collector/cpu: split cpu freq metrics into separate collector (#1253)

The cpu frequency information is not always needed and/or available.
This change allows the cpu frequency metrics to be enabled/disabled
separately from the other cpu metrics, and also prevents a frequency
metric failure (such as a parse error) from failing the main cpu
collector.

Fixes #1241

Signed-off-by: Paul Gier <pgier@redhat.com>

collector/cpufreq_linux.go

@@ -0,0 +1,139 @@
+// Copyright 2019 The Prometheus Authors
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// +build !nocpu
+
+package collector
+
+import (
+	"fmt"
+
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/procfs/sysfs"
+)
+
+type cpuFreqCollector struct {
+	cpuFreq        *prometheus.Desc
+	cpuFreqMin     *prometheus.Desc
+	cpuFreqMax     *prometheus.Desc
+	scalingFreq    *prometheus.Desc
+	scalingFreqMin *prometheus.Desc
+	scalingFreqMax *prometheus.Desc
+}
+
+func init() {
+	registerCollector("cpufreq", defaultEnabled, NewCPUFreqCollector)
+}
+
+// NewCPUFreqCollector returns a new Collector exposing kernel/system statistics.
+func NewCPUFreqCollector() (Collector, error) {
+	return &cpuFreqCollector{
+		cpuFreq: prometheus.NewDesc(
+			prometheus.BuildFQName(namespace, cpuCollectorSubsystem, "frequency_hertz"),
+			"Current cpu thread frequency in hertz.",
+			[]string{"cpu"}, nil,
+		),
+		cpuFreqMin: prometheus.NewDesc(
+			prometheus.BuildFQName(namespace, cpuCollectorSubsystem, "frequency_min_hertz"),
+			"Minimum cpu thread frequency in hertz.",
+			[]string{"cpu"}, nil,
+		),
+		cpuFreqMax: prometheus.NewDesc(
+			prometheus.BuildFQName(namespace, cpuCollectorSubsystem, "frequency_max_hertz"),
+			"Maximum cpu thread frequency in hertz.",
+			[]string{"cpu"}, nil,
+		),
+		scalingFreq: prometheus.NewDesc(
+			prometheus.BuildFQName(namespace, cpuCollectorSubsystem, "scaling_frequency_hertz"),
+			"Current scaled cpu thread frequency in hertz.",
+			[]string{"cpu"}, nil,
+		),
+		scalingFreqMin: prometheus.NewDesc(
+			prometheus.BuildFQName(namespace, cpuCollectorSubsystem, "scaling_frequency_min_hrts"),
+			"Minimum scaled cpu thread frequency in hertz.",
+			[]string{"cpu"}, nil,
+		),
+		scalingFreqMax: prometheus.NewDesc(
+			prometheus.BuildFQName(namespace, cpuCollectorSubsystem, "scaling_frequency_max_hrts"),
+			"Maximum scaled cpu thread frequency in hertz.",
+			[]string{"cpu"}, nil,
+		),
+	}, nil
+}
+
+// Update implements Collector and exposes cpu related metrics from /proc/stat and /sys/.../cpu/.
+func (c *cpuFreqCollector) Update(ch chan<- prometheus.Metric) error {
+	fs, err := sysfs.NewFS(*sysPath)
+	if err != nil {
+		return fmt.Errorf("failed to open sysfs: %v", err)
+	}
+
+	cpuFreqs, err := fs.NewSystemCpufreq()
+	if err != nil {
+		return err
+	}
+
+	// sysfs cpufreq values are kHz, thus multiply by 1000 to export base units (hz).
+	// See https://www.kernel.org/doc/Documentation/cpu-freq/user-guide.txt
+	for _, stats := range cpuFreqs {
+		if stats.CpuinfoCurrentFrequency != nil {
+			ch <- prometheus.MustNewConstMetric(
+				c.cpuFreq,
+				prometheus.GaugeValue,
+				float64(*stats.CpuinfoCurrentFrequency)*1000.0,
+				stats.Name,
+			)
+		}
+		if stats.CpuinfoMinimumFrequency != nil {
+			ch <- prometheus.MustNewConstMetric(
+				c.cpuFreqMin,
+				prometheus.GaugeValue,
+				float64(*stats.CpuinfoMinimumFrequency)*1000.0,
+				stats.Name,
+			)
+		}
+		if stats.CpuinfoMaximumFrequency != nil {
+			ch <- prometheus.MustNewConstMetric(
+				c.cpuFreqMax,
+				prometheus.GaugeValue,
+				float64(*stats.CpuinfoMaximumFrequency)*1000.0,
+				stats.Name,
+			)
+		}
+		if stats.ScalingCurrentFrequency != nil {
+			ch <- prometheus.MustNewConstMetric(
+				c.scalingFreq,
+				prometheus.GaugeValue,
+				float64(*stats.ScalingCurrentFrequency)*1000.0,
+				stats.Name,
+			)
+		}
+		if stats.ScalingMinimumFrequency != nil {
+			ch <- prometheus.MustNewConstMetric(
+				c.scalingFreqMin,
+				prometheus.GaugeValue,
+				float64(*stats.ScalingMinimumFrequency)*1000.0,
+				stats.Name,
+			)
+		}
+		if stats.ScalingMaximumFrequency != nil {
+			ch <- prometheus.MustNewConstMetric(
+				c.scalingFreqMax,
+				prometheus.GaugeValue,
+				float64(*stats.ScalingMaximumFrequency)*1000.0,
+				stats.Name,
+			)
+		}
+	}
+	return nil
+}