Merge branch '29010-perf-bar' into 'master'

Add an optional performance bar to view performance metrics for the current page

Closes #29010

See merge request !11439

27 files changed, 771 insertions, 2 deletions

diff --git a/Gemfile b/Gemfile
index 2de00bfc0a1..2c200f2fa7a 100644
--- a/Gemfile
+++ b/Gemfile
@@ -264,6 +264,17 @@ gem 'gettext_i18n_rails', '~> 1.8.0'
 gem 'gettext_i18n_rails_js', '~> 1.2.0'
 gem 'gettext', '~> 3.2.2', require: false, group: :development
 
+# Perf bar
+gem 'peek', '~> 1.0.1'
+gem 'peek-gc', '~> 0.0.2'
+gem 'peek-host', '~> 1.0.0'
+gem 'peek-mysql2', '~> 1.1.0', group: :mysql
+gem 'peek-performance_bar', '~> 1.2.1'
+gem 'peek-pg', '~> 1.3.0', group: :postgres
+gem 'peek-rblineprof', '~> 0.2.0'
+gem 'peek-redis', '~> 1.2.0'
+gem 'peek-sidekiq', '~> 1.0.3'
+
 # Metrics
 group :metrics do
   gem 'allocations', '~> 1.0', require: false, platform: :mri
diff --git a/Gemfile.lock b/Gemfile.lock
index a898c12485e..6755c75e331 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -56,6 +56,7 @@ GEM
     asciidoctor-plantuml (0.0.7)
       asciidoctor (~> 1.5)
     ast (2.3.0)
+    atomic (1.1.99)
     attr_encrypted (3.0.3)
       encryptor (~> 3.0.0)
     attr_required (1.0.0)
@@ -131,6 +132,8 @@ GEM
     coffee-script-source (1.10.0)
     colorize (0.7.7)
     concurrent-ruby (1.0.5)
+    concurrent-ruby-ext (1.0.5)
+      concurrent-ruby (= 1.0.5)
     connection_pool (2.2.1)
     crack (0.4.3)
       safe_yaml (~> 1.0.0)
@@ -548,6 +551,36 @@ GEM
     parser (2.4.0.0)
       ast (~> 2.2)
     path_expander (1.0.1)
+    peek (1.0.1)
+      concurrent-ruby (>= 0.9.0)
+      concurrent-ruby-ext (>= 0.9.0)
+      railties (>= 4.0.0)
+    peek-gc (0.0.2)
+      peek
+    peek-host (1.0.0)
+      peek
+    peek-mysql2 (1.1.0)
+      atomic (>= 1.0.0)
+      mysql2
+      peek
+    peek-performance_bar (1.2.1)
+      peek (>= 0.1.0)
+    peek-pg (1.3.0)
+      concurrent-ruby
+      concurrent-ruby-ext
+      peek
+      pg
+    peek-rblineprof (0.2.0)
+      peek
+      rblineprof
+    peek-redis (1.2.0)
+      atomic (>= 1.0.0)
+      peek
+      redis
+    peek-sidekiq (1.0.3)
+      atomic (>= 1.0.0)
+      peek
+      sidekiq
     pg (0.18.4)
     po_to_json (1.0.1)
       json (>= 1.6.0)
@@ -999,6 +1032,15 @@ DEPENDENCIES
   omniauth_crowd (~> 2.2.0)
   org-ruby (~> 0.9.12)
   paranoia (~> 2.2)
+  peek (~> 1.0.1)
+  peek-gc (~> 0.0.2)
+  peek-host (~> 1.0.0)
+  peek-mysql2 (~> 1.1.0)
+  peek-performance_bar (~> 1.2.1)
+  peek-pg (~> 1.3.0)
+  peek-rblineprof (~> 0.2.0)
+  peek-redis (~> 1.2.0)
+  peek-sidekiq (~> 1.0.3)
   pg (~> 0.18.2)
   poltergeist (~> 1.9.0)
   premailer-rails (~> 1.9.0)
diff --git a/app/assets/javascripts/peek.js b/app/assets/javascripts/peek.js
new file mode 100644
index 00000000000..de1a99fa3bd
--- /dev/null
+++ b/app/assets/javascripts/peek.js
@@ -0,0 +1,16 @@
+import 'vendor/peek';
+import 'vendor/peek.performance_bar';
+
+$(document).on('click', '#peek-show-queries', (e) => {
+  e.preventDefault();
+  $('.peek-rblineprof-modal').hide();
+  const $modal = $('#modal-peek-pg-queries');
+  if ($modal.length) {
+    $modal.modal('toggle');
+  }
+});
+
+$(document).on('click', '.js-lineprof-file', (e) => {
+  e.preventDefault();
+  $(e.target).parents('.peek-rblineprof-file').find('.data').toggle();
+});
diff --git a/app/assets/javascripts/shortcuts.js b/app/assets/javascripts/shortcuts.js
index 8ac71797c14..a4a7f3fa944 100644
--- a/app/assets/javascripts/shortcuts.js
+++ b/app/assets/javascripts/shortcuts.js
@@ -1,6 +1,8 @@
 /* eslint-disable func-names, space-before-function-paren, no-var, prefer-rest-params, wrap-iife, quotes, prefer-arrow-callback, consistent-return, object-shorthand, no-unused-vars, one-var, one-var-declaration-per-line, no-else-return, comma-dangle, max-len */
 /* global Mousetrap */
 /* global findFileURL */
+import Cookies from 'js-cookie';
+
 import findAndFollowLink from './shortcuts_dashboard_navigation';
 
