Add latest changes from gitlab-org/gitlab@master

75 files changed, 1096 insertions, 809 deletions

diff --git a/.rubocop_todo/gitlab/json.yml b/.rubocop_todo/gitlab/json.yml
index 727ccda4983..78c54dc157d 100644
--- a/.rubocop_todo/gitlab/json.yml
+++ b/.rubocop_todo/gitlab/json.yml
@@ -19,32 +19,10 @@ Gitlab/Json:
     - 'app/controllers/projects_controller.rb'
     - 'app/controllers/search_controller.rb'
     - 'app/mailers/emails/members.rb'
-    - 'app/models/concerns/redis_cacheable.rb'
-    - 'app/models/diff_discussion.rb'
-    - 'app/models/integrations/assembla.rb'
-    - 'app/models/integrations/pivotaltracker.rb'
-    - 'app/models/integrations/pumble.rb'
-    - 'app/models/integrations/unify_circuit.rb'
-    - 'app/models/integrations/webex_teams.rb'
-    - 'app/models/merge_request_diff_commit.rb'
     - 'app/presenters/packages/composer/packages_presenter.rb'
     - 'app/presenters/projects/security/configuration_presenter.rb'
     - 'app/workers/google_cloud/create_cloudsql_instance_worker.rb'
     - 'config/initializers/rack_multipart_patch.rb'
-    - 'db/migrate/20210305031822_create_dast_site_profile_variables.rb'
-    - 'db/migrate/20210317035357_create_dast_profiles_pipelines.rb'
-    - 'db/migrate/20210412111213_create_security_orchestration_policy_rule_schedule.rb'
-    - 'db/migrate/20210423054022_create_dast_site_profiles_pipelines.rb'
-    - 'db/migrate/20210604032738_create_dast_site_profiles_builds.rb'
-    - 'db/migrate/20210604051330_create_dast_scanner_profiles_builds.rb'
-    - 'db/migrate/20210713123345_create_dast_profile_schedule.rb'
-    - 'db/post_migrate/20210311120155_backfill_events_id_for_bigint_conversion.rb'
-    - 'db/post_migrate/20210311120156_backfill_push_event_payload_event_id_for_bigint_conversion.rb'
-    - 'db/post_migrate/20210415101228_backfill_ci_build_needs_for_bigint_conversion.rb'
-    - 'db/post_migrate/20210420121149_backfill_conversion_of_ci_job_artifacts.rb'
-    - 'db/post_migrate/20210422023046_backfill_ci_sources_pipelines_source_job_id_for_bigint_conversion.rb'
-    - 'db/post_migrate/20210615234935_fix_batched_migrations_old_format_job_arguments.rb'
-    - 'db/post_migrate/20221006172302_adjust_task_note_rename_background_migration_values.rb'
     - 'ee/app/controllers/admin/geo/nodes_controller.rb'
     - 'ee/app/controllers/ee/admin/application_settings_controller.rb'
     - 'ee/app/controllers/ee/search_controller.rb'
diff --git a/Gemfile b/Gemfile
index 0a96ff0c8ec..41ba90e945e 100644
--- a/Gemfile
+++ b/Gemfile
@@ -130,8 +130,6 @@ gem 'graphql-docs', '~> 2.1.0', group: [:development, :test]
 gem 'graphlient', '~> 0.5.0' # Used by BulkImport feature (group::import)
 
 gem 'hashie', '~> 5.0.0'
-# Disable strong_params so that Mash does not respond to :permitted?
-gem 'hashie-forbidden_attributes'
 
 # Pagination
 gem 'kaminari', '~> 1.2.2'
@@ -193,7 +191,7 @@ gem 'asciidoctor-kroki', '~> 0.5.0', require: false
 gem 'rouge', '~> 3.30.0'
 gem 'truncato', '~> 0.7.12'
 gem 'bootstrap_form', '~> 4.2.0'
-gem 'nokogiri', '~> 1.13.8'
+gem 'nokogiri', '~> 1.13.9'
 
