Ignore fields with NaN or Inf floats in the JSON serializer (#7426)

plugins/serializers/json/json.go

@@ -2,6 +2,7 @@ package json
 
 import (
 	"encoding/json"
+	"math"
 	"time"
 
 	"github.com/influxdata/telegraf"
@@ -49,8 +50,26 @@ func (s *serializer) SerializeBatch(metrics []telegraf.Metric) ([]byte, error) {
 
 func (s *serializer) createObject(metric telegraf.Metric) map[string]interface{} {
 	m := make(map[string]interface{}, 4)
-	m["tags"] = metric.Tags()
-	m["fields"] = metric.Fields()
+
+	tags := make(map[string]string, len(metric.TagList()))
+	for _, tag := range metric.TagList() {
+		tags[tag.Key] = tag.Value
+	}
+	m["tags"] = tags
+
+	fields := make(map[string]interface{}, len(metric.FieldList()))
+	for _, field := range metric.FieldList() {
+		switch fv := field.Value.(type) {
+		case float64:
+			// JSON does not support these special values
+			if math.IsNaN(fv) || math.IsInf(fv, 0) {
+				continue
+			}
+		}
+		fields[field.Key] = field.Value
+	}
+	m["fields"] = fields
+
 	m["name"] = metric.Name()
 	m["timestamp"] = metric.Time().UnixNano() / int64(s.TimestampUnits)
 	return m

plugins/serializers/json/json_test.go

@@ -2,14 +2,15 @@ package json
 
 import (
 	"fmt"
+	"math"
 	"testing"
 	"time"
 
-	"github.com/stretchr/testify/assert"
-	"github.com/stretchr/testify/require"
-
 	"github.com/influxdata/telegraf"
 	"github.com/influxdata/telegraf/metric"
+	"github.com/influxdata/telegraf/testutil"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
 )
 
 func MustMetric(v telegraf.Metric, err error) telegraf.Metric {
@@ -193,3 +194,42 @@ func TestSerializeBatch(t *testing.T) {
 	require.NoError(t, err)
 	require.Equal(t, []byte(`{"metrics":[{"fields":{"value":42},"name":"cpu","tags":{},"timestamp":0},{"fields":{"value":42},"name":"cpu","tags":{},"timestamp":0}]}`), buf)
 }
+
+func TestSerializeBatchSkipInf(t *testing.T) {
+	metrics := []telegraf.Metric{
+		testutil.MustMetric(
+			"cpu",
+			map[string]string{},
+			map[string]interface{}{
+				"inf":       math.Inf(1),
+				"time_idle": 42,
+			},
+			time.Unix(0, 0),
+		),
+	}
+
+	s, err := NewSerializer(0)
+	require.NoError(t, err)
+	buf, err := s.SerializeBatch(metrics)
+	require.NoError(t, err)
+	require.Equal(t, []byte(`{"metrics":[{"fields":{"time_idle":42},"name":"cpu","tags":{},"timestamp":0}]}`), buf)
+}
+
+func TestSerializeBatchSkipInfAllFields(t *testing.T) {
+	metrics := []telegraf.Metric{
+		testutil.MustMetric(
+			"cpu",
+			map[string]string{},
+			map[string]interface{}{
+				"inf": math.Inf(1),
+			},
+			time.Unix(0, 0),
+		),
+	}
+
+	s, err := NewSerializer(0)
+	require.NoError(t, err)
+	buf, err := s.SerializeBatch(metrics)
+	require.NoError(t, err)
+	require.Equal(t, []byte(`{"metrics":[{"fields":{},"name":"cpu","tags":{},"timestamp":0}]}`), buf)
+}