add railtie based RUM Rack instrumentation

examples/rails-7-barebones/Gemfile

@@ -10,7 +10,7 @@ gem "puma"
 gem "rails", "~> 7.0.3"
 
 # instrumentation
-gem "opentelemetry-instrumentation-rails", "~> 0.21.0"
+gem "opentelemetry-instrumentation-rails", "~> 0.22.0"
 gem "splunk-otel", path: ENV.fetch("SPLUNK_OTEL_LOCATION", "../../")
 
 # tests

lib/splunk/otel.rb

@@ -167,3 +167,4 @@ def service_name_warning
 
 require "splunk/otel/logging"
 require "splunk/otel/common"
+require "splunk/otel/instrumentation/action_pack"

lib/splunk/otel/common.rb

@@ -9,6 +9,10 @@ module Common
       CORS_EXPOSE_HEADER = "Access-Control-Expose-Headers"
       SERVER_TIMING_HEADER = "Server-Timing"
 
+      # rubocop:disable Lint/MissingCopEnableDirective
+      # rubocop:disable Metrics/PerceivedComplexity
+      # rubocop:disable Metrics/MethodLength
+      # rubocop:disable Metrics/AbcSize
       def rum_headers(headers)
         span = OpenTelemetry::Trace.current_span
 
@@ -20,7 +24,12 @@ def rum_headers(headers)
         flags = span.context.trace_flags.sampled? ? "01" : "00"
 
         trace_parent = [version, trace_id, span_id, flags]
-        headers[SERVER_TIMING_HEADER] = "traceparent;desc=\"#{trace_parent.join("-")}\""
+        headers[SERVER_TIMING_HEADER] = if (headers[SERVER_TIMING_HEADER] || "").empty?
+                                          "traceparent;desc=\"#{trace_parent.join("-")}\""
+                                        else
+                                          # rubocop:disable Layout/LineLength
+                                          "#{headers[SERVER_TIMING_HEADER]}, traceparent;desc=\"#{trace_parent.join("-")}\""
+                                        end
 
         # TODO: check if this needs to be conditioned on CORS
         headers[CORS_EXPOSE_HEADER] = if (headers[CORS_EXPOSE_HEADER] || "").empty?

lib/splunk/otel/instrumentation/action_pack.rb

@@ -0,0 +1,14 @@
+# frozen_string_literal: true
+
+module Splunk
+  module Otel
+    module Instrumentation
+      # Contains the RUM instrumentation for the ActionPack gem
+      module ActionPack
+      end
+    end
+  end
+end
+
+require_relative "./action_pack/instrumentation"
+require_relative "./action_pack/version"

lib/splunk/otel/instrumentation/action_pack/instrumentation.rb

@@ -0,0 +1,41 @@
+# frozen_string_literal: true
+
+require "opentelemetry"
+require "opentelemetry-instrumentation-base"
+
+module Splunk
+  module Otel
+    module Instrumentation
+      module ActionPack
+        # The Instrumentation class contains logic to detect and install the ActionPack instrumentation
+        class Instrumentation < OpenTelemetry::Instrumentation::Base
+          MINIMUM_VERSION = Gem::Version.new("5.2.0")
+
+          install do |_config|
+            require_railtie
+          end
+
+          present do
+            defined?(::ActionController)
+          end
+
+          compatible do
+            gem_version >= MINIMUM_VERSION
+          end
+
+          option :enable_recognize_route, default: false, validate: :boolean
+
+          private
+
+          def gem_version
+            ::ActionPack.version
+          end
+
+          def require_railtie
+            require_relative "railtie"
+          end
+        end
+      end
+    end
+  end
+end

lib/splunk/otel/instrumentation/action_pack/railtie.rb

@@ -0,0 +1,28 @@
+# frozen_string_literal: true
+
+require "rack/etag"
+require_relative "../rack"
+
+module Splunk
+  module Otel
+    module Instrumentation
+      module ActionPack
+        # Install the Rack middleware for RUM responses
+        class Railtie < ::Rails::Railtie
+          config.before_initialize do |app|
+            case Rails.version
+            when /^7\./
+              # TODO: can be removed once https://github.com/rails/rails/issues/45607 is merged
+              app.middleware.insert_before(
+                ::Rack::ETag,
+                Splunk::Otel::Rack::RumMiddleware
+              )
+            else
+              app.middleware.use Splunk::Otel::Rack::RumMiddleware
+            end
+          end
+        end
+      end
+    end
+  end
+end

lib/splunk/otel/instrumentation/action_pack/version.rb

@@ -0,0 +1,11 @@
+# frozen_string_literal: true
+
+module Splunk
+  module Otel
+    module Instrumentation
+      module ActionPack
+        VERSION = "0.1.0"
+      end
+    end
+  end
+end

splunk-otel.gemspec

@@ -28,21 +28,22 @@ Gem::Specification.new do |spec|
   spec.add_dependency "opentelemetry-api", "~> 1.0"
   spec.add_dependency "opentelemetry-exporter-jaeger", "~> 0.20.1"
   spec.add_dependency "opentelemetry-exporter-otlp", "~> 0.21.0"
+  spec.add_dependency "opentelemetry-instrumentation-base", "~> 0.21.0"
   spec.add_dependency "opentelemetry-propagator-b3", "~> 0.19.2"
   spec.add_dependency "opentelemetry-sdk", "~> 1.0"
 