 # Calendar rendering
 gem 'icalendar'
diff --git a/Gemfile.checksum b/Gemfile.checksum
index a9d2e4d59bc..4515a62d10e 100644
--- a/Gemfile.checksum
+++ b/Gemfile.checksum
@@ -260,7 +260,6 @@
 {"name":"hangouts-chat","version":"0.0.5","platform":"ruby","checksum":"bdbeb6c6e4abc98f395cb273f53b39911b3aa9e248fbbf063242b021ced8b6b6"},
 {"name":"hashdiff","version":"1.0.1","platform":"ruby","checksum":"2cd4d04f5080314ecc8403c4e2e00dbaa282dff395e2d031bc16c8d501bdd6db"},
 {"name":"hashie","version":"5.0.0","platform":"ruby","checksum":"9d6c4e51f2a36d4616cbc8a322d619a162d8f42815a792596039fc95595603da"},
-{"name":"hashie-forbidden_attributes","version":"0.1.1","platform":"ruby","checksum":"3a6ed37f3a314e4fb1dd1e2df6eb7721bcadd023a30bc0b951b2b5285a790fb2"},
 {"name":"health_check","version":"3.1.0","platform":"ruby","checksum":"10146508237dc54ed7e24c292d8ba7fb8f9590cf26c66e325b947438c4103b57"},
 {"name":"heapy","version":"0.2.0","platform":"ruby","checksum":"74141e845d61ffc7c1e8bf8b127c8cf94544ec7a1181aec613288682543585ea"},
 {"name":"html-pipeline","version":"2.14.3","platform":"ruby","checksum":"8a1d4d7128b2141913387cac0f8ba898bb6812557001acc0c2b46910f59413a0"},
@@ -358,16 +357,16 @@
 {"name":"nio4r","version":"2.5.8","platform":"java","checksum":"b2b1800f6bf7ce4b797ca8b639ad278a99c9c904fb087a91d944f38e4bd71401"},
 {"name":"nio4r","version":"2.5.8","platform":"ruby","checksum":"3becb4ad95ab8ac0a9bd2e1b16466869402be62848082bf6329ae9091f276676"},
 {"name":"no_proxy_fix","version":"0.1.2","platform":"ruby","checksum":"4e9b4c31bb146de7fcf347dc1087bb13ac2039b56d50aa019e61036256abcd00"},
-{"name":"nokogiri","version":"1.13.8","platform":"aarch64-linux","checksum":"d6b2c45a57738f12fe27783939fe1394e7049246288c7770d3b1fee7f49432a6"},
-{"name":"nokogiri","version":"1.13.8","platform":"arm64-darwin","checksum":"00217e48a6995e81dd83014325c0ea0b015023a8922c7bdb2ef1416aa87c1f43"},
-{"name":"nokogiri","version":"1.13.8","platform":"java","checksum":"9d04c616900e2b5118e501436ebb9bc48520d08f3695d012a314006e28082f72"},
-{"name":"nokogiri","version":"1.13.8","platform":"ruby","checksum":"79c279298b2f22fd4e760f49990c7930436bac1b1cfeff7bacff192f30edea3c"},
-{"name":"nokogiri","version":"1.13.8","platform":"x64-mingw-ucrt","checksum":"98f7dac7583f07a84ec3fcc01dc03a66fce10f412cd363fce7de749acdb2a42d"},
-{"name":"nokogiri","version":"1.13.8","platform":"x64-mingw32","checksum":"117a71b37f2e1d774a9f031d393e72d5d04b92af8036e0c1a8dd509c247b2013"},
-{"name":"nokogiri","version":"1.13.8","platform":"x86-linux","checksum":"6d04342456edfb8fbc041d0c2cf5a59baaa7aacdda414b2333100b02f85d441d"},
-{"name":"nokogiri","version":"1.13.8","platform":"x86-mingw32","checksum":"0529d558b4280a55bc7af500d3d4d590b7c059c814a0cea52e4e18cb30c25d15"},
-{"name":"nokogiri","version":"1.13.8","platform":"x86_64-darwin","checksum":"8966d79e687b271df87a4b240456597c43cd98584e3f783fc35de4f066486421"},
-{"name":"nokogiri","version":"1.13.8","platform":"x86_64-linux","checksum":"344f1bc66feac787e5b2053c6e9095d1f33605083e58ddf2b8d4eef257bccc5f"},
+{"name":"nokogiri","version":"1.13.9","platform":"aarch64-linux","checksum":"9b69829561d30c4461ea803baeaf3460e8b145cff7a26ce397119577a4083a02"},
+{"name":"nokogiri","version":"1.13.9","platform":"arm64-darwin","checksum":"e76ebb4b7b2e02c72b2d1541289f8b0679fb5984867cf199d89b8ef485764956"},
+{"name":"nokogiri","version":"1.13.9","platform":"java","checksum":"15bae7d08bddeaa898d8e3f558723300137c26a2dc2632a1f89c8574c4467165"},
+{"name":"nokogiri","version":"1.13.9","platform":"ruby","checksum":"96f37c1baf0234d3ae54c2c89aef7220d4a8a1b03d2675ff7723565b0a095531"},
+{"name":"nokogiri","version":"1.13.9","platform":"x64-mingw-ucrt","checksum":"f6a1dbc7229184357f3129503530af73cc59ceba4932c700a458a561edbe04b9"},
+{"name":"nokogiri","version":"1.13.9","platform":"x64-mingw32","checksum":"36d935d799baa4dc488024f71881ff0bc8b172cecdfc54781169c40ec02cbdb3"},
+{"name":"nokogiri","version":"1.13.9","platform":"x86-linux","checksum":"ebaf82aa9a11b8fafb67873d19ee48efb565040f04c898cdce8ca0cd53ff1a12"},
+{"name":"nokogiri","version":"1.13.9","platform":"x86-mingw32","checksum":"11789a2a11b28bc028ee111f23311461104d8c4468d5b901ab7536b282504154"},
+{"name":"nokogiri","version":"1.13.9","platform":"x86_64-darwin","checksum":"01830e1646803ff91c0fe94bc768ff40082c6de8cfa563dafd01b3f7d5f9d795"},
+{"name":"nokogiri","version":"1.13.9","platform":"x86_64-linux","checksum":"8e93b8adec22958013799c8690d81c2cdf8a90b6f6e8150ab22e11895844d781"},
 {"name":"notiffany","version":"0.1.3","platform":"ruby","checksum":"d37669605b7f8dcb04e004e6373e2a780b98c776f8eb503ac9578557d7808738"},
 {"name":"numerizer","version":"0.2.0","platform":"ruby","checksum":"e58076d5ee5370417b7e52d9cb25836d62acd1b8d9a194c308707986c1705d7b"},
 {"name":"oauth","version":"0.5.6","platform":"ruby","checksum":"4085fe28e0c5e2434135e00a6555294fd2a4ff96a98d1bdecdcd619fc6368dff"},
diff --git a/Gemfile.lock b/Gemfile.lock
index cd1da4b7c76..05252a7a2f8 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -710,8 +710,6 @@ GEM
     hangouts-chat (0.0.5)
     hashdiff (1.0.1)
     hashie (5.0.0)
-    hashie-forbidden_attributes (0.1.1)
-      hashie (>= 3.0)
     health_check (3.1.0)
       railties (>= 5.0)
     heapy (0.2.0)
@@ -908,7 +906,7 @@ GEM
     netrc (0.11.0)
     nio4r (2.5.8)
     no_proxy_fix (0.1.2)
-    nokogiri (1.13.8)
+    nokogiri (1.13.9)
       mini_portile2 (~> 2.8.0)
       racc (~> 1.4)
     notiffany (0.1.3)
@@ -1665,7 +1663,6 @@ DEPENDENCIES
   hamlit (~> 2.15.0)
   hangouts-chat (~> 0.0.5)
   hashie (~> 5.0.0)
-  hashie-forbidden_attributes
   health_check (~> 3.0)
   html-pipeline (~> 2.14.3)
   html2text
@@ -1704,7 +1701,7 @@ DEPENDENCIES
   multi_json (~> 1.14.1)
   net-ldap (~> 0.16.3)
   net-ntp
-  nokogiri (~> 1.13.8)
+  nokogiri (~> 1.13.9)
   oauth2 (~> 2.0)
   octokit (~> 4.15)
   ohai (~> 16.10)
diff --git a/app/assets/javascripts/behaviors/markdown/render_gfm.js b/app/assets/javascripts/behaviors/markdown/render_gfm.js
index ee5c0fe5ef3..a08cf48c327 100644
--- a/app/assets/javascripts/behaviors/markdown/render_gfm.js
+++ b/app/assets/javascripts/behaviors/markdown/render_gfm.js
@@ -15,7 +15,7 @@ $.fn.renderGFM = function renderGFM() {
   syntaxHighlight(this.find('.js-syntax-highlight').get());
   renderKroki(this.find('.js-render-kroki[hidden]').get());
   renderMath(this.find('.js-render-math'));
-  renderSandboxedMermaid(this.find('.js-render-mermaid'));
+  renderSandboxedMermaid(this.find('.js-render-mermaid').get());
   renderJSONTable(
     Array.from(this.find('[lang="json"][data-lang-params="table"]').get()).map((e) => e.parentNode),
   );
diff --git a/app/assets/javascripts/behaviors/markdown/render_sandboxed_mermaid.js b/app/assets/javascripts/behaviors/markdown/render_sandboxed_mermaid.js
index 077e96b2fee..031b03e0d59 100644
--- a/app/assets/javascripts/behaviors/markdown/render_sandboxed_mermaid.js
+++ b/app/assets/javascripts/behaviors/markdown/render_sandboxed_mermaid.js
@@ -1,5 +1,4 @@
-import $ from 'jquery';
-import { once, countBy } from 'lodash';
+import { countBy } from 'lodash';
 import { __ } from '~/locale';
 import {
   getBaseURL,
@@ -8,7 +7,8 @@ import {
   joinPaths,
 } from '~/lib/utils/url_utility';
 import { darkModeEnabled } from '~/lib/utils/color_utils';
-import { setAttributes } from '~/lib/utils/dom_utils';
+import { setAttributes, isElementVisible } from '~/lib/utils/dom_utils';
+import { createAlert, VARIANT_WARNING } from '~/flash';
 import { unrestrictedPages } from './constants';
 