 (function() {
@@ -14,6 +16,7 @@ import findAndFollowLink from './shortcuts_dashboard_navigation';
       Mousetrap.bind('?', this.onToggleHelp);
       Mousetrap.bind('s', Shortcuts.focusSearch);
       Mousetrap.bind('f', (e => this.focusFilter(e)));
+      Mousetrap.bind('p b', this.onTogglePerfBar);
 
       const $globalDropdownMenu = $('.global-dropdown-menu');
       const $globalDropdownToggle = $('.global-dropdown-toggle');
@@ -53,6 +56,17 @@ import findAndFollowLink from './shortcuts_dashboard_navigation';
       return Shortcuts.toggleHelp(this.enabledHelp);
     };
 
+    Shortcuts.prototype.onTogglePerfBar = function(e) {
+      e.preventDefault();
+      const performanceBarCookieName = 'perf_bar_enabled';
+      if (Cookies.get(performanceBarCookieName) === 'true') {
+        Cookies.remove(performanceBarCookieName, { path: '/' });
+      } else {
+        Cookies.set(performanceBarCookieName, true, { path: '/' });
+      }
+      gl.utils.refreshCurrentPage();
+    };
+
     Shortcuts.prototype.toggleMarkdownPreview = function(e) {
       // Check if short-cut was triggered while in Write Mode
       const $target = $(e.target);
diff --git a/app/controllers/application_controller.rb b/app/controllers/application_controller.rb
index 47ce21d238b..91694ebcd1d 100644
--- a/app/controllers/application_controller.rb
+++ b/app/controllers/application_controller.rb
@@ -9,6 +9,7 @@ class ApplicationController < ActionController::Base
   include SentryHelper
   include WorkhorseHelper
   include EnforcesTwoFactorAuthentication
+  include Peek::Rblineprof::CustomControllerHelpers
 
   before_action :authenticate_user_from_private_token!
   before_action :authenticate_user_from_rss_token!
@@ -18,7 +19,7 @@ class ApplicationController < ActionController::Base
   before_action :ldap_security_check
   before_action :sentry_context
   before_action :default_headers
-  before_action :add_gon_variables
+  before_action :add_gon_variables, unless: -> { request.path.start_with?('/-/peek') }
   before_action :configure_permitted_parameters, if: :devise_controller?
   before_action :require_email, unless: :devise_controller?
 
@@ -63,6 +64,21 @@ class ApplicationController < ActionController::Base
     end
   end
 
+  def peek_enabled?
+    return false unless Gitlab::PerformanceBar.enabled?
+    return false unless current_user
+
+    if RequestStore.active?
+      if RequestStore.store.key?(:peek_enabled)
+        RequestStore.store[:peek_enabled]
+      else
+        RequestStore.store[:peek_enabled] = cookies[:perf_bar_enabled].present?
+      end
+    else
+      cookies[:perf_bar_enabled].present?
+    end
+  end
+
   protected
 
   # This filter handles both private tokens and personal access tokens
diff --git a/app/helpers/nav_helper.rb b/app/helpers/nav_helper.rb
index 88dfe78c90c..833d3c36b28 100644
--- a/app/helpers/nav_helper.rb
+++ b/app/helpers/nav_helper.rb
@@ -27,6 +27,7 @@ module NavHelper
   def nav_header_class
     class_name = ''
     class_name << " with-horizontal-nav" if defined?(nav) && nav
+    class_name << " with-peek" if peek_enabled?
 
     class_name
   end
diff --git a/app/views/help/_shortcuts.html.haml b/app/views/help/_shortcuts.html.haml
index ea8bbe92d86..331d1181220 100644
--- a/app/views/help/_shortcuts.html.haml
+++ b/app/views/help/_shortcuts.html.haml
@@ -29,6 +29,10 @@
                   %td Focus Filter
                 %tr
                   %td.shortcut
+                    .key p b
+                  %td Show/hide the Performance Bar
+                %tr
+                  %td.shortcut
                     .key ?
                   %td Show/hide this dialog
                 %tr
diff --git a/app/views/layouts/_head.html.haml b/app/views/layouts/_head.html.haml
index 1ef0d524dbb..eea33b5966f 100644
--- a/app/views/layouts/_head.html.haml
+++ b/app/views/layouts/_head.html.haml
@@ -28,6 +28,7 @@
   = stylesheet_link_tag "application", media: "all"
   = stylesheet_link_tag "print",       media: "print"
   = stylesheet_link_tag "test",        media: "all" if Rails.env.test?
+  = stylesheet_link_tag 'peek' if peek_enabled?
 
