feat: Rails Rack Events

This PR makes it possible for users to toggle between using the Rack Events and Middleware based instrumentation

See open-telemetry#341
Depends on open-telemetry#342

instrumentation/action_pack/Gemfile

@@ -10,5 +10,6 @@ gemspec
 
 group :test do
   gem 'opentelemetry-instrumentation-base', path: '../../instrumentation/base'
+  gem 'opentelemetry-instrumentation-rack', path: '../../instrumentation/rack'
   gem 'pry-byebug'
 end

instrumentation/action_pack/lib/opentelemetry/instrumentation/action_pack/railtie.rb

@@ -14,7 +14,7 @@ class Railtie < ::Rails::Railtie
 
           app.middleware.insert_before(
             0,
-            OpenTelemetry::Instrumentation::Rack::Middlewares::TracerMiddleware
+            *OpenTelemetry::Instrumentation::Rack::Instrumentation.instance.middleware_args
           )
         end
       end

instrumentation/action_pack/test/test_helpers/app_config.rb

@@ -21,8 +21,10 @@ def initialize_app(use_exceptions_app: false, remove_rack_tracer_middleware: fal
     new_app.config.eager_load = false
 
     # Prevent tests from creating log/*.log
+    use_stderr = ENV.fetch('RAILS_LOG_STDERR', 'false') == 'true'
+    io_stream = use_stderr ? $stderr : File::NULL
     level = ENV.fetch('OTEL_LOG_LEVEL', 'fatal').to_sym
-    new_app.config.logger = Logger.new($stderr, level: level)
+    new_app.config.logger = Logger.new(io_stream, level: level)
     new_app.config.log_level = level
 
     new_app.config.filter_parameters = [:param_to_be_filtered]
@@ -53,6 +55,9 @@ def remove_rack_middleware(application)
     application.middleware.delete(
       OpenTelemetry::Instrumentation::Rack::Middlewares::TracerMiddleware
     )
+    application.middleware.delete(
+      Rack::Events
+    )
   end
 
   def add_exceptions_app(application)