Remove the time_key from the field values in JSON parser (#4951)

plugins/parsers/json/parser.go

@@ -143,6 +143,8 @@ func (p *JSONParser) parseObject(metrics []telegraf.Metric, jsonOut map[string]i
 			}
 		}
 
+		delete(f.Fields, p.JSONTimeKey)
+
 		//if the year is 0, set to current year
 		if nTime.Year() == 0 {
 			nTime = nTime.AddDate(time.Now().Year(), 0, 0)

plugins/parsers/json/parser_test.go

@@ -4,7 +4,10 @@ import (
 	"fmt"
 	"log"
 	"testing"
+	"time"
 
+	"github.com/influxdata/telegraf"
+	"github.com/influxdata/telegraf/testutil"
 	"github.com/stretchr/testify/require"
 )
 
@@ -724,3 +727,27 @@ func TestNameKey(t *testing.T) {
 	require.NoError(t, err)
 	require.Equal(t, "this is my name", metrics[0].Name())
 }
+
+func TestTimeKeyDelete(t *testing.T) {
+	data := `{
+		"timestamp": 1541183052,
+		"value": 42
+	}`
+
+	parser := JSONParser{
+		MetricName:     "json",
+		JSONTimeKey:    "timestamp",
+		JSONTimeFormat: "unix",
+	}
+
+	metrics, err := parser.Parse([]byte(data))
+	require.NoError(t, err)
+	expected := []telegraf.Metric{
+		testutil.MustMetric("json",
+			map[string]string{},
+			map[string]interface{}{"value": 42.0},
+			time.Unix(1541183052, 0)),
+	}
+
+	testutil.RequireMetricsEqual(t, expected, metrics)
+}