Add Appsignal::Integrations::ActiveSupportEventReporter

Rails 8.1 adds ActiveSupport::EventReporter, an interface for
reporting structured events. To catch these, report them as info-level
logs in the rails_events category through the newly added
Appsignal::Integrations::ActiveSupportEventReporter.

Author: jeffkreeftmeijer

.changesets/report-events-from-rails-8-1-s-activesupport--eventreporter-as-logs.md

@@ -0,0 +1,6 @@
+---
+bump: minor
+type: add
+---
+
+Report events from Rails 8.1's ActiveSupport::EventReporter as logs

lib/appsignal/hooks.rb

@@ -79,6 +79,7 @@ def truncate(text)
 require "appsignal/hooks/action_mailer"
 require "appsignal/hooks/active_job"
 require "appsignal/hooks/active_support_notifications"
+require "appsignal/hooks/active_support_event_reporter"
 require "appsignal/hooks/celluloid"
 require "appsignal/hooks/code_ownership"
 require "appsignal/hooks/delayed_job"

lib/appsignal/hooks/active_support_event_reporter.rb

@@ -0,0 +1,19 @@
+# frozen_string_literal: true
+
+module Appsignal
+  class Hooks
+    # @!visibility private
+    class ActiveSupportEventReporterHook < Appsignal::Hooks::Hook
+      register :active_support_event_reporter
+
+      def dependencies_present?
+        defined?(::ActiveSupport::EventReporter)
+      end
+
+      def install
+        require "appsignal/integrations/active_support_event_reporter"
+        Rails.event.subscribe(Appsignal::Integrations::ActiveSupportEventReporter::Subscriber.new())
+      end
+    end
+  end
+end

lib/appsignal/integrations/active_support_event_reporter.rb

@@ -0,0 +1,18 @@
+# frozen_string_literal: true
+
+module Appsignal
+  module Integrations
+    # @!visibility private
+    module ActiveSupportEventReporter
+      class Subscriber
+        def initialize
+          @logger = Appsignal::Logger.new("rails_events")
+        end
+
+        def emit(event)
+          @logger.info(event[:name], event[:payload])
+        end
+      end
+    end
+  end
+end

spec/lib/appsignal/hooks/active_support_event_reporter_spec.rb

@@ -0,0 +1,53 @@
+describe Appsignal::Hooks::ActiveSupportEventReporterHook do
+  begin
+    require "active_support/event_reporter"
+  rescue LoadError
+  end
+
+  describe "#dependencies_present?" do
+    subject { described_class.new.dependencies_present? }
+
+    if DependencyHelper.rails8_1_present?
+      context "when ActiveSupport::EventReporter is present" do
+        it { is_expected.to be_truthy }
+      end
+    else
+      context "when ActiveSupport::EventReporter is not present" do
+        it { is_expected.to be_falsy }
+      end
+    end
+  end
+
+  if defined?(::ActiveSupport::EventReporter)
+    describe "#install" do
+      before do
+        # Mock Rails.event
+        stub_const("MockEventReporter", Class.new do
+          attr_reader :subscribers
+
+          def initialize
+            @subscribers = []
+          end
+
+          def subscribe(subscriber)
+            @subscribers << subscriber
+          end
+        end)
+
+        mock_event_reporter = MockEventReporter.new
+
+        allow(Rails).to receive(:event).and_return(mock_event_reporter)
+      end
+
+      it "subscribes the ActiveSupportEventReporter::Subscriber to Rails.event" do
+        event_reporter = Rails.event
+        expect(event_reporter.subscribers).to be_empty
+
+        described_class.new.install
+
+        expect(event_reporter.subscribers.length).to eq(1)
+        expect(event_reporter.subscribers.first).to be_a(Appsignal::Integrations::ActiveSupportEventReporter::Subscriber)
+      end
+    end
+  end
+end

spec/lib/appsignal/integrations/active_support_event_reporter_spec.rb

@@ -0,0 +1,24 @@
+require "appsignal/integrations/active_support_event_reporter"
+
+describe Appsignal::Integrations::ActiveSupportEventReporter::Subscriber do
+  let(:subscriber) { described_class.new }
+  let(:logger) { instance_double(Appsignal::Logger) }
+
+  before do
+    start_agent
+    allow(Appsignal::Logger).to receive(:new).with("rails_events").and_return(logger)
+  end
+
+  describe "#emit" do
+    it "logs the event name and payload" do
+      event = {
+        :name => "user.created",
+        :payload => { :id => 123, :email => "[email protected]" },
+      }
+
+      expect(logger).to receive(:info).with("user.created", { :id => 123, :email => "[email protected]" })
+
+      subscriber.emit(event)
+    end
+  end
+end

spec/support/helpers/dependency_helper.rb

@@ -49,6 +49,10 @@ def rails7_1_present?
     rails_present? && rails_version >= Gem::Version.new("7.1.0")
   end
 
+  def rails8_1_present?
+    rails_present? && rails_version >= Gem::Version.new("8.1.0")
+  end
+
   def active_job_wraps_args?
     rails7_present? || (ruby_3_1_or_newer? && rails6_1_present? && !rails6_1_5_present?)
   end