Ignore errors serializing single metrics (#5943)

plugins/serializers/influx/influx.go

@@ -113,6 +113,9 @@ func (s *Serializer) SerializeBatch(metrics []telegraf.Metric) ([]byte, error) {
 	for _, m := range metrics {
 		_, err := s.Write(&s.buf, m)
 		if err != nil {
+			if _, ok := err.(*MetricError); ok {
+				continue
+			}
 			return nil, err
 		}
 	}

plugins/serializers/influx/reader.go

@@ -53,12 +53,13 @@ func (r *reader) Read(p []byte) (int, error) {
 		r.offset += 1
 		if err != nil {
 			r.buf.Reset()
-			if err != nil {
-				// Since we are serializing multiple metrics, don't fail the
-				// the entire batch just because of one unserializable metric.
-				log.Printf("E! [serializers.influx] could not serialize metric: %v; discarding metric", err)
+			if _, ok := err.(*MetricError); ok {
 				continue
 			}
+			// Since we are serializing multiple metrics, don't fail the
+			// the entire batch just because of one unserializable metric.
+			log.Printf("E! [serializers.influx] could not serialize metric: %v; discarding metric", err)
+			continue
 		}
 		break
 	}

plugins/serializers/registry.go

@@ -30,6 +30,9 @@ type Serializer interface {
 	// Serialize takes a single telegraf metric and turns it into a byte buffer.
 	// separate metrics should be separated by a newline, and there should be
 	// a newline at the end of the buffer.
+	//
+	// New plugins should use SerializeBatch instead to allow for non-line
+	// delimited metrics.
 	Serialize(metric telegraf.Metric) ([]byte, error)
 
 	// SerializeBatch takes an array of telegraf metric and serializes it into
@@ -41,7 +44,7 @@ type Serializer interface {
 // Config is a struct that covers the data types needed for all serializer types,
 // and can be used to instantiate _any_ of the serializers.
 type Config struct {
-	// Dataformat can be one of: influx, graphite, or json
+	// Dataformat can be one of the serializer types listed in NewSerializer.
 	DataFormat string
 
 	// Support tags in graphite protocol