transport based monitoring system might be "just the ticket".

Thanks for the ideas, but I'm sticking with MQTT and Node-RED for the time being. MQTT is very lightweight on the server and it does not use HTTP; but instead uses a light-weight TCP connection, which I prefer, but that is just me.

I complete agree with you that:

Except I would change your second comment to read more like:

For all but the most trivial problems, we need to drill down into the system. Time series graphs and charts are only indicators. The story continues past indicators for all but the most trivial issues we encounter .......

I'm pretty sure you agree. After all, if we only needed third party time series graphing tools to solve problems, we could hire 12 year old kids to manage our networks and servers , and we could do other tasks more fun and interesting tasks

But on the other hand, when we work in network and system management (whatever we are doing or where ever we are working), we always encounter new and very interesting problems and the more complex networks become, the more interesting the problems are.