Lab – Operators, Vector Matching, Aggregators question no 8

Observability And Monitoring
#1

Hi Team,

In prometheus lab ( Lab – Operators, Vector Matching, Aggregators question no 8) - Construct a query that will show the number of CPUs on each instance across all jobs.
The solution given is - count by (instance) (node_cpu_seconds_total{mode=“idle”}).
Why is it neccessary to provide {mode=“idle”} parameter? In solution they have asked to select some arbitrary mode like idle.
Can anyone explain…

Thanks!!

#2

The explanation is given in the solution for Q7

With the node_cpu_seconds_total metric match one of the modes, doesn’t matter which one. This will show a time series for each cpu for that mode.

All CPUs will export metrics for all modes. Run the query as-is in prometheus - you will get 36

If you take away the mode label, you will get 288

288 / 36 = 8, so there are 8 modes that are being monitored. Selecting any of the available modes should return the answer to 36