Add a "kernel" plugin for /proc/stat statistics

see #235

plugins/inputs/system/kernel.go

@@ -0,0 +1,110 @@
+// +build linux
+
+package system
+
+import (
+	"bytes"
+	"fmt"
+	"io/ioutil"
+	"os"
+	"strconv"
+
+	"github.com/influxdata/telegraf"
+	"github.com/influxdata/telegraf/plugins/inputs"
+)
+
+// /proc/stat file line prefixes to gather stats on:
+var (
+	interrupts       = []byte("intr")
+	context_switches = []byte("ctxt")
+	processes_forked = []byte("processes")
+	disk_pages       = []byte("page")
+	boot_time        = []byte("btime")
+)
+
+type Kernel struct {
+	statFile string
+}
+
+func (k *Kernel) Description() string {
+	return "Get kernel statistics from /proc/stat"
+}
+
+func (k *Kernel) SampleConfig() string { return "" }
+
+func (k *Kernel) Gather(acc telegraf.Accumulator) error {
+	data, err := k.getProcStat()
+	if err != nil {
+		return err
+	}
+
+	fields := make(map[string]interface{})
+
+	dataFields := bytes.Fields(data)
+	for i, field := range dataFields {
+		switch {
+		case bytes.Equal(field, interrupts):
+			m, err := strconv.Atoi(string(dataFields[i+1]))
+			if err != nil {
+				return err
+			}
+			fields["interrupts"] = int64(m)
+		case bytes.Equal(field, context_switches):
+			m, err := strconv.Atoi(string(dataFields[i+1]))
+			if err != nil {
+				return err
+			}
+			fields["context_switches"] = int64(m)
+		case bytes.Equal(field, processes_forked):
+			m, err := strconv.Atoi(string(dataFields[i+1]))
+			if err != nil {
+				return err
+			}
+			fields["processes_forked"] = int64(m)
+		case bytes.Equal(field, boot_time):
+			m, err := strconv.Atoi(string(dataFields[i+1]))
+			if err != nil {
+				return err
+			}
+			fields["boot_time"] = int64(m)
+		case bytes.Equal(field, disk_pages):
+			in, err := strconv.Atoi(string(dataFields[i+1]))
+			if err != nil {
+				return err
+			}
+			out, err := strconv.Atoi(string(dataFields[i+2]))
+			if err != nil {
+				return err
+			}
+			fields["disk_pages_in"] = int64(in)
+			fields["disk_pages_out"] = int64(out)
+		}
+	}
+
+	acc.AddFields("kernel", fields, map[string]string{})
+
+	return nil
+}
+
+func (k *Kernel) getProcStat() ([]byte, error) {
+	if _, err := os.Stat(k.statFile); os.IsNotExist(err) {
+		return nil, fmt.Errorf("kernel: %s does not exist!", k.statFile)
+	} else if err != nil {
+		return nil, err
+	}
+
+	data, err := ioutil.ReadFile(k.statFile)
+	if err != nil {
+		return nil, err
+	}
+
+	return data, nil
+}
+
+func init() {
+	inputs.Add("kernel", func() telegraf.Input {
+		return &Kernel{
+			statFile: "/proc/stat",
+		}
+	})
+}