   = Gon::Base.render_data
 
@@ -37,6 +38,7 @@
   = webpack_bundle_tag "main"
   = webpack_bundle_tag "raven" if current_application_settings.clientside_sentry_enabled
   = webpack_bundle_tag "test" if Rails.env.test?
+  = webpack_bundle_tag 'peek' if peek_enabled?
 
   - if content_for?(:page_specific_javascripts)
     = yield :page_specific_javascripts
diff --git a/app/views/layouts/application.html.haml b/app/views/layouts/application.html.haml
index 03688e9ff21..2b07273a0a8 100644
--- a/app/views/layouts/application.html.haml
+++ b/app/views/layouts/application.html.haml
@@ -3,6 +3,7 @@
   = render "layouts/head"
   %body{ class: @body_class, data: { page: body_data_page, project: "#{@project.path if @project}", group: "#{@group.path if @group}" } }
     = render "layouts/init_auto_complete" if @gfm_form
+    = render 'peek/bar'
     = render "layouts/header/default", title: header_title
     = render 'layouts/page', sidebar: sidebar, nav: nav
 
diff --git a/app/views/peek/views/_mysql2.html.haml b/app/views/peek/views/_mysql2.html.haml
new file mode 100644
index 00000000000..ac811a10ef5
--- /dev/null
+++ b/app/views/peek/views/_mysql2.html.haml
@@ -0,0 +1,4 @@
+- local_assigns.fetch(:view)
+
+= render 'peek/views/sql', view: view
+mysql
diff --git a/app/views/peek/views/_pg.html.haml b/app/views/peek/views/_pg.html.haml
new file mode 100644
index 00000000000..ee94c2f3274
--- /dev/null
+++ b/app/views/peek/views/_pg.html.haml
@@ -0,0 +1,4 @@
+- local_assigns.fetch(:view)
+
+= render 'peek/views/sql', view: view
+pg
diff --git a/app/views/peek/views/_sql.html.haml b/app/views/peek/views/_sql.html.haml
new file mode 100644
index 00000000000..16fc010f66f
--- /dev/null
+++ b/app/views/peek/views/_sql.html.haml
@@ -0,0 +1,13 @@
+%strong
+  %a#peek-show-queries{ href: '#' }
+    %span{ data: { defer_to: "#{view.defer_key}-duration" } }...
+    \/
+    %span{ data: { defer_to: "#{view.defer_key}-calls" } }...
+#modal-peek-pg-queries.modal{ tabindex: -1 }
+  .modal-dialog
+    #modal-peek-pg-queries-content.modal-content
+      .modal-header
+        %a.close{ href: "#", "data-dismiss" => "modal" } ×
+        %h4
+          SQL queries
+      .modal-body{ data: { defer_to: "#{view.defer_key}-queries" } }...
diff --git a/changelogs/unreleased/29010-perf-bar.yml b/changelogs/unreleased/29010-perf-bar.yml
new file mode 100644
index 00000000000..f4167e5562f
--- /dev/null
+++ b/changelogs/unreleased/29010-perf-bar.yml
@@ -0,0 +1,4 @@
+---
+title: Add an optional performance bar to view performance metrics for the current page
+merge_request: 11439
+author:
diff --git a/config/application.rb b/config/application.rb
index b0533759252..8bbecf3ed0f 100644
--- a/config/application.rb
+++ b/config/application.rb
@@ -105,6 +105,7 @@ module Gitlab
     config.assets.precompile << "katex.css"
     config.assets.precompile << "katex.js"
     config.assets.precompile << "xterm/xterm.css"
+    config.assets.precompile << "peek.css"
     config.assets.precompile << "lib/ace.js"
     config.assets.precompile << "vendor/assets/fonts/*"
     config.assets.precompile << "test.css"
diff --git a/config/initializers/peek.rb b/config/initializers/peek.rb
new file mode 100644
index 00000000000..65432caac2a
--- /dev/null
+++ b/config/initializers/peek.rb
@@ -0,0 +1,32 @@
+Rails.application.config.peek.adapter = :redis, { client: ::Redis.new(Gitlab::Redis.params) }
+
+Peek.into Peek::Views::Host
+Peek.into Peek::Views::PerformanceBar
+if Gitlab::Database.mysql?
+  require 'peek-mysql2'
+  PEEK_DB_CLIENT = ::Mysql2::Client
+  PEEK_DB_VIEW = Peek::Views::Mysql2
+else
+  require 'peek-pg'
+  PEEK_DB_CLIENT = ::PG::Connection
+  PEEK_DB_VIEW = Peek::Views::PG
+end
+Peek.into PEEK_DB_VIEW
+Peek.into Peek::Views::Redis
+Peek.into Peek::Views::Sidekiq
+Peek.into Peek::Views::Rblineprof
+Peek.into Peek::Views::GC
+
+# rubocop:disable Style/ClassAndModuleCamelCase
+class PEEK_DB_CLIENT
+  class << self
+    attr_accessor :query_details
+  end
+  self.query_details = Concurrent::Array.new
+end
+
+PEEK_DB_VIEW.prepend ::Gitlab::PerformanceBar::PeekQueryTracker
+
+class Peek::Views::PerformanceBar::ProcessUtilization
+  prepend ::Gitlab::PerformanceBar::PeekPerformanceBarWithRackBody
+end
diff --git a/config/routes.rb b/config/routes.rb
index d909be38b42..4fd6cb5d439 100644
--- a/config/routes.rb
+++ b/config/routes.rb
@@ -42,6 +42,7 @@ Rails.application.routes.draw do
     get 'liveness' => 'health#liveness'
     get 'readiness' => 'health#readiness'
     resources :metrics, only: [:index]
+    mount Peek::Railtie => '/peek'
   end
 