 // Renders diagrams and flowcharts from text using Mermaid in any element with the
@@ -27,17 +27,30 @@ import { unrestrictedPages } from './constants';
 
 const SANDBOX_FRAME_PATH = '/-/sandbox/mermaid';
 // This is an arbitrary number; Can be iterated upon when suitable.
-const MAX_CHAR_LIMIT = 2000;
+export const MAX_CHAR_LIMIT = 2000;
 // Max # of mermaid blocks that can be rendered in a page.
-const MAX_MERMAID_BLOCK_LIMIT = 50;
+export const MAX_MERMAID_BLOCK_LIMIT = 50;
 // Max # of `&` allowed in Chaining of links syntax
 const MAX_CHAINING_OF_LINKS_LIMIT = 30;
+
 export const BUFFER_IFRAME_HEIGHT = 10;
 export const SANDBOX_ATTRIBUTES = 'allow-scripts allow-popups';
+
+const ALERT_CONTAINER_CLASS = 'mermaid-alert-container';
+export const LAZY_ALERT_SHOWN_CLASS = 'lazy-alert-shown';
+
 // Keep a map of mermaid blocks we've already rendered.
 const elsProcessingMap = new WeakMap();
 let renderedMermaidBlocks = 0;
 
+/**
+ * Determines whether a given Mermaid diagram is visible.
+ *
+ * @param {Element} el The Mermaid DOM node
+ * @returns
+ */
+const isVisibleMermaid = (el) => el.closest('details') === null && isElementVisible(el);
+
 function shouldLazyLoadMermaidBlock(source) {
   /**
    * If source contains `&`, which means that it might
@@ -104,8 +117,8 @@ function renderMermaidEl(el, source) {
   );
 }
 
-function renderMermaids($els) {
-  if (!$els.length) return;
+function renderMermaids(els) {
+  if (!els.length) return;
 
   const pageName = document.querySelector('body').dataset.page;
 
@@ -114,7 +127,7 @@ function renderMermaids($els) {
 
   let renderedChars = 0;
 