   # development dependencies
-  spec.add_development_dependency "rack-test", "~> 1.1"
+  spec.add_development_dependency "rails"
   spec.add_development_dependency "rake", "~> 13.0"
   spec.add_development_dependency "rubocop", "~> 1.25"
   spec.add_development_dependency "rubocop-rake", "~> 0.6.0"
   spec.add_development_dependency "simplecov", "~> 0.21.2"
-  spec.add_development_dependency  "test-unit", "~> 3.0"
+  spec.add_development_dependency "test-unit", "~> 3.0"
 
-  # for testing the rack middleware
-  spec.add_development_dependency  "opentelemetry-instrumentation-action_pack", "~> 0.1.4"
-  spec.add_development_dependency  "opentelemetry-instrumentation-rack", "~> 0.20"
-  spec.add_development_dependency  "rack", "~> 2.2"
+  spec.add_development_dependency "opentelemetry-instrumentation-action_pack", "~> 0.2.0"
+  spec.add_development_dependency "opentelemetry-instrumentation-rack", "~> 0.21"
+  spec.add_development_dependency "rack", "~> 2.2"
+  spec.add_development_dependency "rack-test", "~> 1.1"
 
   spec.metadata = {
     "rubygems_mfa_required" => "true"

test/splunk/instrumentation/rack_test.rb

@@ -11,11 +11,7 @@ module Splunk
   class RumRackTest < Test::Unit::TestCase
     include Rack::Test::Methods
 
-    EXPORTER = OpenTelemetry::SDK::Trace::Export::InMemorySpanExporter.new
-
     def setup
-      EXPORTER.reset
-
       with_env("OTEL_SERVICE_NAME" => "test-service") do
         span_processor = OpenTelemetry::SDK::Trace::Export::SimpleSpanProcessor.new(EXPORTER)
         Splunk::Otel.configure do |c|
@@ -26,7 +22,7 @@ def setup
     end
 
     def teardown
-      OpenTelemetry.tracer_provider.shutdown
+      reset_opentelemetry
     end
 
     def app

test/splunk/instrumentation/rails_test.rb

@@ -0,0 +1,62 @@
+# frozen_string_literal: true
+
+require "rails"
+
+require "test_helper"
+require "opentelemetry/sdk"
+require "opentelemetry/instrumentation/rack"
+require "opentelemetry/instrumentation/action_pack"
+require "splunk/otel"
+require "splunk/otel/instrumentation/rack"
+require "splunk/otel/instrumentation/action_pack"
+require "splunk/otel/instrumentation/action_pack/railtie"
+require "rack/test"
+require "test_helpers/app_config"
+
+module Splunk
+  class RumRailsTest < Test::Unit::TestCase
+    include Rack::Test::Methods
+
+    def setup
+      with_env("OTEL_SERVICE_NAME" => "test-service") do
+        span_processor = OpenTelemetry::SDK::Trace::Export::SimpleSpanProcessor.new(EXPORTER)
+        Splunk::Otel.configure do |c|
+          c.add_span_processor span_processor
+          c.use "OpenTelemetry::Instrumentation::ActionPack"
+          c.use "Splunk::Otel::Instrumentation::ActionPack"
+        end
+      end
+    end
+
+    def teardown
+      reset_opentelemetry
+    end
+
+    def app
+      default_rails_app = AppConfig.initialize_app
+      ::Rails.application = default_rails_app
+
+      default_rails_app
+    end
+
+    test "RUM response from Rack middleware" do
+      get "/ok"
+
+      assert last_response.ok?
+      assert_equal "OK", last_response.body
+
+      response_headers = last_response.headers
+      assert_equal "Server-Timing", response_headers["Access-Control-Expose-Headers"]
+
+      # the only started span is the one done by the Rack middleware
+      # so the 1 span in the exporter is the one returned in the response
+      assert_equal(1, EXPORTER.finished_spans.size)
+      span = EXPORTER.finished_spans.first
+      expected_trace_id = span.trace_id.unpack1("H*")
+      expected_span_id = span.span_id.unpack1("H*")
+
+      assert_match("traceparent;desc=\"00-#{expected_trace_id}-#{expected_span_id}-01\"",
+                   response_headers["Server-Timing"])
+    end
+  end
+end

test/test_helper.rb

@@ -8,6 +8,8 @@
 
 require "test-unit"
 