   # Koding route
diff --git a/config/webpack.config.js b/config/webpack.config.js
index c5060669da1..120f9d3193d 100644
--- a/config/webpack.config.js
+++ b/config/webpack.config.js
@@ -78,6 +78,7 @@ var config = {
     raven:                './raven/index.js',
     vue_merge_request_widget: './vue_merge_request_widget/index.js',
     test:                 './test.js',
+    peek:                 './peek.js',
   },
 
   output: {
diff --git a/doc/workflow/shortcuts.md b/doc/workflow/shortcuts.md
index c5b7488be69..87416008e98 100644
--- a/doc/workflow/shortcuts.md
+++ b/doc/workflow/shortcuts.md
@@ -6,7 +6,10 @@ You can see GitLab's keyboard shortcuts by using 'shift + ?'
 
 | Keyboard Shortcut | Description |
 | ----------------- | ----------- |
+| <kbd>n</kbd> | Main navigation |
 | <kbd>s</kbd> | Focus search |
+| <kbd>f</kbd> | Focus filter |
+| <kbd>p b</kbd> | Show/hide the Performance Bar |
 | <kbd>?</kbd> | Show/hide this dialog |
 | <kbd>⌘</kbd> + <kbd>shift</kbd> + <kbd>p</kbd> | Toggle markdown preview |
 | <kbd>↑</kbd> | Edit last comment (when focused on an empty textarea) |
diff --git a/lib/gitlab/performance_bar.rb b/lib/gitlab/performance_bar.rb
new file mode 100644
index 00000000000..163a40ad306
--- /dev/null
+++ b/lib/gitlab/performance_bar.rb
@@ -0,0 +1,7 @@
+module Gitlab
+  module PerformanceBar
+    def self.enabled?
+      Feature.enabled?('gitlab_performance_bar')
+    end
+  end
+end
diff --git a/lib/gitlab/performance_bar/peek_performance_bar_with_rack_body.rb b/lib/gitlab/performance_bar/peek_performance_bar_with_rack_body.rb
new file mode 100644
index 00000000000..d939a6ea18d
--- /dev/null
+++ b/lib/gitlab/performance_bar/peek_performance_bar_with_rack_body.rb
@@ -0,0 +1,22 @@
+# This solves a bug with a X-Senfile header that wouldn't be set properly, see
+# https://github.com/peek/peek-performance_bar/pull/27
+module Gitlab
+  module PerformanceBar
+    module PeekPerformanceBarWithRackBody
+      def call(env)
+        @env = env
+        reset_stats
+
+        @total_requests += 1
+        first_request if @total_requests == 1
+
+        env['process.request_start'] = @start.to_f
+        env['process.total_requests'] = total_requests
+
+        status, headers, body = @app.call(env)
+        body = Rack::BodyProxy.new(body) { record_request }
+        [status, headers, body]
+      end
+    end
+  end
+end
diff --git a/lib/gitlab/performance_bar/peek_query_tracker.rb b/lib/gitlab/performance_bar/peek_query_tracker.rb
new file mode 100644
index 00000000000..7ab80f5ee0f
--- /dev/null
+++ b/lib/gitlab/performance_bar/peek_query_tracker.rb
@@ -0,0 +1,39 @@
+# Inspired by https://github.com/peek/peek-pg/blob/master/lib/peek/views/pg.rb
+module Gitlab
+  module PerformanceBar
+    module PeekQueryTracker
+      def sorted_queries
+        PEEK_DB_CLIENT.query_details.
+          sort { |a, b| b[:duration] <=> a[:duration] }
+      end
+
+      def results
+        super.merge(queries: sorted_queries)
+      end
+
+      private
+
+      def setup_subscribers
+        super
+
+        # Reset each counter when a new request starts
+        before_request do
+          PEEK_DB_CLIENT.query_details = []
+        end
+
+        subscribe('sql.active_record') do |_, start, finish, _, data|
+          if RequestStore.active? && RequestStore.store[:peek_enabled]
+            track_query(data[:sql].strip, data[:binds], start, finish)
+          end
+        end
+      end
+
+      def track_query(raw_query, bindings, start, finish)
+        query = Gitlab::Sherlock::Query.new(raw_query, start, finish)
+        query_info = { duration: '%.3f' % query.duration, sql: query.formatted_query }
+
+        PEEK_DB_CLIENT.query_details << query_info
+      end
+    end
+  end
+end
diff --git a/lib/peek/rblineprof/custom_controller_helpers.rb b/lib/peek/rblineprof/custom_controller_helpers.rb
new file mode 100644
index 00000000000..99f9c2c9b04
--- /dev/null
+++ b/lib/peek/rblineprof/custom_controller_helpers.rb
@@ -0,0 +1,96 @@
+module Peek
+  module Rblineprof
+    module CustomControllerHelpers
+      extend ActiveSupport::Concern
+
+      # This will become useless once https://github.com/peek/peek-rblineprof/pull/5
+      # is merged
+      def pygmentize(file_name, code, lexer = nil)
+        if lexer.present?
+          Gitlab::Highlight.highlight(file_name, code)
+        else
+          "<pre>#{Rack::Utils.escape_html(code)}</pre>"
+        end
+      end
+
+      # rubocop:disable all
+      def inject_rblineprof
+        ret = nil
+        profile = lineprof(rblineprof_profiler_regex) do
+          ret = yield
+        end
+
+        if response.content_type =~ %r|text/html|
+          sort = params[:lineprofiler_sort]
+          mode = params[:lineprofiler_mode] || 'cpu'
+          min  = (params[:lineprofiler_min] || 5).to_i * 1000
+          summary = params[:lineprofiler_summary]
+
+          # Sort each file by the longest calculated time
+          per_file = profile.map do |file, lines|
+            total, child, excl, total_cpu, child_cpu, excl_cpu = lines[0]
+
