Add postfix input plugin (#2553)

plugins/inputs/postfix/postfix.go

@@ -0,0 +1,119 @@
+package postfix
+
+import (
+	"fmt"
+	"os"
+	"os/exec"
+	"path"
+	"strings"
+	"time"
+
+	"github.com/influxdata/telegraf"
+	"github.com/influxdata/telegraf/plugins/inputs"
+)
+
+const sampleConfig = `
+  ## Postfix queue directory. If not provided, telegraf will try to use
+  ## 'postconf -h queue_directory' to determine it.
+  # queue_directory = "/var/spool/postfix"
+`
+
+const description = "Measure postfix queue statistics"
+
+func getQueueDirectory() (string, error) {
+	qd, err := exec.Command("postconf", "-h", "queue_directory").Output()
+	if err != nil {
+		return "", err
+	}
+	return strings.TrimSpace(string(qd)), nil
+}
+
+func qScan(path string) (int64, int64, int64, error) {
+	f, err := os.Open(path)
+	if err != nil {
+		return 0, 0, 0, err
+	}
+
+	finfos, err := f.Readdir(-1)
+	f.Close()
+	if err != nil {
+		return 0, 0, 0, err
+	}
+
+	var length, size int64
+	var oldest time.Time
+	for _, finfo := range finfos {
+		length++
+		size += finfo.Size()
+		if oldest.IsZero() || finfo.ModTime().Before(oldest) {
+			oldest = finfo.ModTime()
+		}
+	}
+	var age time.Duration
+	if !oldest.IsZero() {
+		age = time.Now().Sub(oldest) / time.Second
+	}
+	return length, size, int64(age), nil
+}
+
+type Postfix struct {
+	QueueDirectory string
+}
+
+func (p *Postfix) Gather(acc telegraf.Accumulator) error {
+	if p.QueueDirectory == "" {
+		var err error
+		p.QueueDirectory, err = getQueueDirectory()
+		if err != nil {
+			return fmt.Errorf("unable to determine queue directory: %s", err)
+		}
+	}
+
+	for _, q := range []string{"active", "hold", "incoming", "maildrop"} {
+		length, size, age, err := qScan(path.Join(p.QueueDirectory, q))
+		if err != nil {
+			acc.AddError(fmt.Errorf("error scanning queue %s: %s", q, err))
+			continue
+		}
+		fields := map[string]interface{}{"length": length, "size": size, "age": age}
+		acc.AddFields("postfix_queue", fields, map[string]string{"queue": q})
+	}
+
+	var dLength, dSize, dAge int64
+	for _, q := range []string{"0", "1", "2", "3", "4", "5", "6", "7", "8", "9", "A", "B", "C", "D", "E", "F"} {
+		length, size, age, err := qScan(path.Join(p.QueueDirectory, "deferred", q))
+		if err != nil {
+			if os.IsNotExist(err) {
+				// the directories are created on first use
+				continue
+			}
+			acc.AddError(fmt.Errorf("error scanning queue deferred/%s: %s", q, err))
+			return nil
+		}
+		dLength += length
+		dSize += size
+		if age > dAge {
+			dAge = age
+		}
+	}
+	fields := map[string]interface{}{"length": dLength, "size": dSize, "age": dAge}
+	acc.AddFields("postfix_queue", fields, map[string]string{"queue": "deferred"})
+
+	return nil
+}
+
+func (p *Postfix) SampleConfig() string {
+	return sampleConfig
+}
+
+func (p *Postfix) Description() string {
+	return description
+}
+
+func init() {
+	inputs.Add("postfix", func() telegraf.Input {
+		return &Postfix{
+			QueueDirectory: "/var/spool/postfix",
+		}
+	})
+}