RFR: Initial support for ZFS on FreeBSD (#1224)

* WIP: Initial support for ZFS on FreeBSD

* Added build directives

* Ignore 'kstatPath' config option on FreeBSD

* Added tests for ZFS FreeBSD input plugin.

* Updated the README to confrom with the guidelines and added FreeBSD info

* Fixed indents

* Spell check

plugins/inputs/zfs/zfs_freebsd.go

@@ -0,0 +1,140 @@
+// +build freebsd
+
+package zfs
+
+import (
+	"bytes"
+	"fmt"
+	"os/exec"
+	"strconv"
+	"strings"
+
+	"github.com/influxdata/telegraf"
+	"github.com/influxdata/telegraf/plugins/inputs"
+)
+
+func (z *Zfs) gatherPoolStats(acc telegraf.Accumulator) (string, error) {
+
+	lines, err := z.zpool()
+	if err != nil {
+		return "", err
+	}
+
+	pools := []string{}
+	for _, line := range lines {
+		col := strings.Split(line, "\t")
+
+		pools = append(pools, col[0])
+	}
+
+	if z.PoolMetrics {
+		for _, line := range lines {
+			col := strings.Split(line, "\t")
+			tags := map[string]string{"pool": col[0], "health": col[8]}
+			fields := map[string]interface{}{}
+
+			size, err := strconv.ParseInt(col[1], 10, 64)
+			if err != nil {
+				return "", fmt.Errorf("Error parsing size: %s", err)
+			}
+			fields["size"] = size
+
+			alloc, err := strconv.ParseInt(col[2], 10, 64)
+			if err != nil {
+				return "", fmt.Errorf("Error parsing allocation: %s", err)
+			}
+			fields["allocated"] = alloc
+
+			free, err := strconv.ParseInt(col[3], 10, 64)
+			if err != nil {
+				return "", fmt.Errorf("Error parsing free: %s", err)
+			}
+			fields["free"] = free
+
+			frag, err := strconv.ParseInt(strings.TrimSuffix(col[5], "%"), 10, 0)
+			if err != nil { // This might be - for RO devs
+				frag = 0
+			}
+			fields["fragmentation"] = frag
+
+			capval, err := strconv.ParseInt(col[6], 10, 0)
+			if err != nil {
+				return "", fmt.Errorf("Error parsing capacity: %s", err)
+			}
+			fields["capacity"] = capval
+
+			dedup, err := strconv.ParseFloat(strings.TrimSuffix(col[7], "x"), 32)
+			if err != nil {
+				return "", fmt.Errorf("Error parsing dedupratio: %s", err)
+			}
+			fields["dedupratio"] = dedup
+
+			acc.AddFields("zfs_pool", fields, tags)
+		}
+	}
+
+	return strings.Join(pools, "::"), nil
+}
+
+func (z *Zfs) Gather(acc telegraf.Accumulator) error {
+	kstatMetrics := z.KstatMetrics
+	if len(kstatMetrics) == 0 {
+		kstatMetrics = []string{"arcstats", "zfetchstats", "vdev_cache_stats"}
+	}
+
+	tags := map[string]string{}
+	poolNames, err := z.gatherPoolStats(acc)
+	if err != nil {
+		return err
+	}
+	tags["pools"] = poolNames
+
+	fields := make(map[string]interface{})
+	for _, metric := range kstatMetrics {
+		stdout, err := z.sysctl(metric)
+		if err != nil {
+			return err
+		}
+		for _, line := range stdout {
+			rawData := strings.Split(line, ": ")
+			key := metric + "_" + strings.Split(rawData[0], ".")[4]
+			value, _ := strconv.ParseInt(rawData[1], 10, 64)
+			fields[key] = value
+		}
+	}
+	acc.AddFields("zfs", fields, tags)
+	return nil
+}
+
+func run(command string, args ...string) ([]string, error) {
+	cmd := exec.Command(command, args...)
+	var outbuf, errbuf bytes.Buffer
+	cmd.Stdout = &outbuf
+	cmd.Stderr = &errbuf
+	err := cmd.Run()
+
+	stdout := strings.TrimSpace(outbuf.String())
+	stderr := strings.TrimSpace(errbuf.String())
+
+	if _, ok := err.(*exec.ExitError); ok {
+		return nil, fmt.Errorf("%s error: %s", command, stderr)
+	}
+	return strings.Split(stdout, "\n"), nil
+}
+
+func zpool() ([]string, error) {
+	return run("zpool", []string{"list", "-Hp"}...)
+}
+
+func sysctl(metric string) ([]string, error) {
+	return run("sysctl", []string{"-q", fmt.Sprintf("kstat.zfs.misc.%s", metric)}...)
+}
+
+func init() {
+	inputs.Add("zfs", func() telegraf.Input {
+		return &Zfs{
+			sysctl: sysctl,
+			zpool:  zpool,
+		}
+	})
+}