Terminate exporter when file cannot be opened

main.go

@@ -24,12 +24,12 @@ import (
 	"os/signal"
 	"syscall"
 
-	"github.com/hpcloud/tail"
 	"github.com/martin-helmich/prometheus-nginxlog-exporter/config"
 	"github.com/martin-helmich/prometheus-nginxlog-exporter/discovery"
 	"github.com/prometheus/client_golang/prometheus"
 	"github.com/satyrius/gonx"
 	"github.com/martin-helmich/prometheus-nginxlog-exporter/relabeling"
+	"github.com/martin-helmich/prometheus-nginxlog-exporter/tail"
 )
 
 // Metrics is a struct containing pointers to all metrics that should be
@@ -169,15 +169,15 @@ func main() {
 			metrics.Init(&nsCfg)
 
 			for _, f := range nsCfg.SourceFiles {
-				t, err := tail.TailFile(f, tail.Config{
-					Follow: true,
-					ReOpen: true,
-					Poll:   true,
-				})
+				t, err := tail.NewFollower(f)
 				if err != nil {
 					panic(err)
 				}
 
+				t.OnError(func (err error) {
+					panic(err)
+				})
+
 				go func(nsCfg config.NamespaceConfig) {
 					relabelings := relabeling.NewRelabelings(nsCfg.RelabelConfigs)
 					relabelings = append(relabeling.DefaultRelabelings, relabelings...)
@@ -192,7 +192,7 @@ func main() {
 						labelValues[i] = staticLabelValues[i]
 					}
 
-					for line := range t.Lines {
+					for line := range t.Lines() {
 						entry, err := parser.ParseString(line.Text)
 						if err != nil {
 							fmt.Printf("error while parsing line '%s': %s\n", line.Text, err)

tail/tailer.go

@@ -0,0 +1,55 @@
+package tail
+
+import (
+	"github.com/hpcloud/tail"
+)
+
+type Follower interface {
+	Lines() chan *tail.Line
+	OnError(func (error))
+}
+
+type followerImpl struct {
+	filename string
+	t *tail.Tail
+}
+
+func NewFollower(filename string) (Follower, error) {
+	f := &followerImpl{
+		filename: filename,
+	}
+
+	if err := f.start(); err != nil {
+		return nil, err
+	}
+
+	return f, nil
+}
+
+func (f *followerImpl) start() error {
+	t, err := tail.TailFile(f.filename, tail.Config{
+		Follow: true,
+		ReOpen: true,
+		Poll:   true,
+	})
+
+	if err != nil {
+		return err
+	}
+
+	f.t = t
+	return nil
+}
+
+func (f *followerImpl) OnError(cb func(error)) {
+	go func() {
+		err := f.t.Wait()
+		if err != nil {
+			cb(err)
+		}
+	}()
+}
+
+func (f *followerImpl) Lines() chan *tail.Line {
+	return f.t.Lines
+}