metric: Fix negative number handling

closes #2324

plugins/parsers/influx/parser_test.go

@@ -19,6 +19,7 @@ var (
 
 const (
 	validInflux          = "cpu_load_short,cpu=cpu0 value=10 1257894000000000000\n"
+	negativeFloat        = "cpu_load_short,cpu=cpu0 value=-13.4 1257894000000000000\n"
 	validInfluxNewline   = "\ncpu_load_short,cpu=cpu0 value=10 1257894000000000000\n"
 	validInfluxNoNewline = "cpu_load_short,cpu=cpu0 value=10 1257894000000000000"
 	invalidInflux        = "I don't think this is line protocol\n"
@@ -82,6 +83,18 @@ func TestParseValidInflux(t *testing.T) {
 		"cpu": "cpu0",
 	}, metrics[0].Tags())
 	assert.Equal(t, exptime, metrics[0].Time().UnixNano())
+
+	metrics, err = parser.Parse([]byte(negativeFloat))
+	assert.NoError(t, err)
+	assert.Len(t, metrics, 1)
+	assert.Equal(t, "cpu_load_short", metrics[0].Name())
+	assert.Equal(t, map[string]interface{}{
+		"value": float64(-13.4),
+	}, metrics[0].Fields())
+	assert.Equal(t, map[string]string{
+		"cpu": "cpu0",
+	}, metrics[0].Tags())
+	assert.Equal(t, exptime, metrics[0].Time().UnixNano())
 }
 
 func TestParseLineValidInflux(t *testing.T) {