Add telemetry for opentracing

lib/datadog/core/telemetry/collector.rb

@@ -146,6 +146,7 @@ def additional_payload_variables
           options['logger.instance'] = configuration.logger.instance.class.to_s
           options['appsec.enabled'] = configuration.dig('appsec', 'enabled') if configuration.respond_to?('appsec')
           options['tracing.opentelemetry.enabled'] = !defined?(Datadog::OpenTelemetry::LOADED).nil?
+          options['tracing.opentracing.enabled'] = !defined?(Datadog::OpenTracer::LOADED).nil?
           options.compact!
           options
         end

lib/datadog/opentracer.rb

@@ -22,3 +22,12 @@
 
 # Modify the OpenTracing module functions
 ::OpenTracing.singleton_class.prepend(Datadog::OpenTracer::GlobalTracer)
+
+module Datadog
+  # Datadog OpenTracing integration.
+  # DEV: This module should be named `Datadog::OpenTracing` to match the gem (`opentracing`).
+  module OpenTracer
+    # Used by Telemetry to decide if OpenTracing instrumentation is enabled
+    LOADED = true
+  end
+end

spec/datadog/core/telemetry/collector_spec.rb

@@ -293,6 +293,14 @@
 
       it { is_expected.to include('tracing.opentelemetry.enabled' => true) }
     end
+
+    context 'when OpenTracing is enabled' do
+      before do
+        stub_const('Datadog::OpenTracer::LOADED', true)
+      end
+
+      it { is_expected.to include('tracing.opentracing.enabled' => true) }
+    end
   end
 
   describe '#dependencies' do