+            wall = summary == 'exclusive' ? excl : total
+            cpu  = summary == 'exclusive' ? excl_cpu : total_cpu
+            idle = summary == 'exclusive' ? (excl - excl_cpu) : (total - total_cpu)
+
+            [
+              file, lines,
+              wall, cpu, idle,
+              sort == 'idle' ? idle : sort == 'cpu' ? cpu : wall
+            ]
+          end.sort_by{ |a,b,c,d,e,f| -f }
+
+          output = ''
+          per_file.each do |file_name, lines, file_wall, file_cpu, file_idle, file_sort|
+
+            output << "<div class='peek-rblineprof-file'><div class='heading'>"
+
+            show_src = file_sort > min
+            tmpl = show_src ? "<a href='#' class='js-lineprof-file'>%s</a>" : "%s"
+
+            if mode == 'cpu'
+              output << sprintf("<span class='duration'>% 8.1fms + % 8.1fms</span> #{tmpl}", file_cpu / 1000.0, file_idle / 1000.0, file_name.sub(Rails.root.to_s + '/', ''))
+            else
+              output << sprintf("<span class='duration'>% 8.1fms</span> #{tmpl}", file_wall/1000.0, file_name.sub(Rails.root.to_s + '/', ''))
+            end
+
+            output << "</div>" # .heading
+
+            next unless show_src
+
+            output << "<div class='data'>"
+            code = []
+            times = []
+            File.readlines(file_name).each_with_index do |line, i|
+              code << line
+              wall, cpu, calls = lines[i + 1]
+
+              if calls && calls > 0
+                if mode == 'cpu'
+                  idle = wall - cpu
+                  times << sprintf("% 8.1fms + % 8.1fms (% 5d)", cpu / 1000.0, idle / 1000.0, calls)
+                else
+                  times << sprintf("% 8.1fms (% 5d)", wall / 1000.0, calls)
+                end
+              else
+                times << ' '
+              end
+            end
+            output << "<pre class='duration'>#{times.join("\n")}</pre>"
+            # The following line was changed from
+            # https://github.com/peek/peek-rblineprof/blob/8d3b7a283a27de2f40abda45974516693d882258/lib/peek/rblineprof/controller_helpers.rb#L125
+            # This will become useless once https://github.com/peek/peek-rblineprof/pull/16
+            # is merged and is implemented.
+            output << "<pre class='code highlight white'>#{pygmentize(file_name, code.join, 'ruby')}</pre>"
+            output << "</div></div>" # .data then .peek-rblineprof-file
+          end
+
+          response.body += "<div class='peek-rblineprof-modal' id='line-profile'>#{output}</div>".html_safe
+        end
+
+        ret
+      end
+    end
+  end
+end
diff --git a/spec/features/user_can_display_performance_bar_spec.rb b/spec/features/user_can_display_performance_bar_spec.rb
new file mode 100644
index 00000000000..c2842255b86
--- /dev/null
+++ b/spec/features/user_can_display_performance_bar_spec.rb
@@ -0,0 +1,81 @@
+require 'rails_helper'
+
+describe 'User can display performacne bar', :js do
+  shared_examples 'performance bar is disabled' do
+    it 'does not show the performance bar by default' do
+      expect(page).not_to have_css('#peek')
+    end
+
+    context 'when user press `pb`' do
+      before do
+        find('body').native.send_keys('pb')
+      end
+
+      it 'does not show the performance bar by default' do
+        expect(page).not_to have_css('#peek')
+      end
+    end
+  end
+
+  shared_examples 'performance bar is enabled' do
+    it 'does not show the performance bar by default' do
+      expect(page).not_to have_css('#peek')
+    end
+
+    context 'when user press `pb`' do
+      before do
+        find('body').native.send_keys('pb')
+      end
+
+      it 'does not show the performance bar by default' do
+        expect(page).not_to have_css('#peek')
+      end
+    end
+  end
+
+  context 'when user is logged-out' do
+    before do
+      visit root_path
+    end
+
+    context 'when the gitlab_performance_bar feature is disabled' do
+      before do
+        Feature.disable('gitlab_performance_bar')
+      end
+
+      it_behaves_like 'performance bar is disabled'
+    end
+
+    context 'when the gitlab_performance_bar feature is enabled' do
+      before do
+        Feature.enable('gitlab_performance_bar')
+      end
+
+      it_behaves_like 'performance bar is disabled'
+    end
+  end
+
+  context 'when user is logged-in' do
+    before do
+      login_as :user
+
+      visit root_path
+    end
+
+    context 'when the gitlab_performance_bar feature is disabled' do
+      before do
+        Feature.disable('gitlab_performance_bar')
+      end
+
+      it_behaves_like 'performance bar is disabled'
+    end
+
+    context 'when the gitlab_performance_bar feature is enabled' do
+      before do
+        Feature.enable('gitlab_performance_bar')
+      end
+
+      it_behaves_like 'performance bar is enabled'
+    end
+  end
+end
diff --git a/spec/models/commit_spec.rb b/spec/models/commit_spec.rb
index 140fd2720bf..ba247dcc5cf 100644
--- a/spec/models/commit_spec.rb
+++ b/spec/models/commit_spec.rb
@@ -20,8 +20,8 @@ describe Commit, models: true do
     end
 
