From f85dbe7be181beb5c7579b9e74b8cef62bf5bea4 Mon Sep 17 00:00:00 2001
From: Ariel Valentin <arielvalentin@github.com>
Date: Sat, 28 Oct 2023 12:50:09 -0500
Subject: [PATCH] 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.
---
 instrumentation/rack/example/trace_demonstration.rb             | 2 +-
 instrumentation/rack/example/trace_demonstration2.rb            | 2 +-
 instrumentation/rack/example/trace_demonstration3.rb            | 2 +-
 .../lib/opentelemetry/instrumentation/rack/instrumentation.rb   | 2 +-
 .../opentelemetry/instrumentation/rack/instrumentation_test.rb  | 2 +-
 5 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/instrumentation/rack/example/trace_demonstration.rb b/instrumentation/rack/example/trace_demonstration.rb
index e6253f57cf..02fc8a7128 100644
--- a/instrumentation/rack/example/trace_demonstration.rb
+++ b/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
diff --git a/instrumentation/rack/example/trace_demonstration2.rb b/instrumentation/rack/example/trace_demonstration2.rb
index c6ac649e9e..66941cfb07 100644
--- a/instrumentation/rack/example/trace_demonstration2.rb
+++ b/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('/')
diff --git a/instrumentation/rack/example/trace_demonstration3.rb b/instrumentation/rack/example/trace_demonstration3.rb
index a444ecfebe..38226a72a1 100644
--- a/instrumentation/rack/example/trace_demonstration3.rb
+++ b/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
diff --git a/instrumentation/rack/lib/opentelemetry/instrumentation/rack/instrumentation.rb b/instrumentation/rack/lib/opentelemetry/instrumentation/rack/instrumentation.rb
index 35be3a5199..4ae265b7e0 100644
--- a/instrumentation/rack/lib/opentelemetry/instrumentation/rack/instrumentation.rb
+++ b/instrumentation/rack/lib/opentelemetry/instrumentation/rack/instrumentation.rb
@@ -29,7 +29,7 @@ class Instrumentation < OpenTelemetry::Instrumentation::Base
         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
+        option :use_rack_events,          default: true, validate: :boolean
 
         # Temporary Helper for Sinatra and ActionPack middleware to use during installation
         #
diff --git a/instrumentation/rack/test/opentelemetry/instrumentation/rack/instrumentation_test.rb b/instrumentation/rack/test/opentelemetry/instrumentation/rack/instrumentation_test.rb
index 2814bde0df..1db654ddd3 100644
--- a/instrumentation/rack/test/opentelemetry/instrumentation/rack/instrumentation_test.rb
+++ b/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