feat(serializers.prometheus): Provide option to reduce payload size by removing HELP from payload (#11690)

config/config.go

@@ -342,10 +342,9 @@ func (c *Config) LoadDirectory(path string) error {
 }
 
 // Try to find a default config file at these locations (in order):
-//   1. $TELEGRAF_CONFIG_PATH
-//   2. $HOME/.telegraf/telegraf.conf
-//   3. /etc/telegraf/telegraf.conf
-//
+//  1. $TELEGRAF_CONFIG_PATH
+//  2. $HOME/.telegraf/telegraf.conf
+//  3. /etc/telegraf/telegraf.conf
 func getDefaultConfigPath() (string, error) {
 	envfile := os.Getenv("TELEGRAF_CONFIG_PATH")
 	homefile := os.ExpandEnv("${HOME}/.telegraf/telegraf.conf")
@@ -1165,6 +1164,7 @@ func (c *Config) buildSerializer(tbl *ast.Table) (serializers.Serializer, error)
 	c.getFieldBool(tbl, "prometheus_export_timestamp", &sc.PrometheusExportTimestamp)
 	c.getFieldBool(tbl, "prometheus_sort_metrics", &sc.PrometheusSortMetrics)
 	c.getFieldBool(tbl, "prometheus_string_as_label", &sc.PrometheusStringAsLabel)
+	c.getFieldBool(tbl, "prometheus_compact_encoding", &sc.PrometheusCompactEncoding)
 
 	if c.hasErrs() {
 		return nil, c.firstErr()
@@ -1233,6 +1233,7 @@ func (c *Config) missingTomlField(_ reflect.Type, key string) error {
 		"influx_max_line_bytes", "influx_sort_fields", "influx_uint_support",
 		"json_timestamp_format", "json_timestamp_units",
 		"prometheus_export_timestamp", "prometheus_sort_metrics", "prometheus_string_as_label",
+		"prometheus_compact_encoding",
 		"splunkmetric_hec_routing", "splunkmetric_multimetric",
 		"wavefront_disable_prefix_conversion", "wavefront_source_override", "wavefront_use_strict":
 	default:

plugins/serializers/prometheus/README.md

@@ -31,6 +31,10 @@ reporting others every bucket/quantile will continue to exist.
   ## discarded.
   prometheus_string_as_label = false
 
+  ## Encode metrics without HELP metadata. This helps reduce the payload
+  ## size.
+  prometheus_compact_encoding = false
+
   ## Data format to output.
   ## Each data format has its own unique set of configuration options, read
   ## more about them here:

plugins/serializers/prometheus/collection.go

@@ -412,10 +412,13 @@ func (c *Collection) GetProto() []*dto.MetricFamily {
 	for _, entry := range c.GetEntries(c.config.MetricSortOrder) {
 		mf := &dto.MetricFamily{
 			Name: proto.String(entry.Family.Name),
-			Help: proto.String(helpString),
 			Type: MetricType(entry.Family.Type),
 		}
 
+		if !c.config.CompactEncoding {
+			mf.Help = proto.String(helpString)
+		}
+
 		for _, metric := range c.GetMetrics(entry, c.config.MetricSortOrder) {
 			l := make([]*dto.LabelPair, 0, len(metric.Labels))
 			for _, label := range metric.Labels {

plugins/serializers/prometheus/prometheus.go

@@ -36,6 +36,10 @@ type FormatConfig struct {
 	TimestampExport TimestampExport
 	MetricSortOrder MetricSortOrder
 	StringHandling  StringHandling
+	// CompactEncoding defines whether to include
+	// HELP metadata in Prometheus payload. Setting to true
+	// helps to reduce payload size.
+	CompactEncoding bool
 }
 
 type Serializer struct {

plugins/serializers/prometheus/prometheus_test.go

@@ -156,6 +156,26 @@ http_request_duration_seconds_count 0
 # HELP cpu_time_idle Telegraf collected metric
 # TYPE cpu_time_idle untyped
 cpu_time_idle{host="example.org"} 42 1574279268000
+`),
+		},
+		{
+			name: "simple with CompactEncoding",
+			config: FormatConfig{
+				CompactEncoding: true,
+			},
+			metric: testutil.MustMetric(
+				"cpu",
+				map[string]string{
+					"host": "example.org",
+				},
+				map[string]interface{}{
+					"time_idle": 42.0,
+				},
+				time.Unix(1574279268, 0),
+			),
+			expected: []byte(`
+# TYPE cpu_time_idle untyped
+cpu_time_idle{host="example.org"} 42
 `),
 		},
 	}
@@ -165,6 +185,7 @@ cpu_time_idle{host="example.org"} 42 1574279268000
 				MetricSortOrder: SortMetrics,
 				TimestampExport: tt.config.TimestampExport,
 				StringHandling:  tt.config.StringHandling,
+				CompactEncoding: tt.config.CompactEncoding,
 			})
 			require.NoError(t, err)
 			actual, err := s.Serialize(tt.metric)

plugins/serializers/registry.go

@@ -130,6 +130,9 @@ type Config struct {
 	// Output string fields as metric labels; when false string fields are
 	// discarded.
 	PrometheusStringAsLabel bool `toml:"prometheus_string_as_label"`
+
+	// Encode metrics without HELP metadata. This helps reduce the payload size.
+	PrometheusCompactEncoding bool `toml:"prometheus_compact_encoding"`
 }
 
 // NewSerializer a Serializer interface based on the given config.
@@ -206,6 +209,7 @@ func NewPrometheusSerializer(config *Config) (Serializer, error) {
 		TimestampExport: exportTimestamp,
 		MetricSortOrder: sortMetrics,
 		StringHandling:  stringAsLabels,
+		CompactEncoding: config.PrometheusCompactEncoding,
 	})
 }