Add prometheus serializer and use it in prometheus output (#6703)

plugins/serializers/registry.go

@@ -10,6 +10,7 @@ import (
 	"github.com/influxdata/telegraf/plugins/serializers/influx"
 	"github.com/influxdata/telegraf/plugins/serializers/json"
 	"github.com/influxdata/telegraf/plugins/serializers/nowmetric"
+	"github.com/influxdata/telegraf/plugins/serializers/prometheus"
 	"github.com/influxdata/telegraf/plugins/serializers/splunkmetric"
 	"github.com/influxdata/telegraf/plugins/serializers/wavefront"
 )
@@ -45,43 +46,54 @@ type Serializer interface {
 // and can be used to instantiate _any_ of the serializers.
 type Config struct {
 	// Dataformat can be one of the serializer types listed in NewSerializer.
-	DataFormat string
+	DataFormat string `toml:"data_format"`
 
 	// Support tags in graphite protocol
-	GraphiteTagSupport bool
+	GraphiteTagSupport bool `toml:"graphite_tag_support"`
 
 	// Maximum line length in bytes; influx format only
-	InfluxMaxLineBytes int
+	InfluxMaxLineBytes int `toml:"influx_max_line_bytes"`
 
 	// Sort field keys, set to true only when debugging as it less performant
 	// than unsorted fields; influx format only
-	InfluxSortFields bool
+	InfluxSortFields bool `toml:"influx_sort_fields"`
 
 	// Support unsigned integer output; influx format only
-	InfluxUintSupport bool
+	InfluxUintSupport bool `toml:"influx_uint_support"`
 
 	// Prefix to add to all measurements, only supports Graphite
-	Prefix string
+	Prefix string `toml:"prefix"`
 
 	// Template for converting telegraf metrics into Graphite
 	// only supports Graphite
-	Template string
+	Template string `toml:"template"`
 
 	// Timestamp units to use for JSON formatted output
-	TimestampUnits time.Duration
+	TimestampUnits time.Duration `toml:"timestamp_units"`
 
 	// Include HEC routing fields for splunkmetric output
-	HecRouting bool
+	HecRouting bool `toml:"hec_routing"`
 
 	// Enable Splunk MultiMetric output (Splunk 8.0+)
-	SplunkmetricMultiMetric bool
+	SplunkmetricMultiMetric bool `toml:"splunkmetric_multi_metric"`
 
 	// Point tags to use as the source name for Wavefront (if none found, host will be used).
-	WavefrontSourceOverride []string
+	WavefrontSourceOverride []string `toml:"wavefront_source_override"`
 
 	// Use Strict rules to sanitize metric and tag names from invalid characters for Wavefront
 	// When enabled forward slash (/) and comma (,) will be accepted
-	WavefrontUseStrict bool
+	WavefrontUseStrict bool `toml:"wavefront_use_strict"`
+
+	// Include the metric timestamp on each sample.
+	PrometheusExportTimestamp bool `toml:"prometheus_export_timestamp"`
+
+	// Sort prometheus metric families and metric samples.  Useful for
+	// debugging.
+	PrometheusSortMetrics bool `toml:"prometheus_sort_metrics"`
+
+	// Output string fields as metric labels; when false string fields are
+	// discarded.
+	PrometheusStringAsLabel bool `toml:"prometheus_string_as_label"`
 }
 
 // NewSerializer a Serializer interface based on the given config.
@@ -103,12 +115,37 @@ func NewSerializer(config *Config) (Serializer, error) {
 		serializer, err = NewCarbon2Serializer()
 	case "wavefront":
 		serializer, err = NewWavefrontSerializer(config.Prefix, config.WavefrontUseStrict, config.WavefrontSourceOverride)
+	case "prometheus":
+		serializer, err = NewPrometheusSerializer(config)
 	default:
 		err = fmt.Errorf("Invalid data format: %s", config.DataFormat)
 	}
 	return serializer, err
 }
 
+func NewPrometheusSerializer(config *Config) (Serializer, error) {
+	exportTimestamp := prometheus.NoExportTimestamp
+	if config.PrometheusExportTimestamp {
+		exportTimestamp = prometheus.ExportTimestamp
+	}
+
+	sortMetrics := prometheus.NoSortMetrics
+	if config.PrometheusExportTimestamp {
+		sortMetrics = prometheus.SortMetrics
+	}
+
+	stringAsLabels := prometheus.DiscardStrings
+	if config.PrometheusStringAsLabel {
+		stringAsLabels = prometheus.StringAsLabel
+	}
+
+	return prometheus.NewSerializer(prometheus.FormatConfig{
+		TimestampExport: exportTimestamp,
+		MetricSortOrder: sortMetrics,
+		StringHandling:  stringAsLabels,
+	})
+}
+
 func NewWavefrontSerializer(prefix string, useStrict bool, sourceOverride []string) (Serializer, error) {
 	return wavefront.NewSerializer(prefix, useStrict, sourceOverride)
 }