telemetry: submit orchestrion_usage counter metric

To make it easier to get data about orchestrion usage, start submitting
a counter metric in telemetry for applications built with orchestrion.

ddtrace/tracer/telemetry.go

@@ -7,7 +7,9 @@ package tracer
 
 import (
 	"fmt"
+	"slices"
 	"strings"
+	"testing"
 
 	"gopkg.in/DataDog/dd-trace-go.v1/internal/telemetry"
 )
@@ -108,9 +110,21 @@ func startTelemetry(c *config) {
 				Value: fmt.Sprintf("rate:%f_maxPerSecond:%f", rule.Rate, rule.MaxPerSecond)})
 	}
 	if c.orchestrionCfg.Enabled {
+		tags := make([]string, 0, len(c.orchestrionCfg.Metadata))
 		for k, v := range c.orchestrionCfg.Metadata {
 			telemetryConfigs = append(telemetryConfigs, telemetry.Configuration{Name: "orchestrion_" + k, Value: v})
+			tags = append(tags, k+":"+v)
 		}
+		if testing.Testing() {
+			// In tests, ensure tags are consistently ordered...
+			slices.Sort(tags)
+		}
+		telemetry.GlobalClient.Count(
+			telemetry.NamespaceTracers,
+			"orchestrion_usage", 1,
+			tags,
+			false, // Go-specific
+		)
 	}
 	telemetryConfigs = append(telemetryConfigs, additionalConfigs...)
 	telemetry.GlobalClient.ProductChange(telemetry.NamespaceTracers, true, telemetryConfigs)

ddtrace/tracer/telemetry_test.go

@@ -154,11 +154,19 @@ func TestTelemetryEnabled(t *testing.T) {
 		telemetryClient := new(telemetrytest.MockClient)
 		defer telemetry.MockGlobalClient(telemetryClient)()
 
+		telemetryClient.On("Count",
+			telemetry.NamespaceTracers,
+			"orchestrion_usage", 1.0,
+			[]string{"k1:v1", "k2:v2"},
+			false,
+		).Return()
+
 		Start(WithOrchestrion(map[string]string{"k1": "v1", "k2": "v2"}))
 		defer Stop()
 
 		telemetry.Check(t, telemetryClient.Configuration, "orchestrion_enabled", true)
 		telemetry.Check(t, telemetryClient.Configuration, "orchestrion_k1", "v1")
 		telemetry.Check(t, telemetryClient.Configuration, "orchestrion_k2", "v2")
+		telemetryClient.AssertExpectations(t)
 	})
 }

internal/telemetry/telemetrytest/telemetrytest.go

@@ -82,7 +82,6 @@ func (c *MockClient) Record(ns telemetry.Namespace, _ telemetry.MetricKind, name
 
 // Count counts the value for the given metric
 func (c *MockClient) Count(ns telemetry.Namespace, name string, val float64, tags []string, common bool) {
-	c.On("Count", ns, name, val, tags, common).Return()
 	_ = c.Called(ns, name, val, tags, common)
 }