Don't send healthcheck events to AppSignal to save storage

Author: northeastprince

config/initializers/health_check_event_filter.rb

@@ -0,0 +1,32 @@
+class FilteredEventSubscriber
+  def initialize(subscriber, filter:)
+    @subscriber = subscriber
+    @filter = filter
+  end
+
+  def emit(event)
+    @subscriber.emit(event) if @filter.call(event)
+  end
+end
+
+class HealthCheckFilteredEventSubscriber < FilteredEventSubscriber
+  def initialize(subscriber)
+    filter = ->(event) { event.dig(:payload, :controller) != "Rails::HealthController" }
+
+    super(subscriber, filter:)
+  end
+end
+
+Rails.application.config.to_prepare do
+  next unless defined?(Appsignal::Integrations::ActiveSupportEventReporter::Subscriber)
+
+  subscribers = Rails.event.instance_variable_get(:@subscribers)
+  original = subscribers.find { it[:subscriber].is_a? Appsignal::Integrations::ActiveSupportEventReporter::Subscriber }
+
+  next unless original
+
+  subscribers.delete original
+
+  filtered = HealthCheckFilteredEventSubscriber.new(original[:subscriber])
+  Rails.event.subscribe(filtered, &original[:filter])
+end

test/lib/health_check_event_filtering_test.rb

@@ -0,0 +1,34 @@
+require "test_helper"
+
+class HealthCheckEventFilteringTest < ActionDispatch::IntegrationTest
+  test "filters out health check request events" do
+    with_filtered_event_reporter do
+      assert_no_event_reported("action_controller.request_started") do
+        get health_check_path
+        assert_response :ok
+      end
+    end
+  end
+
+  test "passes through non-health check request events" do
+    assert_event_reported("action_controller.request_completed") do
+      get root_path
+    end
+  end
+
+  private
+
+  def with_filtered_event_reporter
+    original = ActiveSupport.event_reporter
+    ActiveSupport.event_reporter = FilteredEventReporter.new(original)
+    yield
+  ensure
+    ActiveSupport.event_reporter = original
+  end
+
+  class FilteredEventReporter < SimpleDelegator
+    def subscribe(subscriber, &filter)
+      super(HealthCheckFilteredEventSubscriber.new(subscriber), &filter)
+    end
+  end
+end