diff --git a/client/operation.go b/client/operation.go
index b0a6870..228b6e1 100644
--- a/client/operation.go
+++ b/client/operation.go
@@ -250,19 +250,28 @@ func (hc *houstonClient) launch(meta *procmeta) error {
 			}
 
 			if readingMetric {
+				logger.Println("readingMetric is on :", string(buff))
 				if metricBuffer[len(metricBuffer)-2] == metric.METRIC_TAIL_INLINE {
 					readingMetric = false
+					logger.Println("readingMetric is off :", string(buff))
 
 					metricBuffer = metricBuffer[:len(metricBuffer)-2]
 					if metricBuffer[0] == '{' {
 						var metric metric.MetricDescription
-						json.Unmarshal(metricBuffer, &metric)
+						if err := json.Unmarshal(metricBuffer, &metric); err != nil {
+							logger.Println("unmarshal metric failed :", err, string(metricBuffer))
+							continue
+						}
 
-						exporter := newExporterForPrometheus()
-						accessor := exporter.registMetric(childProcName, metric)
-						prometheus.MustRegister(exporter)
+						if _, registered := metricValues[metric.Key]; !registered {
+							exporter := newExporterForPrometheus()
+							accessor := exporter.registMetric(childProcName, metric)
 
-						metricValues[metric.Key] = accessor
+							prometheus.Register(exporter)
+
+							metricValues[metric.Key] = accessor
+							logger.Println("metric registered :", metric)
+						}
 					} else {
 						keybytes := metricBuffer[:8]
 						valbits := binary.BigEndian.Uint64(metricBuffer[8:])