     it 'caches the author' do
+      allow(RequestStore).to receive(:active?).and_return(true)
       user = create(:user, email: commit.author_email)
-      expect(RequestStore).to receive(:active?).twice.and_return(true)
       expect_any_instance_of(Commit).to receive(:find_author_by_any_email).and_call_original
 
       expect(commit.author).to eq(user)
diff --git a/vendor/assets/javascripts/peek.js b/vendor/assets/javascripts/peek.js
new file mode 100644
index 00000000000..f7e77de34ff
--- /dev/null
+++ b/vendor/assets/javascripts/peek.js
@@ -0,0 +1,78 @@
+(function($) {
+  var fetchRequestResults, getRequestId, peekEnabled, toggleBar, updatePerformanceBar;
+  getRequestId = function() {
+    return $('#peek').data('request-id');
+  };
+  peekEnabled = function() {
+    return $('#peek').length;
+  };
+  updatePerformanceBar = function(results) {
+    var key, label, data, table, html, tr, duration_td, sql_td, strong;
+
+    Object.keys(results.data).forEach(function(key) {
+      Object.keys(results.data[key]).forEach(function(label) {
+        data = results.data[key][label];
+
+        if (label == 'queries') {
+          table = document.createElement('table');
+
+          for (var i = 0; i < data.length; i += 1) {
+            tr = document.createElement('tr');
+            duration_td = document.createElement('td');
+            sql_td = document.createElement('td');
+            strong = document.createElement('strong');
+
+            strong.append(data[i]['duration'] + 'ms');
+            duration_td.appendChild(strong);
+            tr.appendChild(duration_td);
+
+            sql_td.appendChild(document.createTextNode(data[i]['sql']));
+            tr.appendChild(sql_td);
+
+            table.appendChild(tr);
+          }
+
+          table.className = 'table';
+          $("[data-defer-to=" + key + "-" + label + "]").html(table);
+        } else {
+          $("[data-defer-to=" + key + "-" + label + "]").text(results.data[key][label]);
+        }
+      });
+    });
+    return $(document).trigger('peek:render', [getRequestId(), results]);
+  };
+  toggleBar = function(event) {
+    var wrapper;
+    if ($(event.target).is(':input')) {
+      return;
+    }
+    if (event.which === 96 && !event.metaKey) {
+      wrapper = $('#peek');
+      if (wrapper.hasClass('disabled')) {
+        wrapper.removeClass('disabled');
+        return document.cookie = "peek=true; path=/";
+      } else {
+        wrapper.addClass('disabled');
+        return document.cookie = "peek=false; path=/";
+      }
+    }
+  };
+  fetchRequestResults = function() {
+    return $.ajax('/-/peek/results', {
+      data: {
+        request_id: getRequestId()
+      },
+      success: function(data, textStatus, xhr) {
+        return updatePerformanceBar(data);
+      },
+      error: function(xhr, textStatus, error) {}
+    });
+  };
+  $(document).on('keypress', toggleBar);
+  $(document).on('peek:update', fetchRequestResults);
+  return $(function() {
+    if (peekEnabled()) {
+      return $(this).trigger('peek:update');
+    }
+  });
+})(jQuery);
diff --git a/vendor/assets/javascripts/peek.performance_bar.js b/vendor/assets/javascripts/peek.performance_bar.js
new file mode 100644
index 00000000000..6ed86dce2f2
--- /dev/null
+++ b/vendor/assets/javascripts/peek.performance_bar.js
@@ -0,0 +1,182 @@
+var PerformanceBar, ajaxStart, renderPerformanceBar, updateStatus;
+
+PerformanceBar = (function() {
