Instrument the generation of Action Mailer messages

The processing of outbound mail is instrumented with the key
`process.action_mailer`. The payload includes the mailer name as well as
the mailer method.

2 files changed, 18 insertions, 4 deletions

diff --git a/actionmailer/lib/action_mailer/base.rb b/actionmailer/lib/action_mailer/base.rb
index ada86fbc4f..6357805198 100644
--- a/actionmailer/lib/action_mailer/base.rb
+++ b/actionmailer/lib/action_mailer/base.rb
@@ -511,11 +511,18 @@ module ActionMailer
       process(method_name, *args) if method_name
     end
 
-    def process(*args) #:nodoc:
-      lookup_context.skip_default_locale!
+    def process(method_name, *args) #:nodoc:
+      payload = {
+        :mailer => self.class.name,
+        :action => method_name
+      }
 
-      super
-      @_message = NullMail.new unless @_mail_was_called
+      ActiveSupport::Notifications.instrument("process.action_mailer", payload) do
+        lookup_context.skip_default_locale!
+
+        super
+        @_message = NullMail.new unless @_mail_was_called
+      end
     end
 
     class NullMail #:nodoc:
diff --git a/actionmailer/lib/action_mailer/log_subscriber.rb b/actionmailer/lib/action_mailer/log_subscriber.rb
index 8467d45986..eb6fb11d81 100644
--- a/actionmailer/lib/action_mailer/log_subscriber.rb
+++ b/actionmailer/lib/action_mailer/log_subscriber.rb
@@ -19,6 +19,13 @@ module ActionMailer
       debug(event.payload[:mail])
     end
 
+    # An email was generated.
+    def process(event)
+      mailer = event.payload[:mailer]
+      action = event.payload[:action]
+      debug("\n#{mailer}##{action}: processed outbound mail in #{event.duration.round(1)}ms")
+    end
+
     # Use the logger configured for ActionMailer::Base
     def logger
       ActionMailer::Base.logger