Merge branch 'handle-smtp-input-errors' into 'master'

Gracefully handle SMTP user input errors (e.g. incorrect email addresses) to prevent Sidekiq retries

### What does this MR do?

This MR gracefully handles SMTP input errors (e.g. incorrect or invalid e-mail addresses) to prevent these types of exceptions from causing Sidekiq to retry the task. If these specific exceptions occur, they will be logged, and the e-mail will be dropped from the queue.

### Why was this MR needed?

If you include an author that has a misspelled e-mail address, Sidekiq will keep sending e-mail to all the recipients even if they have already received the e-mail. The only way to recover is to clear the Sidekiq queue.

Note that other exceptions can still be thrown (e.g. `IOError`, `Net::SMTPAuthenticationError`, `Net::SMTPServerBusy`, `Net::SMTPUnknownError`, and `TimeoutError`). If the worker encounters these, Sidekiq should retry the task.

### What are the relevant issue numbers?

Closes https://github.com/gitlabhq/gitlabhq/issues/9560

See merge request !1163

CHANGELOG

@@ -13,6 +13,7 @@ v 8.0.0 (unreleased)
   - Search for comments should be case insensetive
   - Create cross-reference for closing references on commits pushed to non-default branches (Maël Valais)
   - Ability to search milestones
+  - Gracefully handle SMTP user input errors (e.g. incorrect email addresses) to prevent Sidekiq retries (Stan Hu)
 
 v 7.14.1 (unreleased)
   - Only include base URL in OmniAuth full_host parameter (Stan Hu)

app/workers/emails_on_push_worker.rb

@@ -42,6 +42,7 @@ class EmailsOnPushWorker
     end
 
     recipients.split(" ").each do |recipient|
+      begin
         Notify.repository_push_email(
           project_id,
           recipient,
@@ -53,6 +54,10 @@ class EmailsOnPushWorker
           send_from_committer_email:  send_from_committer_email,
           disable_diffs:              disable_diffs
         ).deliver
+      # These are input errors and won't be corrected even if Sidekiq retries
+      rescue Net::SMTPFatalError, Net::SMTPSyntaxError => e
+        logger.info("Failed to send e-mail for project '#{project.name_with_namespace}' to #{recipient}: #{e}")
+      end
     end
   ensure
     compare = nil

spec/workers/emails_on_push_worker_spec.rb

+require 'spec_helper'
+
+describe EmailsOnPushWorker do
+  include RepoHelpers
+
+  let(:project) { create(:project) }
+  let(:user) { create(:user) }
+  let(:data) { Gitlab::PushDataBuilder.build_sample(project, user) }
+
+  subject { EmailsOnPushWorker.new }
+
+  before do
+    allow(Project).to receive(:find).and_return(project)
+  end
+
+  describe "#perform" do
+    it "sends mail" do
+      subject.perform(project.id, user.email, data.stringify_keys)
+
+      email = ActionMailer::Base.deliveries.last
+      expect(email.subject).to include('Change some files')
+      expect(email.to).to eq([user.email])
+    end
+
+    it "gracefully handles an input SMTP error" do
+      ActionMailer::Base.deliveries.clear
+      allow(Notify).to receive(:repository_push_email).and_raise(Net::SMTPFatalError)
+
+      subject.perform(project.id, user.email, data.stringify_keys)
+
+      expect(ActionMailer::Base.deliveries.count).to eq(0)
+    end
+  end
+end