fix: use AS::N subscriber for serialize events

instrumentation/active_model_serializers/example/rails_app.rb

@@ -0,0 +1,74 @@
+# frozen_string_literal: true
+
+# Copyright The OpenTelemetry Authors
+#
+# SPDX-License-Identifier: Apache-2.0
+
+require 'bundler/inline'
+
+gemfile(true) do
+  source 'https://rubygems.org'
+
+  gem 'rails'
+  gem 'active_model_serializers'
+  gem 'opentelemetry-api'
+  gem 'opentelemetry-common'
+  gem 'opentelemetry-instrumentation-active_model_serializers', path: '../'
+  gem 'opentelemetry-sdk'
+  gem 'opentelemetry-exporter-otlp'
+end
+
+ENV['OTEL_TRACES_EXPORTER'] ||= 'console'
+OpenTelemetry::SDK.configure do |c|
+  c.service_name = 'active_model_serializers_example'
+  c.use 'OpenTelemetry::Instrumentation::ActiveModelSerializers'
+end
+
+# no manual subscription trigger
+
+at_exit do
+  OpenTelemetry.tracer_provider.shutdown
+end
+
+# TraceRequestApp is a minimal Rails application inspired by the Rails
+# bug report template for Action Controller.
+# The configuration is compatible with Rails 6.0
+class TraceRequestApp < Rails::Application
+  config.root = __dir__
+  config.hosts << 'example.org'
+  credentials.secret_key_base = 'secret_key_base'
+
+  config.eager_load = false
+
+  config.logger = Logger.new($stdout)
+  Rails.logger  = config.logger
+end
+
+# Rails app initialization will pick up the instrumentation Railtie
+# and subscribe to Active Support notifications
+TraceRequestApp.initialize!
+
+ExampleAppTracer = OpenTelemetry.tracer_provider.tracer('example_app')
+
+class TestModel
+  include ActiveModel::API
+  include ActiveModel::Serialization
+
+  attr_accessor :name
+
+  def attributes
+    { 'name' => nil,
+      'screaming_name' => nil }
+  end
+
+  def screaming_name
+    ExampleAppTracer.in_span('screaming_name transform') do |span|
+      name.upcase
+    end
+  end
+end
+
+model = TestModel.new(name: 'test object')
+serialized_model = ActiveModelSerializers::SerializableResource.new(model).serializable_hash
+
+puts "\n*** The serialized object: #{serialized_model}"

instrumentation/active_model_serializers/example/standalone.rb

@@ -0,0 +1,57 @@
+# frozen_string_literal: true
+
+# Copyright The OpenTelemetry Authors
+#
+# SPDX-License-Identifier: Apache-2.0
+
+require 'bundler/inline'
+
+gemfile(true) do
+  source 'https://rubygems.org'
+
+  gem 'active_model_serializers'
+  gem 'opentelemetry-api'
+  gem 'opentelemetry-common'
+  gem 'opentelemetry-instrumentation-active_model_serializers', path: '../'
+  gem 'opentelemetry-sdk'
+  gem 'opentelemetry-exporter-otlp'
+end
+
+ENV['OTEL_TRACES_EXPORTER'] ||= 'console'
+OpenTelemetry::SDK.configure do |c|
+  c.service_name = 'active_model_serializers_example'
+  c.use_all
+end
+
+# without Rails and the Railtie automation, must manually trigger
+# instrumentation subscription after SDK is configured
+OpenTelemetry::Instrumentation::ActiveModelSerializers.subscribe
+
+at_exit do
+  OpenTelemetry.tracer_provider.shutdown
+end
+
+ExampleAppTracer = OpenTelemetry.tracer_provider.tracer('example_app')
+
+class TestModel
+  include ActiveModel::API
+  include ActiveModel::Serialization
+
+  attr_accessor :name
+
+  def attributes
+    { 'name' => nil,
+      'screaming_name' => nil }
+  end
+
+  def screaming_name
+    ExampleAppTracer.in_span('screaming_name transform') do |span|
+      name.upcase
+    end
+  end
+end
+
+model = TestModel.new(name: 'test object')
+serialized_model = ActiveModelSerializers::SerializableResource.new(model).serializable_hash
+
+puts "\n*** The serialized object: #{serialized_model}"

instrumentation/active_model_serializers/lib/opentelemetry/instrumentation/active_model_serializers/instrumentation.rb

@@ -4,16 +4,24 @@
 #
 # SPDX-License-Identifier: Apache-2.0
 
+require 'opentelemetry-instrumentation-active_support'
+
 module OpenTelemetry
   module Instrumentation
     module ActiveModelSerializers
       # Instrumentation class that detects and installs the ActiveModelSerializers instrumentation
       class Instrumentation < OpenTelemetry::Instrumentation::Base
+        # Minimum supported version of the `active_model_serializers` gem
         MINIMUM_VERSION = Gem::Version.new('0.10.0')
 
+        # ActiveSupport::Notification topics to which the instrumentation subscribes
+        SUBSCRIPTIONS = %w[
+          render.active_model_serializers
+        ].freeze
+
         install do |_config|
+          install_active_support_instrumenation
           require_dependencies
-          register_event_handler
         end
 
         present do
@@ -24,24 +32,39 @@ class Instrumentation < OpenTelemetry::Instrumentation::Base
           !defined?(::ActiveSupport::Notifications).nil? && gem_version >= MINIMUM_VERSION
         end
 
+        def subscribe
+          SUBSCRIPTIONS.each do |subscription_name|
+            OpenTelemetry.logger.debug("Subscribing to #{subscription_name} notifications with #{_tracer}")
+            OpenTelemetry::Instrumentation::ActiveSupport.subscribe(_tracer, subscription_name, default_attribute_transformer)
+          end
+        end
+
         private
 
