feat: subscribe to process.action_mailer notifications

Author: mrsimo

instrumentation/action_mailer/README.md

@@ -21,7 +21,7 @@ To use the instrumentation, call `use` with the name of the instrumentation:
 
 ```ruby
 OpenTelemetry::SDK.configure do |c|
-  # Use only the ActionMailer instrumentation 
+  # Use only the ActionMailer instrumentation
   c.use 'OpenTelemetry::Instrumentation::ActionMailer'
   # Use the ActionMailer instrumentation along with the rest of the Rails-related instrumentation
   c.use 'OpenTelemetry::Instrumentation::Rails'
@@ -44,8 +44,8 @@ See the table below for details of what [Rails Framework Hook Events](https://gu
 
 | Event Name | Creates Span? | Notes |
 | - | - | - |
-| `deliver.action_mailer` | :white_check_mark: | Creates an span with kind `internal` and email content and status|
-| `process.action_mailer` | :x: | Lack of useful info so ignored |
+| `deliver.action_mailer` | :white_check_mark: | Creates a span with kind `internal` and email content and status |
+| `process.action_mailer` | :white_check_mark: | Creates a span with kind `internal` that will include email rendering spans |
 
 ### Options
 
@@ -67,9 +67,9 @@ end
 
 ## Semantic Conventions
 
-Internal spans are named using the name of the `ActiveSupport` event that was provided (e.g. `action_mailer deliver`).
+Internal spans are named using the name of the `ActiveSupport` event that was provided (e.g. `deliver.action_mailer`).
 
-The following attributes from the notification payload for the `deliver.action_mailer` event are attached to `action_mailer deliver` spans:
+The following attributes from the notification payload for the `deliver.action_mailer` event are attached:
 
 | Attribute Name | Type | Notes |
 | - | - | - |

instrumentation/action_mailer/lib/opentelemetry/instrumentation/action_mailer/instrumentation.rb

@@ -27,7 +27,9 @@ class Instrumentation < OpenTelemetry::Instrumentation::Base
         end
 
         option :disallowed_notification_payload_keys, default: [], validate: :array
+        option :disallowed_process_payload_keys,      default: [], validate: :array
         option :notification_payload_transform,       default: nil, validate: :callable
+        option :process_payload_transform,            default: nil, validate: :callable
         option :email_address,                        default: :omit, validate: %I[omit include]
 
         private

instrumentation/action_mailer/lib/opentelemetry/instrumentation/action_mailer/railtie.rb

@@ -7,24 +7,29 @@
 module OpenTelemetry
   module Instrumentation
     module ActionMailer
-      SUBSCRIPTIONS = %w[
-        deliver.action_mailer
-      ].freeze
+      DELIVER_SUBSCRIPTION = 'deliver.action_mailer'
+      PROCESS_SUBSCRIPTION = 'process.action_mailer'
 
       # This Railtie sets up subscriptions to relevant ActionMailer notifications
       class Railtie < ::Rails::Railtie
         config.after_initialize do
           ::OpenTelemetry::Instrumentation::ActiveSupport::Instrumentation.instance.install({})
 
-          SUBSCRIPTIONS.each do |subscription_name|
-            config = ActionMailer::Instrumentation.instance.config
-            ::OpenTelemetry::Instrumentation::ActiveSupport.subscribe(
-              ActionMailer::Instrumentation.instance.tracer,
-              subscription_name,
-              config[:notification_payload_transform],
-              config[:disallowed_notification_payload_keys]
-            )
-          end
+          config = ActionMailer::Instrumentation.instance.config
+
+          ::OpenTelemetry::Instrumentation::ActiveSupport.subscribe(
+            ActionMailer::Instrumentation.instance.tracer,
+            DELIVER_SUBSCRIPTION,
+            config[:notification_payload_transform],
+            config[:disallowed_notification_payload_keys]
+          )
+
+          ::OpenTelemetry::Instrumentation::ActiveSupport.subscribe(
+            ActionMailer::Instrumentation.instance.tracer,
+            PROCESS_SUBSCRIPTION,
+            config[:process_payload_transform],
+            config[:disallowed_process_payload_keys]
+          )
         end
       end
     end