fix: handle broken instrumentation case

instrumentation/rack/lib/opentelemetry/instrumentation/rack/middlewares/event_handler.rb

@@ -42,7 +42,7 @@ module Middlewares
         class EventHandler
           include ::Rack::Events::Abstract
 
-          TOKEN_KEY = 'otel.context.token'
+          RACK_OTEL_CONTEXT_KEY = 'otel.rack.context.token'
           GOOD_HTTP_STATUSES = (100..499)
 
           # Creates a server span for this current request using the incoming parent context
@@ -58,7 +58,7 @@ def on_start(request, _)
             span = create_span(parent_context, request)
             span_ctx = OpenTelemetry::Trace.context_with_span(span, parent_context: parent_context)
             rack_ctx = OpenTelemetry::Instrumentation::Rack.context_with_span(span, parent_context: span_ctx)
-            request.env[TOKEN_KEY] = OpenTelemetry::Context.attach(rack_ctx)
+            request.env[RACK_OTEL_CONTEXT_KEY] = [OpenTelemetry::Context.attach(rack_ctx), rack_ctx]
           rescue StandardError => e
             OpenTelemetry.handle_error(exception: e)
           end
@@ -194,10 +194,11 @@ def request_span_attributes(env)
           end
 
           def detach_context(request)
-            return nil unless request.env[TOKEN_KEY]
+            return nil unless request.env[RACK_OTEL_CONTEXT_KEY]
 
-            OpenTelemetry::Trace.current_span.finish
-            OpenTelemetry::Context.detach(request.env[TOKEN_KEY])
+            token, rack_ctx = request.env[RACK_OTEL_CONTEXT_KEY]
+            OpenTelemetry::Trace.current_span(rack_ctx).finish
+            OpenTelemetry::Context.detach(token)
           rescue StandardError => e
             OpenTelemetry.handle_error(exception: e)
           end

instrumentation/rack/test/opentelemetry/instrumentation/rack/middlewares/event_handler_test.rb

@@ -67,6 +67,27 @@
     instrumentation.install(config)
   end
 
+  # Simulating buggy instrumentation that starts a span, sets the ctx
+  # but fails to detach or close the span
+  describe 'broken instrumentation' do
+    let(:service) do
+      lambda do |_env|
+        span = OpenTelemetry.tracer_provider.tracer('buggy').start_span('I never close')
+        OpenTelemetry::Context.attach(OpenTelemetry::Trace.context_with_span(span))
+        [200, { 'Content-Type' => 'text/plain' }, response_body]
+      end
+    end
+
+    it 'still closes the rack span' do
+      assert_raises OpenTelemetry::Context::DetachError do
+        get uri, {}, headers
+      end
+      _(finished_spans.size).must_equal 1
+      _(rack_span.name).must_equal 'HTTP GET'
+      OpenTelemetry::Context.clear
+    end
+  end
+
   describe '#call' do
     before do
       get uri, {}, headers