add chrony support (#1238)

* add chrony support

* remove path definition

* add changelog

plugins/inputs/chrony/chrony.go

@@ -0,0 +1,118 @@
+// +build linux
+
+package chrony
+
+import (
+	"errors"
+	"fmt"
+	"os/exec"
+	"strconv"
+	"strings"
+	"time"
+
+	"github.com/influxdata/telegraf"
+	"github.com/influxdata/telegraf/internal"
+	"github.com/influxdata/telegraf/plugins/inputs"
+)
+
+var (
+	execCommand = exec.Command // execCommand is used to mock commands in tests.
+)
+
+type Chrony struct {
+	path string
+}
+
+func (*Chrony) Description() string {
+	return "Get standard chrony metrics, requires chronyc executable."
+}
+
+func (*Chrony) SampleConfig() string {
+	return ""
+}
+
+func (c *Chrony) Gather(acc telegraf.Accumulator) error {
+	if len(c.path) == 0 {
+		return errors.New("chronyc not found: verify that chrony is installed and that chronyc is in your PATH")
+	}
+	cmd := execCommand(c.path, "tracking")
+	out, err := internal.CombinedOutputTimeout(cmd, time.Second*5)
+	if err != nil {
+		return fmt.Errorf("failed to run command %s: %s - %s", strings.Join(cmd.Args, " "), err, string(out))
+	}
+	fields, tags, err := processChronycOutput(string(out))
+	if err != nil {
+		return err
+	}
+	acc.AddFields("chrony", fields, tags)
+	return nil
+}
+
+// processChronycOutput takes in a string output from the chronyc command, like:
+//
+//     Reference ID    : 192.168.1.22 (ntp.example.com)
+//     Stratum         : 3
+//     Ref time (UTC)  : Thu May 12 14:27:07 2016
+//     System time     : 0.000020390 seconds fast of NTP time
+//     Last offset     : +0.000012651 seconds
+//     RMS offset      : 0.000025577 seconds
+//     Frequency       : 16.001 ppm slow
+//     Residual freq   : -0.000 ppm
+//     Skew            : 0.006 ppm
+//     Root delay      : 0.001655 seconds
+//     Root dispersion : 0.003307 seconds
+//     Update interval : 507.2 seconds
+//     Leap status     : Normal
+//
+// The value on the left side of the colon is used as field name, if the first field on
+// the right side is a float. If it cannot be parsed as float, it is a tag name.
+//
+// Ref time is ignored and all names are converted to snake case.
+//
+// It returns (<fields>, <tags>)
+func processChronycOutput(out string) (map[string]interface{}, map[string]string, error) {
+	tags := map[string]string{}
+	fields := map[string]interface{}{}
+	lines := strings.Split(strings.TrimSpace(out), "\n")
+	for _, line := range lines {
+		stats := strings.Split(line, ":")
+		if len(stats) < 2 {
+			return nil, nil, fmt.Errorf("unexpected output from chronyc, expected ':' in %s", out)
+		}
+		name := strings.ToLower(strings.Replace(strings.TrimSpace(stats[0]), " ", "_", -1))
+		// ignore reference time
+		if strings.Contains(name, "time") {
+			continue
+		}
+		valueFields := strings.Fields(stats[1])
+		if len(valueFields) == 0 {
+			return nil, nil, fmt.Errorf("unexpected output from chronyc: %s", out)
+		}
+		if strings.Contains(strings.ToLower(name), "stratum") {
+			tags["stratum"] = valueFields[0]
+			continue
+		}
+		value, err := strconv.ParseFloat(valueFields[0], 64)
+		if err != nil {
+			tags[name] = strings.ToLower(valueFields[0])
+			continue
+		}
+		if strings.Contains(stats[1], "slow") {
+			value = -value
+		}
+		fields[name] = value
+	}
+
+	return fields, tags, nil
+}
+
+func init() {
+	c := Chrony{}
+	path, _ := exec.LookPath("chronyc")
+	if len(path) > 0 {
+		c.path = path
+	}
+	inputs.Add("chrony", func() telegraf.Input {
+		return &c
+	})
+}