-  $els.each((i, el) => {
+  els.forEach((el) => {
     // Skipping all the elements which we've already queued in requestIdleCallback
     if (elsProcessingMap.has(el)) {
       return;
@@ -133,33 +146,29 @@ function renderMermaids($els) {
         renderedMermaidBlocks >= MAX_MERMAID_BLOCK_LIMIT ||
         shouldLazyLoadMermaidBlock(source))
     ) {
-      const html = `
-          <div class="alert gl-alert gl-alert-warning alert-dismissible lazy-render-mermaid-container js-lazy-render-mermaid-container fade show" role="alert">
-            <div>
-              <div>
-                <div class="js-warning-text"></div>
-                <div class="gl-alert-actions">
-                  <button type="button" class="js-lazy-render-mermaid btn gl-alert-action btn-confirm btn-md gl-button">Display</button>
-                </div>
-              </div>
-              <button type="button" class="close" data-dismiss="alert" aria-label="Close">
-                <span aria-hidden="true">&times;</span>
-              </button>
-            </div>
-          </div>
-          `;
-
-      const $parent = $(el).parent();
-
-      if (!$parent.hasClass('lazy-alert-shown')) {
-        $parent.after(html);
-        $parent
-          .siblings()
-          .find('.js-warning-text')
-          .text(
-            __('Warning: Displaying this diagram might cause performance issues on this page.'),
-          );
-        $parent.addClass('lazy-alert-shown');
+      const parent = el.parentNode;
+
+      if (!parent.classList.contains(LAZY_ALERT_SHOWN_CLASS)) {
+        const alertContainer = document.createElement('div');
+        alertContainer.classList.add(ALERT_CONTAINER_CLASS);
+        alertContainer.classList.add('gl-mb-5');
+        parent.after(alertContainer);
+        createAlert({
+          message: __(
+            'Warning: Displaying this diagram might cause performance issues on this page.',
+          ),
+          variant: VARIANT_WARNING,
+          parent: parent.parentNode,
+          containerSelector: `.${ALERT_CONTAINER_CLASS}`,
+          primaryButton: {
+            text: __('Display'),
+            clickHandler: () => {
+              alertContainer.remove();
+              renderMermaidEl(el, source);
+            },
+          },
+        });
+        parent.classList.add(LAZY_ALERT_SHOWN_CLASS);
       }
 
       return;
@@ -176,37 +185,33 @@ function renderMermaids($els) {
   });
 }
 
-const hookLazyRenderMermaidEvent = once(() => {
-  $(document.body).on('click', '.js-lazy-render-mermaid', function eventHandler() {
-    const parent = $(this).closest('.js-lazy-render-mermaid-container');
-    const pre = parent.prev();
-
-    const el = pre.find('.js-render-mermaid');
-
-    parent.remove();
-
-    // sandbox update
-    const element = el.get(0);
-    const { source } = fixElementSource(element);
+export default function renderMermaid(els) {
+  if (!els.length) return;
 
-    renderMermaidEl(element, source);
-  });
-});
-
-export default function renderMermaid($els) {
-  if (!$els.length) return;
+  const visibleMermaids = [];
+  const hiddenMermaids = [];
 
-  const visibleMermaids = $els.filter(function filter() {
-    return $(this).closest('details').length === 0 && $(this).is(':visible');
-  });
+  for (const el of els) {
+    if (isVisibleMermaid(el)) {
+      visibleMermaids.push(el);
+    } else {
+      hiddenMermaids.push(el);
+    }
+  }
 
   renderMermaids(visibleMermaids);
 
-  $els.closest('details').one('toggle', function toggle() {
-    if (this.open) {
-      renderMermaids($(this).find('.js-render-mermaid'));
-    }
+  hiddenMermaids.forEach((el) => {
+    el.closest('details').addEventListener(
+      'toggle',
+      ({ target: details }) => {
+        if (details.open) {
+          renderMermaids([...details.querySelectorAll('.js-render-mermaid')]);
+        }
+      },
+      {
+        once: true,
+      },
+    );
   });
-
-  hookLazyRenderMermaidEvent();
 }
diff --git a/app/assets/javascripts/issues/list/components/issues_list_app.vue b/app/assets/javascripts/issues/list/components/issues_list_app.vue
index a110ba658f7..09097e2d5ab 100644
--- a/app/assets/javascripts/issues/list/components/issues_list_app.vue
+++ b/app/assets/javascripts/issues/list/components/issues_list_app.vue
@@ -42,8 +42,6 @@ import {
 } from '~/vue_shared/components/filtered_search_bar/constants';
 import IssuableList from '~/vue_shared/issuable/list/components/issuable_list_root.vue';
 import { IssuableListTabs, IssuableStates } from '~/vue_shared/issuable/list/constants';
-import glFeatureFlagMixin from '~/vue_shared/mixins/gl_feature_flags_mixin';
-import { WORK_ITEM_TYPE_ENUM_TASK } from '~/work_items/constants';
 import {
   CREATED_DESC,
   defaultTypeTokenOptions,
@@ -125,7 +123,6 @@ export default {
   directives: {
     GlTooltip: GlTooltipDirective,
   },
-  mixins: [glFeatureFlagMixin()],
   inject: [
     'autocompleteAwardEmojisPath',
     'calendarPath',
@@ -239,21 +236,14 @@ export default {
         state: this.state,
         ...this.pageParams,
         ...this.apiFilterParams,
-        types: this.apiFilterParams.types || this.defaultWorkItemTypes,
+        types: this.apiFilterParams.types || defaultWorkItemTypes,
       };
     },
     namespace() {
       return this.isProject ? ITEM_TYPE.PROJECT : ITEM_TYPE.GROUP;
     },
-    defaultWorkItemTypes() {
-      return this.isWorkItemsEnabled
-        ? defaultWorkItemTypes
-        : defaultWorkItemTypes.filter((type) => type !== WORK_ITEM_TYPE_ENUM_TASK);
-    },
     typeTokenOptions() {
-      return this.isWorkItemsEnabled
-        ? defaultTypeTokenOptions.concat(TYPE_TOKEN_TASK_OPTION)
-        : defaultTypeTokenOptions;
+      return defaultTypeTokenOptions.concat(TYPE_TOKEN_TASK_OPTION);
     },
     hasSearch() {
       return (
@@ -272,9 +262,6 @@ export default {
     isOpenTab() {
       return this.state === IssuableStates.Opened;
     },
-    isWorkItemsEnabled() {
-      return this.glFeatures.workItems;
-    },
     showCsvButtons() {
       return this.isProject && this.isSignedIn;
     },
diff --git a/app/assets/javascripts/notebook/cells/markdown.vue b/app/assets/javascripts/notebook/cells/markdown.vue
index 127e046b5a9..9aa6abd9d8c 100644
--- a/app/assets/javascripts/notebook/cells/markdown.vue
+++ b/app/assets/javascripts/notebook/cells/markdown.vue
@@ -148,6 +148,11 @@ export default {
       type: Object,
       required: true,
     },
+    hidePrompt: {
+      type: Boolean,
+      required: false,
+      default: false,
+    },
   },
   computed: {
     markdown() {
@@ -163,7 +168,7 @@ export default {
 
