Merge branch 'feature/gb/email-delivery-metrics' into 'master'

Add emails delivery metrics

Closes #49214

See merge request gitlab-org/gitlab-ce!20638

changelogs/unreleased/feature-gb-email-delivery-metrics.yml

+---
+title: Add emails delivery Prometheus metrics
+merge_request: 20638
+author:
+type: added

config/initializers/action_mailer_hooks.rb

+unless Gitlab.config.gitlab.email_enabled
+  ActionMailer::Base.register_interceptor(::Gitlab::Email::Hook::DisableEmailInterceptor)
+  ActionMailer::Base.logger = nil
+end
+
+ActionMailer::Base.register_interceptors(
+  ::Gitlab::Email::Hook::AdditionalHeadersInterceptor,
+  ::Gitlab::Email::Hook::EmailTemplateInterceptor,
+  ::Gitlab::Email::Hook::DeliveryMetricsObserver
+)
+
+ActionMailer::Base.register_observer(::Gitlab::Email::Hook::DeliveryMetricsObserver)

config/initializers/additional_headers_interceptor.rb

-ActionMailer::Base.register_interceptor(AdditionalEmailHeadersInterceptor)

config/initializers/disable_email_interceptor.rb

-# Interceptor in lib/disable_email_interceptor.rb
-unless Gitlab.config.gitlab.email_enabled
-  ActionMailer::Base.register_interceptor(DisableEmailInterceptor)
-  ActionMailer::Base.logger = nil
-end

config/initializers/email_template_interceptor.rb

-# Interceptor in lib/email_template_interceptor.rb
-ActionMailer::Base.register_interceptor(EmailTemplateInterceptor)

lib/additional_email_headers_interceptor.rb

-class AdditionalEmailHeadersInterceptor
-  def self.delivering_email(message)
-    message.header['Auto-Submitted'] ||= 'auto-generated'
-    message.header['X-Auto-Response-Suppress'] ||= 'All'
-  end
-end

lib/disable_email_interceptor.rb

-# Read about interceptors in http://guides.rubyonrails.org/action_mailer_basics.html#intercepting-emails
-class DisableEmailInterceptor
-  def self.delivering_email(message)
-    message.perform_deliveries = false
-    Rails.logger.info "Emails disabled! Interceptor prevented sending mail #{message.subject}"
-  end
-end

lib/email_template_interceptor.rb

-# Read about interceptors in http://guides.rubyonrails.org/action_mailer_basics.html#intercepting-emails
-class EmailTemplateInterceptor
-  def self.delivering_email(message)
-    # Remove HTML part if HTML emails are disabled.
-    unless Gitlab::CurrentSettings.html_emails_enabled
-      message.parts.delete_if do |part|
-        part.content_type.start_with?('text/html')
-      end
-    end
-  end
-end

lib/gitlab/email/hook/additional_headers_interceptor.rb

+module Gitlab
+  module Email
+    module Hook
+      class AdditionalHeadersInterceptor
+        def self.delivering_email(message)
+          message.header['Auto-Submitted'] ||= 'auto-generated'
+          message.header['X-Auto-Response-Suppress'] ||= 'All'
+        end
+      end
+    end
+  end
+end

lib/gitlab/email/hook/delivery_metrics_observer.rb

+module Gitlab
+  module Email
+    module Hook
+      class DeliveryMetricsObserver
+        extend Gitlab::Utils::StrongMemoize
+
+        def self.delivering_email(_message)
+          delivery_attempts_counter.increment
+        end
+
+        def self.delivered_email(_message)
+          delivered_emails_counter.increment
+        end
+
+        def self.delivery_attempts_counter
+          strong_memoize(:delivery_attempts_counter) do
+            Gitlab::Metrics.counter(:gitlab_emails_delivery_attempts_total,
+                                    'Counter of total emails delivery attempts')
+          end
+        end
+
+        def self.delivered_emails_counter
+          strong_memoize(:delivered_emails_counter) do
+            Gitlab::Metrics.counter(:gitlab_emails_delivered_total,
+                                    'Counter of total emails delievered')
+          end
+        end
+      end
+    end
+  end
+end

