[cmd/telemetrygen] Allow configuring Sum and Gauge metrics via CLI (o…

…pen-telemetry#26667)

**Description:** <Describe what has changed.>
Adding a feature - Allow configuring Sum and Gauge metrics in
`telemetrygen` via CLI

---------

Co-authored-by: Pablo Baeyens <pbaeyens31+github@gmail.com>

.chloggen/telemetrygen-add-metric-types.yaml

@@ -0,0 +1,25 @@
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: 'enhancement'
+
+# The name of the component, or a single word describing the area of concern, (e.g. filelogreceiver)
+component: cmd/telemetrygen
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Add CLI option for selecting different metric types
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [26667]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext:
+
+# If your change doesn't affect end users or the exported elements of any package,
+# you should instead start your pull request title with [chore] or use the "Skip Changelog" label.
+# Optional: The change log or logs in which this entry should be included.
+# e.g. '[user]' or '[user, api]'
+# Include 'user' if the change is relevant to end users.
+# Include 'api' if there is a change to a library API.
+# Default: '[user]'
+change_logs: [user]

cmd/telemetrygen/internal/metrics/config.go

@@ -13,10 +13,15 @@ import (
 type Config struct {
 	common.Config
 	NumMetrics int
+	MetricType metricType
 }
 
 // Flags registers config flags.
 func (c *Config) Flags(fs *pflag.FlagSet) {
+	// Use Gauge as default metric type.
+	c.MetricType = metricTypeGauge
+
 	c.CommonFlags(fs)
+	fs.Var(&c.MetricType, "metric-type", "Metric type enum. must be one of 'Gauge' or 'Sum'")
 	fs.IntVar(&c.NumMetrics, "metrics", 1, "Number of metrics to generate in each worker (ignored if duration is provided)")
 }

cmd/telemetrygen/internal/metrics/metrics.go

@@ -28,6 +28,7 @@ func Start(cfg *Config) error {
 	if err != nil {
 		return err
 	}
+	logger.Info("starting the metrics generator with configuration", zap.Any("config", cfg))
 
 	grpcExpOpt := []otlpmetricgrpc.Option{
 		otlpmetricgrpc.WithEndpoint(cfg.Endpoint),
@@ -104,6 +105,7 @@ func Run(c *Config, exp sdkmetric.Exporter, logger *zap.Logger) error {
 		wg.Add(1)
 		w := worker{
 			numMetrics:     c.NumMetrics,
+			metricType:     c.MetricType,
 			limitPerSecond: limit,
 			totalDuration:  c.TotalDuration,
 			running:        running,

cmd/telemetrygen/internal/metrics/metrics_types.go

@@ -0,0 +1,36 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package metrics
+
+import (
+	"errors"
+)
+
+type metricType string
+
+const (
+	metricTypeGauge = "Gauge"
+	metricTypeSum   = "Sum"
+)
+
+// String is used both by fmt.Print and by Cobra in help text
+func (e *metricType) String() string {
+	return string(*e)
+}
+
+// Set must have pointer receiver so it doesn't change the value of a copy
+func (e *metricType) Set(v string) error {
+	switch v {
+	case "Gauge", "Sum":
+		*e = metricType(v)
+		return nil
+	default:
+		return errors.New(`must be one of "Gauge" or "Sum"`)
+	}
+}
+
+// Type is only used in help text
+func (e *metricType) Type() string {
+	return "metricType"
+}

cmd/telemetrygen/internal/metrics/worker.go

@@ -18,6 +18,7 @@ import (
 
 type worker struct {
 	running        *atomic.Bool    // pointer to shared flag that indicates it's time to stop the test
+	metricType     metricType      // type of metric to generate
 	numMetrics     int             // how many metrics the worker has to generate (only when duration==0)
 	totalDuration  time.Duration   // how long to run the test for (overrides `numMetrics`)
 	limitPerSecond rate.Limit      // how many metrics per second to generate
@@ -28,29 +29,48 @@ type worker struct {
 
 func (w worker) simulateMetrics(res *resource.Resource, exporter sdkmetric.Exporter) {
 	limiter := rate.NewLimiter(w.limitPerSecond, 1)
-	var i int64
 
+	var i int64
 	for w.running.Load() {
-		rm := metricdata.ResourceMetrics{
-			Resource: res,
-			ScopeMetrics: []metricdata.ScopeMetrics{
-				{
-					Metrics: []metricdata.Metrics{
+		var metrics []metricdata.Metrics
+
+		switch w.metricType {
+		case metricTypeGauge:
+			metrics = append(metrics, metricdata.Metrics{
+				Name: "gen",
+				Data: metricdata.Gauge[int64]{
+					DataPoints: []metricdata.DataPoint[int64]{
+						{
+							Time:  time.Now(),
+							Value: i,
+						},
+					},
+				},
+			})
+		case metricTypeSum:
+			metrics = append(metrics, metricdata.Metrics{
+				Name: "gen",
+				Data: metricdata.Sum[int64]{
+					IsMonotonic: true,
+					Temporality: metricdata.CumulativeTemporality,
+					DataPoints: []metricdata.DataPoint[int64]{
 						{
-							Name: "gen",
-							Data: metricdata.Gauge[int64]{
-								DataPoints: []metricdata.DataPoint[int64]{
-									{
-										Time:  time.Now(),
-										Value: i,
-									},
-								},
-							},
+							StartTime: time.Now().Add(-1 * time.Second),
+							Time:      time.Now(),
+							Value:     i,
 						},
 					},
 				},
-			},
+			})
+		default:
+			w.logger.Fatal("unknown metric type")
+		}
+
+		rm := metricdata.ResourceMetrics{
+			Resource:     res,
+			ScopeMetrics: []metricdata.ScopeMetrics{{Metrics: metrics}},
 		}
+
 		if err := exporter.Export(context.Background(), &rm); err != nil {
 			w.logger.Fatal("exporter failed", zap.Error(err))
 		}

cmd/telemetrygen/internal/metrics/worker_test.go

@@ -48,6 +48,7 @@ func TestFixedNumberOfMetrics(t *testing.T) {
 			WorkerCount: 1,
 		},
 		NumMetrics: 5,
+		MetricType: metricTypeSum,
 	}
 
 	exp := &mockExporter{}
@@ -69,6 +70,7 @@ func TestRateOfMetrics(t *testing.T) {
 			TotalDuration: time.Second / 2,
 			WorkerCount:   1,
 		},
+		MetricType: metricTypeSum,
 	}
 	exp := &mockExporter{}
 
@@ -88,6 +90,7 @@ func TestUnthrottled(t *testing.T) {
 			TotalDuration: 1 * time.Second,
 			WorkerCount:   1,
 		},
+		MetricType: metricTypeSum,
 	}
 	exp := &mockExporter{}