 <template>
   <div class="cell text-cell">
-    <prompt />
+    <prompt v-if="!hidePrompt" />
     <div v-safe-html:[$options.markdownConfig]="markdown" class="markdown"></div>
   </div>
 </template>
diff --git a/app/assets/javascripts/notebook/cells/output/index.vue b/app/assets/javascripts/notebook/cells/output/index.vue
index 88d01ffa659..bd01534089e 100644
--- a/app/assets/javascripts/notebook/cells/output/index.vue
+++ b/app/assets/javascripts/notebook/cells/output/index.vue
@@ -3,6 +3,9 @@ import CodeOutput from '../code/index.vue';
 import HtmlOutput from './html.vue';
 import ImageOutput from './image.vue';
 import LatexOutput from './latex.vue';
+import MarkdownOutput from './markdown.vue';
+
+const TEXT_MARKDOWN = 'text/markdown';
 
 export default {
   props: {
@@ -35,6 +38,8 @@ export default {
         return 'text/latex';
       } else if (output.data['image/svg+xml']) {
         return 'image/svg+xml';
+      } else if (output.data[TEXT_MARKDOWN]) {
+        return TEXT_MARKDOWN;
       }
 
       return 'text/plain';
@@ -42,7 +47,7 @@ export default {
     dataForType(output, type) {
       let data = output.data[type];
 
-      if (typeof data === 'object') {
+      if (typeof data === 'object' && this.outputType(output) !== TEXT_MARKDOWN) {
         data = data.join('');
       }
 
@@ -61,6 +66,8 @@ export default {
         return LatexOutput;
       } else if (output.data['image/svg+xml']) {
         return HtmlOutput;
+      } else if (output.data[TEXT_MARKDOWN]) {
+        return MarkdownOutput;
       }
 
       return CodeOutput;
diff --git a/app/assets/javascripts/notebook/cells/output/markdown.vue b/app/assets/javascripts/notebook/cells/output/markdown.vue
new file mode 100644
index 00000000000..5da057dee72
--- /dev/null
+++ b/app/assets/javascripts/notebook/cells/output/markdown.vue
@@ -0,0 +1,42 @@
+<script>
+import { GlSafeHtmlDirective as SafeHtml } from '@gitlab/ui';
+import Prompt from '../prompt.vue';
+import Markdown from '../markdown.vue';
+
+export default {
+  name: 'MarkdownOutput',
+  components: {
+    Prompt,
+    Markdown,
+  },
+  directives: {
+    SafeHtml,
+  },
+  props: {
+    count: {
+      type: Number,
+      required: true,
+    },
+    rawCode: {
+      type: Array,
+      required: true,
+    },
+    index: {
+      type: Number,
+      required: true,
+    },
+  },
+  computed: {
+    markdownContent() {
+      return { source: this.rawCode };
+    },
+  },
+};
+</script>
+
+<template>
+  <div class="output">
+    <prompt type="Out" :count="count" :show-output="index === 0" />
+    <markdown :cell="markdownContent" :hide-prompt="true" />
+  </div>
+</template>
diff --git a/app/assets/javascripts/releases/components/app_edit_new.vue b/app/assets/javascripts/releases/components/app_edit_new.vue
index dd3f4ed636f..965b9fa09d6 100644
--- a/app/assets/javascripts/releases/components/app_edit_new.vue
+++ b/app/assets/javascripts/releases/components/app_edit_new.vue
@@ -257,9 +257,9 @@ export default {
 
       <asset-links-form />
 
-      <div class="d-flex pt-3">
+      <div class="d-flex gl-gap-x-3 pt-3">
         <gl-button
-          class="mr-auto js-no-auto-disable"
+          class="js-no-auto-disable"
           category="primary"
           variant="confirm"
           type="submit"
diff --git a/app/assets/javascripts/releases/components/asset_links_form.vue b/app/assets/javascripts/releases/components/asset_links_form.vue
index 7c6d44456d9..dc465851721 100644
--- a/app/assets/javascripts/releases/components/asset_links_form.vue
+++ b/app/assets/javascripts/releases/components/asset_links_form.vue
@@ -131,10 +131,10 @@ export default {
     <div
       v-for="(link, index) in release.assets.links"
       :key="link.id"
-      class="row flex-column flex-sm-row align-items-stretch align-items-sm-start no-gutters"
+      class="gl-sm-display-flex flex-column flex-sm-row gl-gap-5 align-items-stretch align-items-sm-start no-gutters"
     >
       <gl-form-group
-        class="url-field form-group col pr-sm-2"
+        class="url-field form-group col"
         :label="__('URL')"
         :label-for="`asset-url-${index}`"
       >
@@ -174,7 +174,7 @@ export default {
       </gl-form-group>
 