lib/gitlab/email/hook/disable_email_interceptor.rb

+module Gitlab
+  module Email
+    module Hook
+      class DisableEmailInterceptor
+        def self.delivering_email(message)
+          message.perform_deliveries = false
+
+          Rails.logger.info "Emails disabled! Interceptor prevented sending mail #{message.subject}"
+        end
+      end
+    end
+  end
+end

lib/gitlab/email/hook/email_template_interceptor.rb

+module Gitlab
+  module Email
+    module Hook
+      class EmailTemplateInterceptor
+        ##
+        # Remove HTML part if HTML emails are disabled.
+        #
+        def self.delivering_email(message)
+          unless Gitlab::CurrentSettings.html_emails_enabled
+            message.parts.delete_if do |part|
+              part.content_type.start_with?('text/html')
+            end
+          end
+        end
+      end
+    end
+  end
+end

spec/lib/additional_email_headers_interceptor_spec.rb → spec/lib/gitlab/email/hook/additional_headers_interceptor_spec.rb

 require 'spec_helper'
 
-describe AdditionalEmailHeadersInterceptor do
+describe Gitlab::Email::Hook::AdditionalHeadersInterceptor do
   let(:mail) do
     ActionMailer::Base.mail(to: 'test@mail.com', from: 'info@mail.com', body: 'hello')
   end

spec/lib/gitlab/email/hook/delivery_metrics_observer_spec.rb

+require 'spec_helper'
+
+describe Gitlab::Email::Hook::DeliveryMetricsObserver do
+  let(:email) do
+    ActionMailer::Base.mail(to: 'test@example.com',
+                            from: 'info@example.com',
+                            body: 'hello')
+  end
+
+  context 'when email has been delivered' do
+    it 'increments both email delivery metrics' do
+      expect(described_class.delivery_attempts_counter).to receive(:increment)
+      expect(described_class.delivered_emails_counter).to receive(:increment)
+
+      email.deliver_now
+    end
+  end
+
+  context 'when email has not been delivered due to an error' do
+    before do
+      allow(email.delivery_method).to receive(:deliver!)
+        .and_raise(StandardError, 'Some SMTP error')
+    end
+
+    it 'increments only delivery attempt metric' do
+      expect(described_class.delivery_attempts_counter)
+        .to receive(:increment)
+      expect(described_class.delivered_emails_counter)
+        .not_to receive(:increment)
+
+      expect { email.deliver_now }
+        .to raise_error(StandardError, 'Some SMTP error')
+    end
+  end
+end

spec/lib/disable_email_interceptor_spec.rb → spec/lib/gitlab/email/hook/disable_email_interceptor_spec.rb

 require 'spec_helper'
 
-describe DisableEmailInterceptor do
+describe Gitlab::Email::Hook::DisableEmailInterceptor do
   before do
     Mail.register_interceptor(described_class)
   end

spec/mailers/notify_spec.rb

@@ -1366,7 +1366,8 @@ describe Notify do
       it 'only sends the text template' do
         stub_application_setting(html_emails_enabled: false)
 
-        EmailTemplateInterceptor.delivering_email(multipart_mail)
+        Gitlab::Email::Hook::EmailTemplateInterceptor
+          .delivering_email(multipart_mail)
 
         expect(multipart_mail).to have_part_with('text/plain')
         expect(multipart_mail).not_to have_part_with('text/html')
@@ -1377,7 +1378,8 @@ describe Notify do
       it 'sends a multipart message' do
         stub_application_setting(html_emails_enabled: true)
 
-        EmailTemplateInterceptor.delivering_email(multipart_mail)
+        Gitlab::Email::Hook::EmailTemplateInterceptor
+          .delivering_email(multipart_mail)
 
         expect(multipart_mail).to have_part_with('text/plain')
         expect(multipart_mail).to have_part_with('text/html')