feat: expose cpu frequency governor metrics

[lukasCoppens]

Currently there are no metrics exposed about the CPU frequency governor(s). This PR exposes metrics with info about the available governors and indicate which one is in use. It also fixes inconsistencies in the description of some of the metrics exposed by the changed collector.

Adding a mention per the guidelines: @SuperQ, @discordianfish

Signed-off-by: Lukas Coppens [email protected]

[lukasCoppens]

Hi @SuperQ , @discordianfish

Could one of you take a look at this? If any changes are needed I'm happy to implement them!

[rfpronk]

This is exactly what I was looking to get information about which of our nodes need to new settings to be applied.
I've locally rebased (can't write to this branch) this PR after #2587 and build it. Works like a charm 👍

diff on current master branch

diff --git a/collector/cpufreq_common.go b/collector/cpufreq_common.go
index 8a6d7ce..59ee5d9 100644
--- a/collector/cpufreq_common.go
+++ b/collector/cpufreq_common.go
@@ -51,4 +51,9 @@ var (
 		"Maximum scaled CPU thread frequency in hertz.",
 		[]string{"cpu"}, nil,
 	)
+  scalingGovernor = prometheus.NewDesc(
+    prometheus.BuildFQName(namespace, cpuCollectorSubsystem, "scaling_governor"),
+    "Current enabled CPU frequency governor.",
+    []string{"cpu", "governor"}, nil,
+  )
 )
diff --git a/collector/cpufreq_linux.go b/collector/cpufreq_linux.go
index 41ebfe2..266b946 100644
--- a/collector/cpufreq_linux.go
+++ b/collector/cpufreq_linux.go
@@ -18,6 +18,7 @@ package collector

 import (
 	"fmt"
+	"strings"
 	"github.com/go-kit/log"
 	"github.com/prometheus/client_golang/prometheus"
@@ -104,6 +105,22 @@ func (c *cpuFreqCollector) Update(ch chan<- prometheus.Metric) error {
 				stats.Name,
 			)
 		}
+    if stats.Governor != "" {
+			availableGovernors := strings.Split(stats.AvailableGovernors, " ")
+			for _, g := range availableGovernors {
+				state := 0
+				if g == stats.Governor {
+					state = 1
+				}
+				ch <- prometheus.MustNewConstMetric(
+					scalingGovernor,
+					prometheus.GaugeValue,
+					float64(state),
+					stats.Name,
+					g,
+				)
+			}
+		}
 	}
 	return nil
 }

[discordianfish]

Thanks, LGTM!

[discordianfish]

Needs rebasing though

[lukasCoppens]

@discordianfish, @SuperQ I have synced the branch with the current master branch could you take a look again?

[SuperQ]

Nice