       <gl-form-group
-        class="link-title-field col px-sm-2"
+        class="link-title-field col"
         :label="__('Link title')"
         :label-for="`asset-link-name-${index}`"
       >
@@ -201,7 +201,7 @@ export default {
       </gl-form-group>
 
       <gl-form-group
-        class="link-type-field col-auto px-sm-2"
+        class="link-type-field col-auto"
         :label="__('Type')"
         :label-for="`asset-type-${index}`"
       >
@@ -216,9 +216,8 @@ export default {
         />
       </gl-form-group>
 
-      <div class="mb-5 mb-sm-3 mt-sm-4 col col-sm-auto pl-sm-2">
+      <div v-if="release.assets.links.length !== 1" class="mb-5 mb-sm-3 mt-sm-4 col col-sm-auto">
         <gl-button
-          v-gl-tooltip
           class="remove-button w-100 form-control"
           :aria-label="__('Remove asset link')"
           :title="__('Remove asset link')"
@@ -233,8 +232,9 @@ export default {
     </div>
     <gl-button
       ref="addAnotherLinkButton"
-      variant="link"
-      class="align-self-end mb-5 mb-sm-0"
+      category="secondary"
+      variant="confirm"
+      class="gl-align-self-start gl-mb-5"
       @click="onAddAnotherClicked"
     >
       {{ __('Add another link') }}
diff --git a/app/assets/javascripts/users_select/index.js b/app/assets/javascripts/users_select/index.js
index fbf7e0b3a86..7c1204c511c 100644
--- a/app/assets/javascripts/users_select/index.js
+++ b/app/assets/javascripts/users_select/index.js
@@ -67,6 +67,22 @@ function UsersSelect(currentUser, els, options = {}) {
     let assigneeTemplate;
     let collapsedAssigneeTemplate;
 
+    const suggestedReviewersHelpPath = $dropdown.data('suggestedReviewersHelpPath');
+    const suggestedReviewersHeaderTemplate = template(
+      `<div class="gl-display-flex gl-align-items-center">
+         <%- header %>
+         <a
+           title="${s__('SuggestedReviewers|Learn about suggested reviewers')}"
+           href="${suggestedReviewersHelpPath}"
+           rel="noopener"
+           target="_blank"
+           aria-label="${s__('SuggestedReviewers|Suggested reviewers help link')}"
+           class="gl-hover-bg-transparent! gl-p-0! has-tooltip">
+           ${spriteIcon('question-o', 'gl-ml-3 gl-icon s16')}
+         </a>
+       </div>`,
+    );
+
     if (selectedId === undefined) {
       selectedId = selectedIdDefault;
     }
@@ -383,7 +399,12 @@ function UsersSelect(currentUser, els, options = {}) {
         if (!suggestedUsers.length) return [];
 
         const items = [
-          { type: 'header', content: $dropdown.data('suggestedReviewersHeader') },
+          {
+            type: 'header',
+            content: suggestedReviewersHeaderTemplate({
+              header: $dropdown.data('suggestedReviewersHeader'),
+            }),
+          },
           ...suggestedUsers,
           { type: 'header', content: $dropdown.data('allMembersHeader') },
         ];
diff --git a/app/assets/javascripts/vue_merge_request_widget/components/widget/status_icon.vue b/app/assets/javascripts/vue_merge_request_widget/components/widget/status_icon.vue
index ff17de343d6..181b8cfad9a 100644
--- a/app/assets/javascripts/vue_merge_request_widget/components/widget/status_icon.vue
+++ b/app/assets/javascripts/vue_merge_request_widget/components/widget/status_icon.vue
@@ -34,8 +34,8 @@ export default {
     iconAriaLabel() {
       return `${capitalizeFirstCharacter(this.iconName)} ${this.name}`;
     },
-    iconSize() {
-      return this.level === 1 ? 16 : 12;
+    iconClassNameText() {
+      return this.$options.EXTENSION_ICON_CLASS[this.iconName];
     },
   },
   EXTENSION_ICON_NAMES,
@@ -44,24 +44,22 @@ export default {
 </script>
 
 <template>
-  <div :class="[$options.EXTENSION_ICON_CLASS[iconName]]" class="gl-mr-3">
+  <div
+    :class="{
+      [iconClassNameText]: !isLoading,
+      [`mr-widget-status-icon-level-${level}`]: !isLoading,
+      'gl-mr-3': level === 1,
+    }"
+    class="gl-relative gl-w-6 gl-h-6 gl-rounded-full gl--flex-center"
+  >
     <gl-loading-icon v-if="isLoading" size="md" inline />
-    <div
+    <gl-icon
       v-else
-      class="gl-display-flex gl-align-items-center gl-justify-content-center gl-rounded-full gl-bg-gray-10"
-      :class="{
-        'gl-p-2': level === 1,
-      }"
-    >
-      <div class="gl-rounded-full gl-bg-white">
-        <gl-icon
-          :name="$options.EXTENSION_ICON_NAMES[iconName]"
-          :size="iconSize"
-          :aria-label="iconAriaLabel"
-          :data-qa-selector="`status_${iconName}_icon`"
-          class="gl-display-block"
-        />
-      </div>
-    </div>
+      :name="$options.EXTENSION_ICON_NAMES[iconName]"
+      :size="12"
+      :aria-label="iconAriaLabel"
+      :data-qa-selector="`status_${iconName}_icon`"
+      class="gl-relative gl-z-index-1"
+    />
   </div>
 </template>
diff --git a/app/assets/javascripts/work_items_hierarchy/components/app.vue b/app/assets/javascripts/work_items_hierarchy/components/app.vue
index 779bd27516a..1eeb3abf4bd 100644
--- a/app/assets/javascripts/work_items_hierarchy/components/app.vue
+++ b/app/assets/javascripts/work_items_hierarchy/components/app.vue
@@ -25,7 +25,7 @@ export default {
     workItemTypes() {
       return this.workItemHierarchy.reduce(
         (itemTypes, item) => {
-          const skipItem = workItemTypes[item.type].isWorkItem && !window.gon?.features?.workItems;
+          const skipItem = workItemTypes[item.type].isWorkItem;
 