+  PerformanceBar.prototype.appInfo = null;
+
+  PerformanceBar.prototype.width = null;
+
+  PerformanceBar.formatTime = function(value) {
+    if (value >= 1000) {
+      return ((value / 1000).toFixed(3)) + "s";
+    } else {
+      return (value.toFixed(0)) + "ms";
+    }
+  };
+
+  function PerformanceBar(options) {
+    var k, v;
+    if (options == null) {
+      options = {};
+    }
+    this.el = $('#peek-view-performance-bar .performance-bar');
+    for (k in options) {
+      v = options[k];
+      this[k] = v;
+    }
+    if (this.width == null) {
+      this.width = this.el.width();
+    }
+    if (this.timing == null) {
+      this.timing = window.performance.timing;
+    }
+  }
+
+  PerformanceBar.prototype.render = function(serverTime) {
+    var networkTime, perfNetworkTime;
+    if (serverTime == null) {
+      serverTime = 0;
+    }
+    this.el.empty();
+    this.addBar('frontend', '#90d35b', 'domLoading', 'domInteractive');
+    perfNetworkTime = this.timing.responseEnd - this.timing.requestStart;
+    if (serverTime && serverTime <= perfNetworkTime) {
+      networkTime = perfNetworkTime - serverTime;
+      this.addBar('latency / receiving', '#f1faff', this.timing.requestStart + serverTime, this.timing.requestStart + serverTime + networkTime);
+      this.addBar('app', '#90afcf', this.timing.requestStart, this.timing.requestStart + serverTime, this.appInfo);
+    } else {
+      this.addBar('backend', '#c1d7ee', 'requestStart', 'responseEnd');
+    }
+    this.addBar('tcp / ssl', '#45688e', 'connectStart', 'connectEnd');
+    this.addBar('redirect', '#0c365e', 'redirectStart', 'redirectEnd');
+    this.addBar('dns', '#082541', 'domainLookupStart', 'domainLookupEnd');
+    return this.el;
+  };
+
+  PerformanceBar.prototype.isLoaded = function() {
+    return this.timing.domInteractive;
+  };
+
+  PerformanceBar.prototype.start = function() {
+    return this.timing.navigationStart;
+  };
+
+  PerformanceBar.prototype.end = function() {
+    return this.timing.domInteractive;
+  };
+
+  PerformanceBar.prototype.total = function() {
+    return this.end() - this.start();
+  };
+
+  PerformanceBar.prototype.addBar = function(name, color, start, end, info) {
+    var bar, left, offset, time, title, width;
+    if (typeof start === 'string') {
+      start = this.timing[start];
+    }
+    if (typeof end === 'string') {
+      end = this.timing[end];
+    }
+    if (!((start != null) && (end != null))) {
+      return;
+    }
+    time = end - start;
+    offset = start - this.start();
+    left = this.mapH(offset);
+    width = this.mapH(time);
+    title = name + ": " + (PerformanceBar.formatTime(time));
+    bar = $('<li></li>', {
+      'data-title': title,
+      'data-toggle': 'tooltip',
+      'data-container': 'body'
+    });
+    bar.css({
+      width: width + "px",
+      left: left + "px",
+      background: color
+    });
+    return this.el.append(bar);
+  };
+
+  PerformanceBar.prototype.mapH = function(offset) {
+    return offset * (this.width / this.total());
+  };
+
+  return PerformanceBar;
+
+})();
+
+renderPerformanceBar = function() {
+  var bar, resp, span, time;
+  resp = $('#peek-server_response_time');
+  time = Math.round(resp.data('time') * 1000);
+  bar = new PerformanceBar;
+  bar.render(time);
+  span = $('<span>', {
+    'data-toggle': 'tooltip',
+    'data-title': 'Total navigation time for this page.',
