Added Unix epoch timestamp support for JSON parser

docs/DATA_FORMATS_INPUT.md

@@ -131,6 +131,12 @@ config "json_time_key" and "json_time_format". If "json_time_key" is set,
 "json_time_format" must be specified.  The "json_time_key" describes the
 name of the field containing time information.  The "json_time_format"
 must be a recognized Go time format.
+If parsing a Unix epoch timestamp in seconds, e.g. 1536092344.1, this config must be set to "unix" (case insensitive);
+corresponding JSON value can have a decimal part and can be a string or a number JSON representation.
+If value is in number representation, it'll be treated as a double precision float, and could have some precision loss.
+If value is in string representation, there'll be no precision loss up to nanosecond precision. Decimal positions beyond that will be dropped.
+If parsing a Unix epoch timestamp in milliseconds, e.g. 1536092344100, this config must be set to "unix_ms" (case insensitive);
+corresponding JSON value must be a (long) integer and be in number JSON representation.
 If there is no year provided, the metrics will have the current year.
 More info on time formats can be found here: https://golang.org/pkg/time/#Parse
 

plugins/parsers/json/parser.go

@@ -11,7 +11,10 @@ import (
 
 	"github.com/influxdata/telegraf"
 	"github.com/influxdata/telegraf/metric"
+	"github.com/pkg/errors"
 	"github.com/tidwall/gjson"
+	"math"
+	"regexp"
 )
 
 var (
@@ -47,6 +50,49 @@ func (p *JSONParser) parseArray(buf []byte) ([]telegraf.Metric, error) {
 	return metrics, nil
 }
 
+// format = "unix": epoch is assumed to be in seconds and can come as number or string. Can have a decimal part.
+// format = "unix_ms": epoch is assumed to be in milliseconds and can come as number or string. Cannot have a decimal part.
+func parseUnixTimestamp(jsonValue interface{}, format string) (time.Time, error) {
+	timeInt, timeFractional := int64(0), int64(0)
+	timeEpochStr, ok := jsonValue.(string)
+	var err error
+
+	if !ok {
+		timeEpochFloat, ok := jsonValue.(float64)
+		if !ok {
+			err := fmt.Errorf("time: %v could not be converted to string nor float64", jsonValue)
+			return time.Time{}, err
+		}
+		intPart, frac := math.Modf(timeEpochFloat)
+		timeInt, timeFractional = int64(intPart), int64(frac*1e9)
+	} else {
+		splitted := regexp.MustCompile("[.,]").Split(timeEpochStr, 2)
+		timeInt, err = strconv.ParseInt(splitted[0], 10, 64)
+		if err != nil {
+			return time.Time{}, err
+		}
+
+		if len(splitted) == 2 {
+			if len(splitted[1]) > 9 {
+				splitted[1] = splitted[1][:9] //truncates decimal part to nanoseconds precision
+			}
+			nanosecStr := splitted[1] + strings.Repeat("0", 9-len(splitted[1])) //adds 0's to the right to obtain a valid number of nanoseconds
+
+			timeFractional, err = strconv.ParseInt(nanosecStr, 10, 64)
+			if err != nil {
+				return time.Time{}, err
+			}
+		}
+	}
+	if strings.EqualFold(format, "unix") {
+		return time.Unix(timeInt, timeFractional).UTC(), nil
+	} else if strings.EqualFold(format, "unix_ms") {
+		return time.Unix(timeInt/1000, (timeInt%1000)*1e6).UTC(), nil
+	} else {
+		return time.Time{}, errors.New("Invalid unix format")
+	}
+}
+
 func (p *JSONParser) parseObject(metrics []telegraf.Metric, jsonOut map[string]interface{}) ([]telegraf.Metric, error) {
 
 	tags := make(map[string]string)
@@ -78,14 +124,21 @@ func (p *JSONParser) parseObject(metrics []telegraf.Metric, jsonOut map[string]i
 			return nil, err
 		}
 
-		timeStr, ok := f.Fields[p.JSONTimeKey].(string)
-		if !ok {
-			err := fmt.Errorf("time: %v could not be converted to string", f.Fields[p.JSONTimeKey])
-			return nil, err
-		}
-		nTime, err = time.Parse(p.JSONTimeFormat, timeStr)
-		if err != nil {
-			return nil, err
+		if strings.EqualFold(p.JSONTimeFormat, "unix") || strings.EqualFold(p.JSONTimeFormat, "unix_ms") {
+			nTime, err = parseUnixTimestamp(f.Fields[p.JSONTimeKey], p.JSONTimeFormat)
+			if err != nil {
+				return nil, err
+			}
+		} else {
+			timeStr, ok := f.Fields[p.JSONTimeKey].(string)
+			if !ok {
+				err := fmt.Errorf("time: %v could not be converted to string", f.Fields[p.JSONTimeKey])
+				return nil, err
+			}
+			nTime, err = time.Parse(p.JSONTimeFormat, timeStr)
+			if err != nil {
+				return nil, err
+			}
 		}
 
 		//if the year is 0, set to current year

plugins/parsers/json/parser_test.go

@@ -596,6 +596,72 @@ func TestTimeParser(t *testing.T) {
 	require.Equal(t, false, metrics[0].Time() == metrics[1].Time())
 }
 
+func TestUnixTimeParser(t *testing.T) {
+	testString := `[
+		{
+			"a": 5,
+			"b": {
+				"c": 6,
+				"time": "1536001411.1234567890"
+			},
+			"my_tag_1": "foo",
+			"my_tag_2": "baz"
+		},
+		{
+			"a": 7,
+			"b": {
+				"c": 8,
+				"time": 1536002769.123
+			},
+			"my_tag_1": "bar",
+			"my_tag_2": "baz"
+		}
+	]`
+
+	parser := JSONParser{
+		MetricName:     "json_test",
+		JSONTimeKey:    "b_time",
+		JSONTimeFormat: "unix",
+	}
+	metrics, err := parser.Parse([]byte(testString))
+	require.NoError(t, err)
+	require.Equal(t, 2, len(metrics))
+	require.Equal(t, false, metrics[0].Time() == metrics[1].Time())
+}
+
+func TestUnixMsTimeParser(t *testing.T) {
+	testString := `[
+		{
+			"a": 5,
+			"b": {
+				"c": 6,
+				"time": "1536001411100"
+			},
+			"my_tag_1": "foo",
+			"my_tag_2": "baz"
+		},
+		{
+			"a": 7,
+			"b": {
+				"c": 8,
+				"time": 1536002769123
+			},
+			"my_tag_1": "bar",
+			"my_tag_2": "baz"
+		}
+	]`
+
+	parser := JSONParser{
+		MetricName:     "json_test",
+		JSONTimeKey:    "b_time",
+		JSONTimeFormat: "unix_ms",
+	}
+	metrics, err := parser.Parse([]byte(testString))
+	require.NoError(t, err)
+	require.Equal(t, 2, len(metrics))
+	require.Equal(t, false, metrics[0].Time() == metrics[1].Time())
+}
+
 func TestTimeErrors(t *testing.T) {
 	testString := `{
 		"a": 5,