           if (skipItem) {
             return itemTypes;
diff --git a/app/assets/stylesheets/page_bundles/merge_requests.scss b/app/assets/stylesheets/page_bundles/merge_requests.scss
index 4a5143befc5..772a140d661 100644
--- a/app/assets/stylesheets/page_bundles/merge_requests.scss
+++ b/app/assets/stylesheets/page_bundles/merge_requests.scss
@@ -1085,6 +1085,31 @@ $tabs-holder-z-index: 250;
   border-top: 0;
 }
 
+.mr-widget-status-icon-level-1::before {
+  @include gl-content-empty;
+  @include gl-absolute;
+  @include gl-left-0;
+  @include gl-top-0;
+  @include gl-bottom-0;
+  @include gl-right-0;
+  @include gl-opacity-3;
+  @include gl-rounded-full;
+  @include gl-border-solid;
+  @include gl-border-4;
+}
+
+.mr-widget-status-icon-level-1::after {
+  @include gl-content-empty;
+  @include gl-absolute;
+  @include gl-rounded-full;
+  @include gl-border-solid;
+  @include gl-border-4;
+  @include gl-left-2;
+  @include gl-right-2;
+  @include gl-top-2;
+  @include gl-bottom-2;
+}
+
 .memory-graph-container {
   background: var(--white, $white);
   border: 1px solid var(--gray-100, $gray-100);
diff --git a/app/graphql/graphql_triggers.rb b/app/graphql/graphql_triggers.rb
index dc4f838ae36..710e7fe110c 100644
--- a/app/graphql/graphql_triggers.rb
+++ b/app/graphql/graphql_triggers.rb
@@ -25,6 +25,10 @@ module GraphqlTriggers
     GitlabSchema.subscriptions.trigger('issuableDatesUpdated', { issuable_id: issuable.to_gid }, issuable)
   end
 
+  def self.issuable_milestone_updated(issuable)
+    GitlabSchema.subscriptions.trigger('issuableMilestoneUpdated', { issuable_id: issuable.to_gid }, issuable)
+  end
+
   def self.merge_request_reviewers_updated(merge_request)
     GitlabSchema.subscriptions.trigger(
       'mergeRequestReviewersUpdated',
diff --git a/app/graphql/types/subscription_type.rb b/app/graphql/types/subscription_type.rb
index 3b8f5c64beb..9d5edec82b2 100644
--- a/app/graphql/types/subscription_type.rb
+++ b/app/graphql/types/subscription_type.rb
@@ -22,6 +22,9 @@ module Types
     field :issuable_dates_updated, subscription: Subscriptions::IssuableUpdated, null: true,
                                    description: 'Triggered when the due date or start date of an issuable is updated.'
 
+    field :issuable_milestone_updated, subscription: Subscriptions::IssuableUpdated, null: true,
+                                       description: 'Triggered when the milestone of an issuable is updated.'
+
     field :merge_request_reviewers_updated,
           subscription: Subscriptions::IssuableUpdated,
           null: true,
diff --git a/app/models/concerns/redis_cacheable.rb b/app/models/concerns/redis_cacheable.rb
index 2d4ed51ce3b..1d33ff9b79a 100644
--- a/app/models/concerns/redis_cacheable.rb
+++ b/app/models/concerns/redis_cacheable.rb
@@ -27,7 +27,7 @@ module RedisCacheable
 
   def cache_attributes(values)
     Gitlab::Redis::Cache.with do |redis|
-      redis.set(cache_attribute_key, values.to_json, ex: CACHED_ATTRIBUTES_EXPIRY_TIME)
+      redis.set(cache_attribute_key, Gitlab::Json.dump(values), ex: CACHED_ATTRIBUTES_EXPIRY_TIME)
     end
 
     clear_memoization(:cached_attributes)
diff --git a/app/models/diff_discussion.rb b/app/models/diff_discussion.rb
index f4d665cf279..041ec98ffc9 100644
--- a/app/models/diff_discussion.rb
+++ b/app/models/diff_discussion.rb
@@ -37,18 +37,18 @@ class DiffDiscussion < Discussion
 
   def reply_attributes
     super.merge(
-      original_position: original_position.to_json,
-      position: position.to_json
+      original_position: Gitlab::Json.dump(original_position),
+      position: Gitlab::Json.dump(position)
     )
   end
 
   def cache_key
-    positions_json = diff_note_positions.map { |dnp| dnp.position.to_json }
+    positions_json = diff_note_positions.map { |dnp| Gitlab::Json.dump(dnp.position) }
     positions_sha = Digest::SHA1.hexdigest(positions_json.join(':')) if positions_json.any?
 
