Add tracers to methods called by action mailer

app/services/user_access_key.rb

@@ -9,8 +9,6 @@
 # Store F (User.encrypted_password) and D (User.encryption_key) in db
 
 class UserAccessKey
-  include ::NewRelic::Agent::MethodTracer
-
   attr_accessor :cost, :encrypted_d, :salt, :z1, :z2, :random_r
 
   def initialize(password:, salt:, cost: nil)
@@ -86,7 +84,6 @@ def build(password, pw_salt)
     self.z1, self.z2 = build_segments(scrypted)
     self.random_r = Pii::Cipher.random_key
   end
-  add_method_tracer :build, 'Custom/UserAccessKey/build'
 
   def build_segments(scrypted)
     hashed = SCrypt::Password.new(scrypted).digest

config/initializers/new_relic_tracers.rb

@@ -0,0 +1,47 @@
+## Add NR tracers to methods so we can trace execution in the NR dashboard
+## Ref: https://docs.newrelic.com/docs/agents/ruby-agent/api-guides/ruby-custom-instrumentation
+require 'new_relic/agent/method_tracer'
+require 'aws/ses'
+
+Aws::SES::Base.class_eval do
+  include ::NewRelic::Agent::MethodTracer
+  add_method_tracer :initialize, "Custom/#{name}/initialize"
+  add_method_tracer :deliver, "Custom/#{name}/deliver"
+  add_method_tracer :deliver!, "Custom/#{name}/deliver!"
+  add_method_tracer :ses_client, "Custom/#{name}/ses_client"
+end
+
+ConfirmationEmailPresenter.class_eval do
+  include ::NewRelic::Agent::MethodTracer
+  add_method_tracer :initialize, "Custom/#{name}/initialize"
+  add_method_tracer :first_sentence, "Custom/#{name}/first_sentence"
+  add_method_tracer :confirmation_period, "Custom/#{name}/confirmation_period"
+end
+
+CustomDeviseMailer.class_eval do
+  include ::NewRelic::Agent::MethodTracer
+  add_method_tracer :initialize, "Custom/#{name}/initialize"
+  add_method_tracer :confirmation_instructions, "Custom/#{name}/confirmation_instructions"
+  add_method_tracer :initialize_from_record, "Custom/#{name}/initialize_from_record"
+  add_method_tracer :mail, "Custom/#{name}/mail"
+end
+
+Mail::Message.class_eval do
+  include ::NewRelic::Agent::MethodTracer
+  add_method_tracer :initialize, "Custom/#{name}/initialize"
+  add_method_tracer :deliver, "Custom/#{name}/deliver"
+  add_method_tracer :deliver!, "Custom/#{name}/deliver!"
+end
+
+User.class_eval do
+  include ::NewRelic::Agent::MethodTracer
+  add_method_tracer :send_devise_notification, "Custom/#{name}/send_devise_notification"
+  add_method_tracer(
+    :send_custom_confirmation_instructions, "Custom/#{name}/send_custom_confirmation_instructions"
+  )
+end
+
+UserAccessKey.class_eval do
+  include ::NewRelic::Agent::MethodTracer
+  add_method_tracer :build, "Custom/#{name}/build"
+end