Filter out old notes in NotesFinder

app/finders/notes_finder.rb

 class NotesFinder
+  FETCH_OVERLAP = 5.seconds
+
   def execute(project, current_user, params)
     target_type = params[:target_type]
     target_id   = params[:target_id]
-    case target_type
+    last_fetched_at = params.fetch(:last_fetched_at)
+    notes = case target_type
     when "commit"
       project.notes.for_commit_id(target_id).not_inline.fresh
     when "issue"
@@ -15,5 +18,8 @@ class NotesFinder
     else
       raise 'invalid target_type'
     end
+
+    # Use overlapping intervals to avoid worrying about race conditions
+    notes.where('updated_at > ?', last_fetched_at - FETCH_OVERLAP)
   end
 end

spec/finders/notes_finder_spec.rb

@@ -27,5 +27,12 @@ describe NotesFinder do
       params = { target_id: commit.id, target_type: 'invalid' }
       expect { NotesFinder.new.execute(project, user, params) }.to raise_error('invalid target_type')
     end
+
+    it 'filters out old notes' do
+      note2.update_attribute(:updated_at, 2.hours.ago)
+      params = { target_id: commit.id, target_type: 'commit', last_fetched_at: 1.hour.ago }
+      notes = NotesFinder.new.execute(project, user, params)
+      notes.should eq([note1])
+    end
   end
 end