Fixed registrar stats for beats >= 6.3

* Previously registrar stats writes didn't have subdivisions
  of fail, success and total. In newer version of beats they
  do, adding support for the same.
* Also adding error details on a log line to help in debugging in
  case of an issue

VERSION

@@ -1 +1 @@
-0.1.0
+0.1.1

collector/main.go

@@ -92,7 +92,7 @@ func (b *mainCollector) Collect(ch chan<- prometheus.Metric) {
 	err := b.fetchStatsEndpoint()
 	if err != nil {
 		ch <- prometheus.MustNewConstMetric(b.targetUp, prometheus.GaugeValue, float64(0)) // set target down
-		log.Errorf("Failed getting /stats endpoint of target")
+		log.Errorf("Failed getting /stats endpoint of target: " + err.Error())
 		return
 	}
 

collector/registrar.go

@@ -6,7 +6,11 @@ import (
 
 //Registrar json structure
 type Registrar struct {
-	Writes float64 `json:"writes"`
+	Writes struct {
+		Fail    float64 `json:"fail"`
+		Success float64 `json:"success"`
+		Total   float64 `json:"total"`
+	} `json:"writes"`
 	States struct {
 		Cleanup float64 `json:"cleanup"`
 		Current float64 `json:"current"`
@@ -30,10 +34,28 @@ func NewRegistrarCollector(beatInfo *BeatInfo, stats *Stats) prometheus.Collecto
 				desc: prometheus.NewDesc(
 					prometheus.BuildFQName(beatInfo.Beat, "registrar", "writes"),
 					"registrar.writes",
-					nil, nil,
+					nil, prometheus.Labels{"writes": "fail"},
 				),
-				eval:    func(stats *Stats) float64 { return stats.Registrar.Writes },
-				valType: prometheus.CounterValue,
+				eval:    func(stats *Stats) float64 { return stats.Registrar.Writes.Fail },
+				valType: prometheus.GaugeValue,
+			},
+			{
+				desc: prometheus.NewDesc(
+					prometheus.BuildFQName(beatInfo.Beat, "registrar", "writes"),
+					"registrar.writes",
+					nil, prometheus.Labels{"writes": "success"},
+				),
+				eval:    func(stats *Stats) float64 { return stats.Registrar.Writes.Success },
+				valType: prometheus.GaugeValue,
+			},
+			{
+				desc: prometheus.NewDesc(
+					prometheus.BuildFQName(beatInfo.Beat, "registrar", "writes"),
+					"registrar.writes",
+					nil, prometheus.Labels{"writes": "total"},
+				),
+				eval:    func(stats *Stats) float64 { return stats.Registrar.Writes.Total },
+				valType: prometheus.GaugeValue,
 			},
 			{
 				desc: prometheus.NewDesc(