+        def _tracer
+          self.class.instance.tracer
+        end
+
         def gem_version
           Gem::Version.new(::ActiveModel::Serializer::VERSION)
         end
 
-        def require_dependencies
-          require_relative 'event_handler'
+        def install_active_support_instrumenation
+          OpenTelemetry::Instrumentation::ActiveSupport::Instrumentation.instance.install({})
         end
 
-        def register_event_handler
-          ::ActiveSupport::Notifications.subscribe(event_name) do |_name, start, finish, _id, payload|
-            EventHandler.handle(start, finish, payload)
-          end
+        def require_dependencies
+          require_relative 'railtie'
         end
 
-        def event_name
-          'render.active_model_serializers'
+        def default_attribute_transformer
+          lambda { |payload|
+            {
+              'serializer.name' => payload[:serializer].name,
+              'serializer.renderer' => 'active_model_serializers',
+              'serializer.format' => payload[:adapter]&.class&.name || 'default'
+            }
+          }
         end
       end
     end

instrumentation/active_model_serializers/lib/opentelemetry/instrumentation/active_model_serializers/railtie.rb

@@ -0,0 +1,24 @@
+# frozen_string_literal: true
+
+# Copyright The OpenTelemetry Authors
+#
+# SPDX-License-Identifier: Apache-2.0
+
+module OpenTelemetry
+  module Instrumentation
+    module ActiveModelSerializers # :nodoc:
+      def self.subscribe
+        Instrumentation.instance.subscribe
+      end
+
+      if defined?(::Rails::Railtie)
+        # This Railtie sets up subscriptions to relevant ActiveModelSerializers notifications
+        class Railtie < ::Rails::Railtie
+          config.after_initialize do
+            ::OpenTelemetry::Instrumentation::ActiveModelSerializers.subscribe
+          end
+        end
+      end
+    end
+  end
+end

instrumentation/active_model_serializers/opentelemetry-instrumentation-active_model_serializers.gemspec

@@ -26,6 +26,7 @@ Gem::Specification.new do |spec|
   spec.required_ruby_version = '>= 3.0'
 
   spec.add_dependency 'opentelemetry-api', '~> 1.0'
+  spec.add_dependency 'opentelemetry-instrumentation-active_support', '>= 0.6.0'
   spec.add_dependency 'opentelemetry-instrumentation-base', '~> 0.22.1'
 
   spec.add_development_dependency 'active_model_serializers', '>= 0.10.0'

instrumentation/active_model_serializers/test/opentelemetry/instrumentation/active_model_serializers/event_handler_test.rb → instrumentation/active_model_serializers/test/opentelemetry/instrumentation/active_model_serializers/instrumentation_test.rb

@@ -7,16 +7,17 @@
 require_relative '../../../test_helper'
 
 # require instrumentation so we do not have to depend on the install hook being called
-require_relative '../../../../lib/opentelemetry/instrumentation/active_model_serializers/event_handler'
+require_relative '../../../../lib/opentelemetry/instrumentation/active_model_serializers/instrumentation'
 
-describe OpenTelemetry::Instrumentation::ActiveModelSerializers::EventHandler do
+describe OpenTelemetry::Instrumentation::ActiveModelSerializers::Instrumentation do
   let(:instrumentation) { OpenTelemetry::Instrumentation::ActiveModelSerializers::Instrumentation.instance }
   let(:exporter) { EXPORTER }
   let(:span) { exporter.finished_spans.first }
   let(:model) { TestHelper::Model.new(name: 'test object') }
 
   before do
     instrumentation.install
+    instrumentation.subscribe
     exporter.reset
 
     # this is currently a noop but this will future proof the test
@@ -38,7 +39,7 @@
       _(exporter.finished_spans.size).must_equal 1
 
       _(span).must_be_kind_of OpenTelemetry::SDK::Trace::SpanData
-      _(span.name).must_equal 'ModelSerializer render'
+      _(span.name).must_equal 'render.active_model_serializers'
       _(span.attributes['serializer.name']).must_equal 'TestHelper::ModelSerializer'
       _(span.attributes['serializer.renderer']).must_equal 'active_model_serializers'
       _(span.attributes['serializer.format']).must_equal 'ActiveModelSerializers::Adapter::Attributes'
@@ -54,7 +55,7 @@
       _(exporter.finished_spans.size).must_equal 1
 
       _(span).must_be_kind_of OpenTelemetry::SDK::Trace::SpanData
-      _(span.name).must_equal 'ModelSerializer render'
+      _(span.name).must_equal 'render.active_model_serializers'
       _(span.attributes['serializer.name']).must_equal 'TestHelper::ModelSerializer'
       _(span.attributes['serializer.renderer']).must_equal 'active_model_serializers'
       _(span.attributes['serializer.format']).must_equal 'TestHelper::Model'

instrumentation/active_model_serializers/test/opentelemetry/instrumentation/active_model_serializers_test.rb

@@ -37,11 +37,15 @@
     end
   end
 
-  describe 'install' do
+  describe 'subscribe' do
+    before do
+      instrumentation.subscribe
+    end
+
     it 'subscribes to ActiveSupport::Notifications' do
       subscriptions = ActiveSupport::Notifications.notifier.instance_variable_get(:@string_subscribers)
       subscriptions = subscriptions['render.active_model_serializers']
-      assert(subscriptions.detect { |s| s.is_a?(ActiveSupport::Notifications::Fanout::Subscribers::Timed) })
+      assert(subscriptions.detect { |s| s.is_a?(ActiveSupport::Notifications::Fanout::Subscribers::Evented) })
     end
   end
 end