+EXPORTER = OpenTelemetry::SDK::Trace::Export::InMemorySpanExporter.new
+
 def with_env(new_env)
   env_to_reset = ENV.select { |k, _| new_env.key?(k) }
   keys_to_delete = new_env.keys - ENV.keys
@@ -17,3 +19,17 @@ def with_env(new_env)
   env_to_reset.each_pair { |k, v| ENV[k] = v }
   keys_to_delete.each { |k| ENV.delete(k) }
 end
+
+def reset_opentelemetry
+  EXPORTER.reset
+
+  OpenTelemetry.instance_variable_set(
+    :@tracer_provider,
+    OpenTelemetry::Internal::ProxyTracerProvider.new
+  )
+
+  # OpenTelemetry will load the defaults
+  # on the next call to any of these methods
+  OpenTelemetry.error_handler = nil
+  OpenTelemetry.propagation = nil
+end

test/test_helpers/app_config.rb

@@ -0,0 +1,91 @@
+# frozen_string_literal: true
+
+# Copyright The OpenTelemetry Authors
+#
+# SPDX-License-Identifier: Apache-2.0
+
+class Application < Rails::Application; end
+require "action_controller/railtie"
+require_relative "middlewares"
+require_relative "controllers"
+require_relative "routes"
+
+module AppConfig
+  extend self
+
+  def initialize_app(use_exceptions_app: false, remove_rack_tracer_middleware: false)
+    new_app = Application.new
+    new_app.config.secret_key_base = "secret_key_base"
+
+    # Ensure we don't see this Rails warning when testing
+    new_app.config.eager_load = false
+
+    # Prevent tests from creating log/*.log
+    new_app.config.logger = Logger.new(File::NULL)
+
+    new_app.config.filter_parameters = [:param_to_be_filtered]
+
+    apply_rails_configs(new_app)
+
+    remove_rack_middleware(new_app) if remove_rack_tracer_middleware
+    add_exceptions_app(new_app) if use_exceptions_app
+    add_middlewares(new_app)
+
+    new_app.initialize!
+
+    draw_routes(new_app)
+
+    new_app
+  end
+
+  private
+
+  def remove_rack_middleware(application)
+    application.middleware.delete(
+      OpenTelemetry::Instrumentation::Rack::Middlewares::TracerMiddleware
+    )
+  end
+
+  def add_exceptions_app(application)
+    application.config.exceptions_app = lambda do |env|
+      ExceptionsController.action(:show).call(env)
+    end
+  end
+
+  def add_middlewares(application)
+    application.middleware.insert_after(
+      ActionDispatch::DebugExceptions,
+      ExceptionRaisingMiddleware
+    )
+
+    application.middleware.insert_after(
+      ActionDispatch::DebugExceptions,
+      RedirectMiddleware
+    )
+  end
+
+  def apply_rails_configs(application)
+    case Rails.version
+    when /^6\.1/
+      apply_rails_6_1_configs(application)
+    when /^7\./
+      apply_rails_7_configs(application)
+    end
+  end
+
+  def apply_rails_6_1_configs(application)
+    # Required in Rails 6
+    application.config.hosts << "example.org"
+  end
+
+  def apply_rails_7_configs(application)
+    # Required in Rails 7
+    application.config.hosts << "example.org"
+
+    # Unfreeze values which may have been frozen on previous initializations.
+    ActiveSupport::Dependencies.autoload_paths =
+      ActiveSupport::Dependencies.autoload_paths.dup
+    ActiveSupport::Dependencies.autoload_once_paths =
+      ActiveSupport::Dependencies.autoload_once_paths.dup
+  end
+end

test/test_helpers/controllers.rb

@@ -0,0 +1,8 @@
+# frozen_string_literal: true
+
+# Copyright The OpenTelemetry Authors
+#
+# SPDX-License-Identifier: Apache-2.0
+
+require_relative "controllers/example_controller"
+require_relative "controllers/exceptions_controller"

test/test_helpers/controllers/example_controller.rb

@@ -0,0 +1,17 @@
+# frozen_string_literal: true
+
+# Copyright The OpenTelemetry Authors
+#
+# SPDX-License-Identifier: Apache-2.0
+
+class ExampleController < ActionController::Base
+  include ::Rails.application.routes.url_helpers
+
+  def ok
+    render plain: "OK"
+  end
+
+  def internal_server_error
+    raise :internal_server_error
+  end
+end