Netdata is scalable distributed realtime performance & health monitoring system
netdata collects and visualizes metrics.
If it is a number and it can be collected somehow, netdata can visualize it.
Out of the box, it comes with plugins that collect hundreds of
system metrics and metrics of popular applications.
Netdata is very resource efficient and you can control its resource consumption.
It will use some spare CPU cycles, usually just 1-3% of a single core,
the RAM you want it have, and no disk I/O at all, apart its logging. 

WWW: https://github.com/firehol/netdata