Improve `api/v1/markers#create` performance against simultaneous requests (#28718)

app/controllers/api/v1/markers_controller.rb

@@ -19,7 +19,7 @@ class Api::V1::MarkersController < Api::BaseController
       @markers = {}
 
       resource_params.each_pair do |timeline, timeline_params|
-        @markers[timeline] = current_user.markers.find_or_initialize_by(timeline: timeline)
+        @markers[timeline] = current_user.markers.find_or_create_by(timeline: timeline)
         @markers[timeline].update!(timeline_params)
       end
     end

spec/requests/api/v1/markers_spec.rb

@@ -2,20 +2,18 @@
 
 require 'rails_helper'
 
-RSpec.describe Api::V1::MarkersController do
-  render_views
+RSpec.describe 'API Markers' do
+  let(:user)    { Fabricate(:user) }
+  let(:scopes)  { 'read:statuses write:statuses' }
+  let(:token)   { Fabricate(:accessible_access_token, resource_owner_id: user.id, scopes: scopes) }
+  let(:headers) { { 'Authorization' => "Bearer #{token.token}" } }
 
-  let!(:user)  { Fabricate(:user) }
-  let!(:token) { Fabricate(:accessible_access_token, resource_owner_id: user.id, scopes: 'read:statuses write:statuses') }
-
-  before { allow(controller).to receive(:doorkeeper_token) { token } }
-
-  describe 'GET #index' do
+  describe 'GET /api/v1/markers' do
     before do
       Fabricate(:marker, timeline: 'home', last_read_id: 123, user: user)
       Fabricate(:marker, timeline: 'notifications', last_read_id: 456, user: user)
 
-      get :index, params: { timeline: %w(home notifications) }
+      get '/api/v1/markers', headers: headers, params: { timeline: %w(home notifications) }
     end
 
     it 'returns markers', :aggregate_failures do
@@ -29,10 +27,10 @@ RSpec.describe Api::V1::MarkersController do
     end
   end
 
-  describe 'POST #create' do
+  describe 'POST /api/v1/markers' do
     context 'when no marker exists' do
       before do
-        post :create, params: { home: { last_read_id: '69420' } }
+        post '/api/v1/markers', headers: headers, params: { home: { last_read_id: '69420' } }
       end
 
       it 'creates a marker', :aggregate_failures do
@@ -44,8 +42,8 @@ RSpec.describe Api::V1::MarkersController do
 
     context 'when a marker exists' do
       before do
-        post :create, params: { home: { last_read_id: '69420' } }
-        post :create, params: { home: { last_read_id: '70120' } }
+        post '/api/v1/markers', headers: headers, params: { home: { last_read_id: '69420' } }
+        post '/api/v1/markers', headers: headers, params: { home: { last_read_id: '70120' } }
       end
 
       it 'updates a marker', :aggregate_failures do