feat(rack)! Use Rack Events By Default (#709)

* feat(rack)! Use Rack Events By Default

I have been running the `Rack::Events` based instrumentation in our production workloads since 2023-10-23.

There is no noticeable difference in performance, however applications using `Rack::BodyProxy`
to stream responses will notice a slight increase in latency since it will include timings
writing response output to the socket.

* squash: fix invalid HTTP responses in tests

* squash: Remove redundant test

* squash: Update rack error description

* Update instrumentation.rb

Co-authored-by: Kayla Reopelle (she/her) <87386821+kaylareopelle@users.noreply.github.com>

---------

Co-authored-by: Kayla Reopelle (she/her) <87386821+kaylareopelle@users.noreply.github.com>

instrumentation/action_pack/test/test_helpers/app_config.rb

@@ -48,9 +48,7 @@ def initialize_app(use_exceptions_app: false, remove_rack_tracer_middleware: fal
   private
 
   def remove_rack_middleware(application)
-    application.middleware.delete(
-      OpenTelemetry::Instrumentation::Rack::Middlewares::TracerMiddleware
-    )
+    application.middleware.delete(Rack::Events)
   end
 
   def add_exceptions_app(application)

instrumentation/action_pack/test/test_helpers/middlewares/redirect_middleware.rb

@@ -10,7 +10,7 @@ def initialize(app, _options = {})
   end
 
   def call(env)
-    return [307, {}, 'Temporary Redirect'] if should_redirect?(env)
+    return [307, { 'Location' => '/ok', 'Content-Type' => 'text/plain' }, ['Temporary Redirect']] if should_redirect?(env)
 
     @app.call(env)
   end

instrumentation/grape/test/opentelemetry/instrumentation/grape_test.rb

@@ -272,7 +272,7 @@ class RaisedErrorAPI < Grape::API
       it 'sets span status to error' do
         _(span.name).must_equal expected_span_name
         _(span.status.code).must_equal OpenTelemetry::Trace::Status::ERROR
-        _(span.status.description).must_equal "Unhandled exception of type: #{expected_error_type}"
+        _(span.status.description).must_equal expected_error_type
       end
 
       it 'records the exception event' do
@@ -316,7 +316,7 @@ class ErrorInFilterAPI < Grape::API
       it 'sets span status to error' do
         _(span.name).must_equal expected_span_name
         _(span.status.code).must_equal OpenTelemetry::Trace::Status::ERROR
-        _(span.status.description).must_equal "Unhandled exception of type: #{expected_error_type}"
+        _(span.status.description).must_equal expected_error_type
       end
 
       it 'records the exception event' do

instrumentation/rack/example/trace_demonstration.rb

@@ -18,7 +18,7 @@
 builder = Rack::Builder.app do
   # integration should be automatic in web frameworks (like rails),
   # but for a plain Rack application, enable it in your config.ru, e.g.,
-  use OpenTelemetry::Instrumentation::Rack::Middlewares::TracerMiddleware
+  use ::Rack::Events, [OpenTelemetry::Instrumentation::Rack::Middlewares::EventHandler.new]
 
   app = ->(_env) { [200, { 'Content-Type' => 'text/plain' }, ['All responses are OK']] }
   run app

instrumentation/rack/example/trace_demonstration2.rb

@@ -24,7 +24,7 @@
 end
 
 # integrate instrumentation explicitly:
-builder.use OpenTelemetry::Instrumentation::Rack::Middlewares::TracerMiddleware
+builder.use ::Rack::Events, [OpenTelemetry::Instrumentation::Rack::Middlewares::EventHandler.new]
 
 # demonstrate tracing (span output to console):
 puts Rack::MockRequest.new(builder).get('/')

instrumentation/rack/example/trace_demonstration3.rb

@@ -19,7 +19,7 @@
 builder = Rack::Builder.app do
   # integration should be automatic in web frameworks (like rails),
   # but for a plain Rack application, enable it in your config.ru, e.g.,
-  use OpenTelemetry::Instrumentation::Rack::Middlewares::TracerMiddleware
+  use ::Rack::Events, [OpenTelemetry::Instrumentation::Rack::Middlewares::EventHandler.new]
 
   app = ->(_env) { [200, { 'Content-Type' => 'text/plain' }, ['All responses are OK']] }
   run app

instrumentation/rack/lib/opentelemetry/instrumentation/rack/instrumentation.rb

@@ -28,8 +28,8 @@ class Instrumentation < OpenTelemetry::Instrumentation::Base
         option :url_quantization,         default: nil,   validate: :callable
         option :untraced_requests,        default: nil,   validate: :callable
         option :response_propagators,     default: [],    validate: :array
-        # This option is only valid for applicaitons using Rack 2.0 or greater
-        option :use_rack_events,          default: false, validate: :boolean
+        # This option is only valid for applications using Rack 2.0 or greater
+        option :use_rack_events,          default: true, validate: :boolean
 
         # Temporary Helper for Sinatra and ActionPack middleware to use during installation
         #

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

@@ -90,7 +90,7 @@ def on_error(request, _, error)
             return unless span.recording?
 
             span.record_exception(error)
-            span.status = OpenTelemetry::Trace::Status.error
+            span.status = OpenTelemetry::Trace::Status.error(error.class.name)
           rescue StandardError => e
             OpenTelemetry.handle_error(exception: e)
           end

instrumentation/rack/test/opentelemetry/instrumentation/rack/instrumentation_test.rb

@@ -32,7 +32,7 @@
       _(instrumentation.config[:url_quantization]).must_be_nil
       _(instrumentation.config[:untraced_requests]).must_be_nil
       _(instrumentation.config[:response_propagators]).must_be_empty
-      _(instrumentation.config[:use_rack_events]).must_equal false
+      _(instrumentation.config[:use_rack_events]).must_equal true
     end
   end