Scrape thermal_zone temperatures (#1425)

* Scrape thermal_zone temperatures

Signed-off-by: Richard Kojedzinszky <richard@kojedz.in>

collector/thermal_zone_linux.go

@@ -0,0 +1,68 @@
+// 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 !nothermalzone
+
+package collector
+
+import (
+	"fmt"
+
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/procfs/sysfs"
+)
+
+type thermalZoneCollector struct {
+	fs       sysfs.FS
+	zoneTemp *prometheus.Desc
+}
+
+func init() {
+	registerCollector("thermal_zone", defaultEnabled, NewThermalZoneCollector)
+}
+
+// NewThermalZoneCollector returns a new Collector exposing kernel/system statistics.
+func NewThermalZoneCollector() (Collector, error) {
+	fs, err := sysfs.NewFS(*sysPath)
+	if err != nil {
+		return nil, fmt.Errorf("failed to open sysfs: %v", err)
+	}
+
+	return &thermalZoneCollector{
+		fs: fs,
+		zoneTemp: prometheus.NewDesc(
+			prometheus.BuildFQName(namespace, "thermal_zone", "temp"),
+			"Zone temperature in Celsius",
+			[]string{"zone", "type"}, nil,
+		),
+	}, nil
+}
+
+func (c *thermalZoneCollector) Update(ch chan<- prometheus.Metric) error {
+	thermalZones, err := c.fs.ClassThermalZoneStats()
+	if err != nil {
+		return err
+	}
+
+	for _, stats := range thermalZones {
+		ch <- prometheus.MustNewConstMetric(
+			c.zoneTemp,
+			prometheus.GaugeValue,
+			float64(stats.Temp)/1000.0,
+			stats.Name,
+			stats.Type,
+		)
+	}
+
+	return nil
+}