Fix Linux cpu errors (#606)

Make the Linux cpu collector soft-error on missing `cpufreq` and
`thermal_throttle` features.

collector/cpu_linux.go

@@ -17,9 +17,11 @@ package collector
 
 import (
 	"fmt"
+	"os"
 	"path/filepath"
 
 	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/common/log"
 	"github.com/prometheus/procfs"
 )
 
@@ -99,30 +101,38 @@ func (c *cpuCollector) updateCPUfreq(ch chan<- prometheus.Metric) error {
 	for _, cpu := range cpus {
 		_, cpuname := filepath.Split(cpu)
 
-		if value, err = readUintFromFile(filepath.Join(cpu, "cpufreq/scaling_cur_freq")); err != nil {
-			return err
-		}
-		ch <- prometheus.MustNewConstMetric(c.cpuFreq, prometheus.GaugeValue, float64(value), cpuname)
+		if _, err := os.Stat(filepath.Join(cpu, "cpufreq")); os.IsNotExist(err) {
+			log.Debugf("CPU %q is missing cpufreq", cpu)
+		} else {
+			if value, err = readUintFromFile(filepath.Join(cpu, "cpufreq/scaling_cur_freq")); err != nil {
+				return err
+			}
+			ch <- prometheus.MustNewConstMetric(c.cpuFreq, prometheus.GaugeValue, float64(value), cpuname)
 
-		if value, err = readUintFromFile(filepath.Join(cpu, "cpufreq/scaling_min_freq")); err != nil {
-			return err
-		}
-		ch <- prometheus.MustNewConstMetric(c.cpuFreqMin, prometheus.GaugeValue, float64(value), cpuname)
+			if value, err = readUintFromFile(filepath.Join(cpu, "cpufreq/scaling_min_freq")); err != nil {
+				return err
+			}
+			ch <- prometheus.MustNewConstMetric(c.cpuFreqMin, prometheus.GaugeValue, float64(value), cpuname)
 
-		if value, err = readUintFromFile(filepath.Join(cpu, "cpufreq/scaling_max_freq")); err != nil {
-			return err
+			if value, err = readUintFromFile(filepath.Join(cpu, "cpufreq/scaling_max_freq")); err != nil {
+				return err
+			}
+			ch <- prometheus.MustNewConstMetric(c.cpuFreqMax, prometheus.GaugeValue, float64(value), cpuname)
 		}
-		ch <- prometheus.MustNewConstMetric(c.cpuFreqMax, prometheus.GaugeValue, float64(value), cpuname)
 
-		if value, err = readUintFromFile(filepath.Join(cpu, "thermal_throttle/core_throttle_count")); err != nil {
-			return err
-		}
-		ch <- prometheus.MustNewConstMetric(c.cpuCoreThrottle, prometheus.CounterValue, float64(value), cpuname)
+		if _, err := os.Stat(filepath.Join(cpu, "thermal_throttle")); os.IsNotExist(err) {
+			log.Debugf("CPU %q is missing thermal_throttle", cpu)
+		} else {
+			if value, err = readUintFromFile(filepath.Join(cpu, "thermal_throttle/core_throttle_count")); err != nil {
+				return err
+			}
+			ch <- prometheus.MustNewConstMetric(c.cpuCoreThrottle, prometheus.CounterValue, float64(value), cpuname)
 
-		if value, err = readUintFromFile(filepath.Join(cpu, "thermal_throttle/package_throttle_count")); err != nil {
-			return err
+			if value, err = readUintFromFile(filepath.Join(cpu, "thermal_throttle/package_throttle_count")); err != nil {
+				return err
+			}
+			ch <- prometheus.MustNewConstMetric(c.cpuPackageThrottle, prometheus.CounterValue, float64(value), cpuname)
 		}
-		ch <- prometheus.MustNewConstMetric(c.cpuPackageThrottle, prometheus.CounterValue, float64(value), cpuname)
 	}
 
 	return nil

collector/fixtures/e2e-output.txt

@@ -212,22 +212,27 @@ node_cpu{cpu="cpu7",mode="user"} 290.98
 # TYPE node_cpu_core_throttles_total counter
 node_cpu_core_throttles_total{cpu="cpu0"} 5
 node_cpu_core_throttles_total{cpu="cpu1"} 0
+node_cpu_core_throttles_total{cpu="cpu2"} 40
 # HELP node_cpu_frequency_hertz Current cpu thread frequency in hertz.
 # TYPE node_cpu_frequency_hertz gauge
 node_cpu_frequency_hertz{cpu="cpu0"} 1.699981e+06
 node_cpu_frequency_hertz{cpu="cpu1"} 1.699981e+06
+node_cpu_frequency_hertz{cpu="cpu3"} 8000
 # HELP node_cpu_frequency_max_hertz Maximum cpu thread frequency in hertz.
 # TYPE node_cpu_frequency_max_hertz gauge
 node_cpu_frequency_max_hertz{cpu="cpu0"} 3.7e+06
 node_cpu_frequency_max_hertz{cpu="cpu1"} 3.7e+06
+node_cpu_frequency_max_hertz{cpu="cpu3"} 4.2e+06
 # HELP node_cpu_frequency_min_hertz Minimum cpu thread frequency in hertz.
 # TYPE node_cpu_frequency_min_hertz gauge
 node_cpu_frequency_min_hertz{cpu="cpu0"} 800000
 node_cpu_frequency_min_hertz{cpu="cpu1"} 800000
+node_cpu_frequency_min_hertz{cpu="cpu3"} 1000
 # HELP node_cpu_package_throttles_total Number of times this cpu package has been throttled.
 # TYPE node_cpu_package_throttles_total counter
 node_cpu_package_throttles_total{cpu="cpu0"} 30
 node_cpu_package_throttles_total{cpu="cpu1"} 30
+node_cpu_package_throttles_total{cpu="cpu2"} 6
 # HELP node_disk_bytes_read The total number of bytes read successfully.
 # TYPE node_disk_bytes_read counter
 node_disk_bytes_read{device="dm-0"} 5.13708655616e+11

collector/fixtures/sys/bus/cpu/devices/cpu2/thermal_throttle/core_throttle_count

@@ -0,0 +1 @@
+40

collector/fixtures/sys/bus/cpu/devices/cpu2/thermal_throttle/package_throttle_count

@@ -0,0 +1 @@
+6

collector/fixtures/sys/bus/cpu/devices/cpu3/cpufreq/scaling_cur_freq

@@ -0,0 +1 @@
+8000

collector/fixtures/sys/bus/cpu/devices/cpu3/cpufreq/scaling_max_freq

@@ -0,0 +1 @@
+4200000

collector/fixtures/sys/bus/cpu/devices/cpu3/cpufreq/scaling_min_freq

@@ -0,0 +1 @@
+1000