From f51b1f882d9e785172120ea864497b6878a4bfaf Mon Sep 17 00:00:00 2001
From: Bart Vercoulen <bartv@kumina.nl>
Date: Mon, 17 Dec 2018 17:01:01 +0100
Subject: [PATCH] Refactored to kingpin and fixed a EOF bug in
 CollectShowqFromReader.

---
 nosystemd.go        |  9 +++++++--
 postfix_exporter.go | 21 +++++++++++----------
 systemd.go          | 12 ++++++------
 3 files changed, 24 insertions(+), 18 deletions(-)

diff --git a/nosystemd.go b/nosystemd.go
index cfbffce..33c1a16 100644
--- a/nosystemd.go
+++ b/nosystemd.go
@@ -3,14 +3,19 @@
 
 package main
 
-import "io"
+import(
+	"io"
+
+	"github.com/alecthomas/kingpin"
+)
+
 
 type Journal struct {
 	io.Closer
 	Path string
 }
 
-func systemdFlags(enable *bool, unit, slice, path *string) {}
+func systemdFlags(enable *bool, unit, slice, path *string, app *kingpin.Application) {}
 
 func NewJournal(unit, slice, path string) (*Journal, error) {
 	return nil, nil
diff --git a/postfix_exporter.go b/postfix_exporter.go
index adcac92..b853209 100644
--- a/postfix_exporter.go
+++ b/postfix_exporter.go
@@ -17,8 +17,8 @@ import (
 	"bufio"
 	"bytes"
 	"errors"
-	"flag"
 	"fmt"
+	"github.com/alecthomas/kingpin"
 	"io"
 	"log"
 	"net"
@@ -78,7 +78,7 @@ type PostfixExporter struct {
 func CollectShowqFromReader(file io.Reader, ch chan<- prometheus.Metric) error {
 	reader := bufio.NewReader(file)
 	buf, err := reader.Peek(128)
-	if err != nil {
+	if err != nil && err != io.EOF {
 		log.Printf("Could not read postfix output, %v", err)
 	}
 	if bytes.IndexByte(buf, 0) >= 0 {
@@ -663,16 +663,17 @@ func (e *PostfixExporter) Collect(ch chan<- prometheus.Metric) {
 
 func main() {
 	var (
-		listenAddress      = flag.String("web.listen-address", ":9154", "Address to listen on for web interface and telemetry.")
-		metricsPath        = flag.String("web.telemetry-path", "/metrics", "Path under which to expose metrics.")
-		postfixShowqPath   = flag.String("postfix.showq_path", "/var/spool/postfix/public/showq", "Path at which Postfix places its showq socket.")
-		postfixLogfilePath = flag.String("postfix.logfile_path", "/var/log/postfix_exporter_input.log", "Path where Postfix writes log entries. This file will be truncated by this exporter.")
-
-		systemdEnable                                 bool
+		app					= kingpin.New("postfix_exporter", "Prometheus metrics exporter for postfix")
+		listenAddress 		= app.Flag("web.listen-address", "Address to listen on for web interface and telemetry.").Default(":9154").String()
+		metricsPath   		= app.Flag("web.telemetry-path", "Path under which to expose metrics.").Default("/metrics").String()
+		postfixShowqPath    = app.Flag("postfix.showq_path", "Path at which Postfix places its showq socket.").Default("/var/spool/postfix/public/showq").String()
+		postfixLogfilePath	= app.Flag("postfix.logfile_path", "Path where Postfix writes log entries. This file will be truncated by this exporter.").Default("/var/log/postfix_exporter_input.log").String()
+		systemdEnable bool
 		systemdUnit, systemdSlice, systemdJournalPath string
 	)
-	systemdFlags(&systemdEnable, &systemdUnit, &systemdSlice, &systemdJournalPath)
-	flag.Parse()
+	systemdFlags(&systemdEnable, &systemdUnit, &systemdSlice, &systemdJournalPath, app)
+
+	kingpin.MustParse(app.Parse(os.Args[1:]))
 
 	var journal *Journal
 	if systemdEnable {
diff --git a/systemd.go b/systemd.go
index 9a78ff8..d9d02f7 100644
--- a/systemd.go
+++ b/systemd.go
@@ -3,12 +3,12 @@
 package main
 
 import (
-	"flag"
 	"fmt"
 	"log"
 	"sync"
 	"time"
 
+	"github.com/alecthomas/kingpin"
 	"github.com/coreos/go-systemd/sdjournal"
 )
 
@@ -88,11 +88,11 @@ func (j *Journal) NextMessage() (s string, c uint64, err error) {
 }
 
 // systemdFlags sets the flags for use with systemd
-func systemdFlags(enable *bool, unit, slice, path *string) {
-	flag.BoolVar(enable, "systemd.enable", false, "Read from the systemd journal instead of log")
-	flag.StringVar(unit, "systemd.unit", "postfix.service", "Name of the Postfix systemd unit.")
-	flag.StringVar(slice, "systemd.slice", "", "Name of the Postfix systemd slice. Overrides the systemd unit.")
-	flag.StringVar(path, "systemd.journal_path", "", "Path to the systemd journal")
+func systemdFlags(enable *bool, unit, slice, path *string, app *kingpin.Application) {
+	app.Flag("systemd.enable", "Read from the systemd journal instead of log").Default("false").BoolVar(enable)
+	app.Flag("systemd.unit", "Name of the Postfix systemd unit.").Default("postfix.service").StringVar(unit)
+	app.Flag("systemd.slice", "Name of the Postfix systemd slice. Overrides the systemd unit.").Default("").StringVar(slice)
+	app.Flag("systemd.journal_path", "Path to the systemd journal").Default("").StringVar(path)
 }
 
 // CollectLogfileFromJournal Collects entries from the systemd journal.