+    'data-container': 'body'
+  }).text(PerformanceBar.formatTime(bar.total()));
+  return updateStatus(span);
+};
+
+updateStatus = function(html) {
+  return $('#serverstats').html(html);
+};
+
+ajaxStart = null;
+
+$(document).on('pjax:start page:fetch turbolinks:request-start', function(event) {
+  return ajaxStart = event.timeStamp;
+});
+
+$(document).on('pjax:end page:load turbolinks:load', function(event, xhr) {
+  var ajaxEnd, serverTime, total;
+  if (ajaxStart == null) {
+    return;
+  }
+  ajaxEnd = event.timeStamp;
+  total = ajaxEnd - ajaxStart;
+  serverTime = xhr ? parseInt(xhr.getResponseHeader('X-Runtime')) : 0;
+  return setTimeout(function() {
+    var bar, now, span, tech;
+    now = new Date().getTime();
+    bar = new PerformanceBar({
+      timing: {
+        requestStart: ajaxStart,
+        responseEnd: ajaxEnd,
+        domLoading: ajaxEnd,
+        domInteractive: now
+      },
+      isLoaded: function() {
+        return true;
+      },
+      start: function() {
+        return ajaxStart;
+      },
+      end: function() {
+        return now;
+      }
+    });
+    bar.render(serverTime);
+    if ($.fn.pjax != null) {
+      tech = 'PJAX';
+    } else {
+      tech = 'Turbolinks';
+    }
+    span = $('<span>', {
+      'data-toggle': 'tooltip',
+      'data-title': tech + " navigation time",
+      'data-container': 'body'
+    }).text(PerformanceBar.formatTime(total));
+    updateStatus(span);
+    return ajaxStart = null;
+  }, 0);
+});
+
+$(function() {
+  if (window.performance) {
+    return renderPerformanceBar();
+  } else {
+    return $('#peek-view-performance-bar').remove();
+  }
+});
diff --git a/vendor/assets/stylesheets/peek.scss b/vendor/assets/stylesheets/peek.scss
new file mode 100644
index 00000000000..f1845fb9044
--- /dev/null
+++ b/vendor/assets/stylesheets/peek.scss
@@ -0,0 +1,94 @@
+//= require peek/views/performance_bar
+//= require peek/views/rblineprof
+
+header.navbar-gitlab.with-peek {
+  top: 35px;
+}
+
+#peek {
+  height: 35px;
+  background: #000;
+  line-height: 35px;
+  color: #999;
+
+  &.disabled {
+    display: none;
+  }
+
+  &.production {
+    background-color: #222;
+  }
+
+  &.staging {
+    background-color: #291430;
+  }
+
+  &.development {
+    background-color: #4c1210;
+  }
+
+  .wrapper {
+    width: 800px;
+    margin: 0 auto;
+  }
+
+  // UI Elements
+  .bucket {
+    background: #111;
+    display: inline-block;
+    padding: 4px 6px;
+    font-family: Consolas, "Liberation Mono", Courier, monospace;
+    line-height: 1;
+    color: #ccc;
+    border-radius: 3px;
+    box-shadow: 0 1px 0 rgba(255,255,255,.2), inset 0 1px 2px rgba(0,0,0,.25);
+
+    .hidden {
+      display: none;
+    }
+
+    &:hover .hidden {
+      display: inline;
+    }
+  }
+
+  strong {
+    color: #fff;
+  }
+
+  table {
+    strong {
+      color: #000;
+    }
+  }
+
+  .view {
+    margin-right: 15px;
+    float: left;
+
+    &:last-child {
+      margin-right: 0;
+    }
+  }
+
+  .css-truncate {
+    &.css-truncate-target,
+    .css-truncate-target {
+      display: inline-block;
+      max-width: 125px;
+      overflow: hidden;
+      text-overflow: ellipsis;
+      white-space: nowrap;
+      vertical-align: top;
+    }
+
+    &.expandable:hover .css-truncate-target,
+    &.expandable:hover.css-truncate-target {
+      max-width: 10000px !important;
+    }
+  }
+}
+
+#modal-peek-pg-queries-content {
+  color: #000;
+}