Merge branch 'note-background-job' into 'master'

Background process note logic for #3948

Quick and dirty way to get *most* of the note processing out of band and into the background. Seeing some pretty nice speed bumps. Keep in mind that doing this in process results in slower and slower responses as more notes are added and more participants exist.

```
without background processing
  Completed 200 OK in 627ms (Views: 0.5ms | ActiveRecord: 32.3ms)
  Completed 200 OK in 478ms (Views: 0.8ms | ActiveRecord: 28.3ms)
  Completed 200 OK in 1107ms (Views: 0.6ms | ActiveRecord: 36.6ms)

with background processing
  Completed 200 OK in 108ms (Views: 0.6ms | ActiveRecord: 4.7ms)
  Completed 200 OK in 78ms (Views: 0.5ms | ActiveRecord: 4.5ms)
  Completed 200 OK in 164ms (Views: 0.5ms | ActiveRecord: 8.3ms)
```

As you can see, speeds are consistent when doing the harder work out of process. I'm not sure the number of sql queries we're saving, but based on the logs alone it's a pretty good amount.

@dzaporozhets @yorickpeterse I would love some input on this.

See merge request !2631

app/controllers/projects/notes_controller.rb

@@ -106,7 +106,7 @@ class Projects::NotesController < Projects::ApplicationController
           { notes_left: [note], notes_right: [] }
         else
           { notes_left: [], notes_right: [note] }
-       end
+        end
     else
       template = "projects/notes/_diff_notes_with_reply"
       locals = { notes: [note] }

app/services/notes/create_service.rb

@@ -6,27 +6,12 @@ module Notes
       note.system = false
 
       if note.save
-        notification_service.new_note(note)
-
-        # Skip system notes, like status changes and cross-references and awards
-        unless note.system || note.is_award
-          event_service.leave_note(note, note.author)
-          note.create_cross_references!
-          execute_hooks(note)
-        end
+        # Finish the harder work in the background
+        NewNoteWorker.perform_in(2.seconds, note.id, params)
       end
 
       note
     end
 
-    def hook_data(note)
-      Gitlab::NoteDataBuilder.build(note, current_user)
-    end
-
-    def execute_hooks(note)
-      note_data = hook_data(note)
-      note.project.execute_hooks(note_data, :note_hooks)
-      note.project.execute_services(note_data, :note_hooks)
-    end
   end
 end

app/services/notes/post_process_service.rb

+module Notes
+  class PostProcessService
+
+    attr_accessor :note
+
+    def initialize(note)
+      @note = note
+    end
+
+    def execute
+      # Skip system notes, like status changes and cross-references and awards
+      unless @note.system || @note.is_award
+        EventCreateService.new.leave_note(@note, @note.author)
+        @note.create_cross_references!
+        execute_note_hooks
+      end
+    end
+
+    def hook_data
+      Gitlab::NoteDataBuilder.build(@note, @note.author)
+    end
+
+    def execute_note_hooks
+      note_data = hook_data
+      @note.project.execute_hooks(note_data, :note_hooks)
+      @note.project.execute_services(note_data, :note_hooks)
+    end
+
+  end
+end

app/workers/new_note_worker.rb

+class NewNoteWorker
+  include Sidekiq::Worker
+
+  sidekiq_options queue: :default
+
+  def perform(note_id, note_params)
+    note = Note.find(note_id)
+
+    NotificationService.new.new_note(note)
+    Notes::PostProcessService.new(note).execute
+  end
+end

spec/services/notes/create_service_spec.rb

@@ -14,9 +14,7 @@ describe Notes::CreateService, services: true do
           noteable_type: 'Issue',
           noteable_id: issue.id
         }
-
-        expect(project).to receive(:execute_hooks)
-        expect(project).to receive(:execute_services)
+        
         @note = Notes::CreateService.new(project, user, opts).execute
       end
 

spec/services/notes/post_process_service_spec.rb

+require 'spec_helper'
+
+describe Notes::PostProcessService, services: true do
+  let(:project) { create(:empty_project) }
+  let(:issue) { create(:issue, project: project) }
+  let(:user) { create(:user) }
+
+  describe :execute do
+    before do
+      project.team << [user, :master]
+      note_opts = {
+        note: 'Awesome comment',
+        noteable_type: 'Issue',
+        noteable_id: issue.id
+      }
+
+      @note = Notes::CreateService.new(project, user, note_opts).execute
+    end
+
+    it do
+      expect(project).to receive(:execute_hooks)
+      expect(project).to receive(:execute_services)
+      Notes::PostProcessService.new(@note).execute
+    end
+  end
+end