ActiveSupport notifications: allowlist event names

lib/new_relic/agent/configuration/default_source.rb

@@ -4,6 +4,7 @@
 
 require 'forwardable'
 require_relative '../../constants'
+require_relative '../instrumentation/active_support_subscriber'
 
 module NewRelic
   module Agent
@@ -1415,6 +1416,19 @@ def self.enforce_fallback(allowed_values: nil, fallback: nil)
           :description => 'Configures the TCP/IP port for the trace observer Host'
         },
         # Instrumentation
+        :'instrumentation.active_support_notifications.active_support_events' => {
+          :default => NewRelic::Agent::Instrumentation::ActiveSupportSubscriber::EVENT_NAME_TO_METHOD_NAME.keys,
+          :public => true,
+          :type => Array,
+          :allowed_from_server => false,
+          :description => <<~ACTIVE_SUPPORT_EVENTS.chomp.tr("\n", ' ')
+            An allowlist array of Active Support notifications events specific to the Active Support library
+            itself that the agent should subscribe to. The Active Support library specific events focus primarily
+            on caching. Any event name not included in this list will be ignored by the agent. Provide complete event
+            names such as 'cache_fetch_hit.active_support'. Do not provide asterisks or regex patterns, and do not
+            escape any characters with backslashes.
+          ACTIVE_SUPPORT_EVENTS
+        },
         :'instrumentation.active_support_broadcast_logger' => {
           :default => instrumentation_value_from_boolean(:'application_logging.enabled'),
           :documentation_default => 'auto',

lib/new_relic/agent/instrumentation/active_support.rb

@@ -7,6 +7,8 @@
 DependencyDetection.defer do
   named :active_support
 
+  EVENT_NAMES_PARAMETER = :'instrumentation.active_support_notifications.active_support_events'
+
   depends_on do
     !NewRelic::Agent.config[:disable_active_support]
   end
@@ -16,12 +18,17 @@
       !NewRelic::Agent::Instrumentation::ActiveSupportSubscriber.subscribed?
   end
 
+  depends_on do
+    !NewRelic::Agent.config[EVENT_NAMES_PARAMETER].empty?
+  end
+
   executes do
     NewRelic::Agent.logger.info('Installing ActiveSupport instrumentation')
   end
 
   executes do
-    ActiveSupport::Notifications.subscribe(/\.active_support$/,
+    event_names = NewRelic::Agent.config[EVENT_NAMES_PARAMETER].map { |n| Regexp.escape(n) }.join('|')
+    ActiveSupport::Notifications.subscribe(/\A(?:#{event_names})\z/,
       NewRelic::Agent::Instrumentation::ActiveSupportSubscriber.new)
   end
 end

lib/new_relic/agent/instrumentation/active_support_subscriber.rb

@@ -2,12 +2,25 @@
 # See https://github.com/newrelic/newrelic-ruby-agent/blob/main/LICENSE for complete details.
 # frozen_string_literal: true
 
-require 'new_relic/agent/instrumentation/notifications_subscriber'
+require_relative 'notifications_subscriber'
 
 module NewRelic
   module Agent
     module Instrumentation
       class ActiveSupportSubscriber < NotificationsSubscriber
+        EVENT_NAME_TO_METHOD_NAME = {
+          'cache_fetch_hit.active_support' => 'fetch_hit',
+          'cache_generate.active_support' => 'generate',
+          'cache_read.active_support' => 'read',
+          'cache_write.active_support' => 'write',
+          'cache_delete.active_support' => 'delete',
+          'cache_exist?.active_support' => 'exist?',
+          'cache_read_multi.active_support' => 'read_multi',
+          'cache_write_multi.active_support' => 'write_multi',
+          'cache_delete_multi.active_support' => 'delete_multi',
+          'message_serializer_fallback.active_support' => 'message_serializer_fallback'
+        }.freeze
+
         def add_segment_params(segment, payload)
           segment.params[:key] = payload[:key]
           segment.params[:store] = payload[:store]
@@ -18,23 +31,9 @@ def add_segment_params(segment, payload)
 
         def metric_name(name, payload)
           store = payload[:store]
-          method = method_from_name(name)
+          method = EVENT_NAME_TO_METHOD_NAME.fetch(name, name.delete_prefix('cache_').delete_suffix('.active_support'))
           "Ruby/ActiveSupport#{"/#{store}" if store}/#{method}"
         end
-
-        PATTERN = /\Acache_([^\.]*)\.active_support\z/
-
-        METHOD_NAME_MAPPING = Hash.new do |h, k|
-          if PATTERN =~ k
-            h[k] = $1
-          else
-            h[k] = NewRelic::UNKNOWN
-          end
-        end
-
-        def method_from_name(name)
-          METHOD_NAME_MAPPING[name]
-        end
       end
     end
   end

test/new_relic/agent/instrumentation/rails/active_support_subscriber.rb

@@ -75,11 +75,12 @@ def test_metric_recorded_for_new_event_names
         end
 
         def test_failsafe_if_event_does_not_match_expected_pattern
+          name = 'charcuterie_build_a_board_workshop'
           in_transaction('test') do
-            generate_event('charcuterie_build_a_board_workshop')
+            generate_event(name)
           end
 
-          assert_metrics_recorded "#{METRIC_PREFIX}#{DEFAULT_STORE}/Unknown"
+          assert_metrics_recorded "#{METRIC_PREFIX}#{DEFAULT_STORE}/#{name}"
         end
 
         def test_key_recorded_as_attribute_on_traces