Adds a new json_timestamp_units configuration parameter (#2587)

docs/DATA_FORMATS_OUTPUT.md

@@ -147,4 +147,14 @@ The JSON data format serialized Telegraf metrics in json format. The format is:
   ## more about them here:
   ## https://github.com/influxdata/telegraf/blob/master/docs/DATA_FORMATS_OUTPUT.md
   data_format = "json"
+  json_timestamp_units = "1ns"
 ```
+
+By default, the timestamp that is output in JSON data format serialized Telegraf
+metrics is in seconds. The precision of this timestamp can be adjusted for any output
+by adding the optional `json_timestamp_units` parameter to the configuration for
+that output. This parameter can be used to set the timestamp units to  nanoseconds (`ns`),
+microseconds (`us` or `µs`), milliseconds (`ms`), or seconds (`s`). Note that this
+parameter will be truncated to the nearest power of 10 that, so if the `json_timestamp_units`
+are set to `15ms` the timestamps for the JSON format serialized Telegraf metrics will be
+output in hundredths of a second (`10ms`).

internal/config/config.go

@@ -6,6 +6,7 @@ import (
 	"fmt"
 	"io/ioutil"
 	"log"
+	"math"
 	"os"
 	"path/filepath"
 	"regexp"
@@ -1244,7 +1245,7 @@ func buildParser(name string, tbl *ast.Table) (parsers.Parser, error) {
 // a serializers.Serializer object, and creates it, which can then be added onto
 // an Output object.
 func buildSerializer(name string, tbl *ast.Table) (serializers.Serializer, error) {
-	c := &serializers.Config{}
+	c := &serializers.Config{TimestampUnits: time.Duration(1 * time.Second)}
 
 	if node, ok := tbl.Fields["data_format"]; ok {
 		if kv, ok := node.(*ast.KeyValue); ok {
@@ -1274,9 +1275,26 @@ func buildSerializer(name string, tbl *ast.Table) (serializers.Serializer, error
 		}
 	}
 
+	if node, ok := tbl.Fields["json_timestamp_units"]; ok {
+		if kv, ok := node.(*ast.KeyValue); ok {
+			if str, ok := kv.Value.(*ast.String); ok {
+				timestampVal, err := time.ParseDuration(str.Value)
+				if err != nil {
+					return nil, fmt.Errorf("Unable to parse json_timestamp_units as a duration, %s", err)
+				}
+				// now that we have a duration, truncate it to the nearest
+				// power of ten (just in case)
+				nearest_exponent := int64(math.Log10(float64(timestampVal.Nanoseconds())))
+				new_nanoseconds := int64(math.Pow(10.0, float64(nearest_exponent)))
+				c.TimestampUnits = time.Duration(new_nanoseconds)
+			}
+		}
+	}
+
 	delete(tbl.Fields, "data_format")
 	delete(tbl.Fields, "prefix")
 	delete(tbl.Fields, "template")
+	delete(tbl.Fields, "json_timestamp_units")
 	return serializers.NewSerializer(c)
 }
 

plugins/serializers/json/json.go

@@ -2,19 +2,27 @@ package json
 
 import (
 	ejson "encoding/json"
+	"time"
 
 	"github.com/influxdata/telegraf"
 )
 
 type JsonSerializer struct {
+	TimestampUnits time.Duration
 }
 
 func (s *JsonSerializer) Serialize(metric telegraf.Metric) ([]byte, error) {
 	m := make(map[string]interface{})
+	units_nanoseconds := s.TimestampUnits.Nanoseconds()
+	// if the units passed in were less than or equal to zero,
+	// then serialize the timestamp in seconds (the default)
+	if units_nanoseconds <= 0 {
+		units_nanoseconds = 1000000000
+	}
 	m["tags"] = metric.Tags()
 	m["fields"] = metric.Fields()
 	m["name"] = metric.Name()
-	m["timestamp"] = metric.UnixNano() / 1000000000
+	m["timestamp"] = metric.UnixNano() / units_nanoseconds
 	serialized, err := ejson.Marshal(m)
 	if err != nil {
 		return []byte{}, err

plugins/serializers/registry.go

@@ -2,6 +2,7 @@ package serializers
 
 import (
 	"fmt"
+	"time"
 
 	"github.com/influxdata/telegraf"
 
@@ -29,7 +30,7 @@ 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
+	// Dataformat can be one of: influx, graphite, or json
 	DataFormat string
 
 	// Prefix to add to all measurements, only supports Graphite
@@ -38,6 +39,9 @@ type Config struct {
 	// Template for converting telegraf metrics into Graphite
 	// only supports Graphite
 	Template string
+
+	// Timestamp units to use for JSON formatted output
+	TimestampUnits time.Duration
 }
 
 // NewSerializer a Serializer interface based on the given config.
@@ -50,15 +54,15 @@ func NewSerializer(config *Config) (Serializer, error) {
 	case "graphite":
 		serializer, err = NewGraphiteSerializer(config.Prefix, config.Template)
 	case "json":
-		serializer, err = NewJsonSerializer()
+		serializer, err = NewJsonSerializer(config.TimestampUnits)
 	default:
 		err = fmt.Errorf("Invalid data format: %s", config.DataFormat)
 	}
 	return serializer, err
 }
 
-func NewJsonSerializer() (Serializer, error) {
-	return &json.JsonSerializer{}, nil
+func NewJsonSerializer(timestampUnits time.Duration) (Serializer, error) {
+	return &json.JsonSerializer{TimestampUnits: timestampUnits}, nil
 }
 
 func NewInfluxSerializer() (Serializer, error) {