     [
       super,
-      Digest::SHA1.hexdigest(position.to_json),
+      Digest::SHA1.hexdigest(Gitlab::Json.dump(position)),
       positions_sha
     ].join(':')
   end
diff --git a/app/models/integrations/assembla.rb b/app/models/integrations/assembla.rb
index a8f6e00b32c..536d5584bf6 100644
--- a/app/models/integrations/assembla.rb
+++ b/app/models/integrations/assembla.rb
@@ -35,7 +35,9 @@ module Integrations
       return unless supported_events.include?(data[:object_kind])
 
       url = "https://atlas.assembla.com/spaces/#{subdomain}/github_tool?secret_key=#{token}"
-      Gitlab::HTTP.post(url, body: { payload: data }.to_json, headers: { 'Content-Type' => 'application/json' })
+      body = { payload: data }
+
+      Gitlab::HTTP.post(url, body: Gitlab::Json.dump(body), headers: { 'Content-Type' => 'application/json' })
     end
   end
 end
diff --git a/app/models/integrations/pivotaltracker.rb b/app/models/integrations/pivotaltracker.rb
index d32fb974339..1acdbbbf9bc 100644
--- a/app/models/integrations/pivotaltracker.rb
+++ b/app/models/integrations/pivotaltracker.rb
@@ -56,7 +56,7 @@ module Integrations
         }
         Gitlab::HTTP.post(
           API_ENDPOINT,
-          body: message.to_json,
+          body: Gitlab::Json.dump(message),
           headers: {
             'Content-Type' => 'application/json',
             'X-TrackerToken' => token
diff --git a/app/models/integrations/pumble.rb b/app/models/integrations/pumble.rb
index 17026410eb1..6c5493c4b65 100644
--- a/app/models/integrations/pumble.rb
+++ b/app/models/integrations/pumble.rb
@@ -51,7 +51,7 @@ module Integrations
 
     def notify(message, opts)
       header = { 'Content-Type' => 'application/json' }
-      response = Gitlab::HTTP.post(webhook, headers: header, body: { text: message.summary }.to_json)
+      response = Gitlab::HTTP.post(webhook, headers: header, body: Gitlab::Json.dump({ text: message.summary }))
 
       response if response.success?
     end
diff --git a/app/models/integrations/unify_circuit.rb b/app/models/integrations/unify_circuit.rb
index f10a75fac5d..2e7b9b7dc60 100644
--- a/app/models/integrations/unify_circuit.rb
+++ b/app/models/integrations/unify_circuit.rb
@@ -43,11 +43,13 @@ module Integrations
     private
 
     def notify(message, opts)
-      response = Gitlab::HTTP.post(webhook, body: {
+      body = {
         subject: message.project_name,
         text: message.summary,
         markdown: true
-      }.to_json)
+      }
+
+      response = Gitlab::HTTP.post(webhook, body: Gitlab::Json.dump(body))
 
       response if response.success?
     end
diff --git a/app/models/integrations/webex_teams.rb b/app/models/integrations/webex_teams.rb
index 75be457dcf5..5a7a296f550 100644
--- a/app/models/integrations/webex_teams.rb
+++ b/app/models/integrations/webex_teams.rb
@@ -44,7 +44,7 @@ module Integrations
 
     def notify(message, opts)
       header = { 'Content-Type' => 'application/json' }
-      response = Gitlab::HTTP.post(webhook, headers: header, body: { markdown: message.summary }.to_json)
+      response = Gitlab::HTTP.post(webhook, headers: header, body: Gitlab::Json.dump({ markdown: message.summary }))
 
       response if response.success?
     end
diff --git a/app/models/iteration.rb b/app/models/iteration.rb
index ed73793c78f..c6269313d8b 100644
--- a/app/models/iteration.rb
+++ b/app/models/iteration.rb
@@ -4,9 +4,8 @@
 class Iteration < ApplicationRecord
   include IgnorableColumns
 
-  # TODO https://gitlab.com/gitlab-org/gitlab/-/issues/372125
   # TODO https://gitlab.com/gitlab-org/gitlab/-/issues/372126
-  ignore_column :project_id, remove_with: '15.6', remove_after: '2022-09-17'
+  ignore_column :project_id, remove_with: '15.7', remove_after: '2022-11-18'
 
   self.table_name = 'sprints'
 
diff --git a/app/models/merge_request_diff_commit.rb b/app/models/merge_request_diff_commit.rb
index 66f1e45fd49..152fb195c97 100644
--- a/app/models/merge_request_diff_commit.rb
+++ b/app/models/merge_request_diff_commit.rb
@@ -70,7 +70,7 @@ class MergeRequestDiffCommit < ApplicationRecord
         sha: Gitlab::Database::ShaAttribute.serialize(sha), # rubocop:disable Cop/ActiveRecordSerialize
         authored_date: Gitlab::Database.sanitize_timestamp(commit_hash[:authored_date]),
         committed_date: Gitlab::Database.sanitize_timestamp(commit_hash[:committed_date]),
-        trailers: commit_hash.fetch(:trailers, {}).to_json
+        trailers: Gitlab::Json.dump(commit_hash.fetch(:trailers, {}))
       )
     end
 
diff --git a/app/services/issues/update_service.rb b/app/services/issues/update_service.rb
index e5feb4422f6..0aed9e3ba40 100644
--- a/app/services/issues/update_service.rb
+++ b/app/services/issues/update_service.rb
@@ -163,6 +163,7 @@ module Issues
 
       invalidate_milestone_issue_counters(issue)
       send_milestone_change_notification(issue)
+      GraphqlTriggers.issuable_milestone_updated(issue)
     end
 
     def invalidate_milestone_issue_counters(issue)
diff --git a/app/views/shared/issuable/_sidebar_reviewers.html.haml b/app/views/shared/issuable/_sidebar_reviewers.html.haml
index c764cfff2fd..6bbd522a43b 100644
--- a/app/views/shared/issuable/_sidebar_reviewers.html.haml
+++ b/app/views/shared/issuable/_sidebar_reviewers.html.haml
@@ -31,6 +31,7 @@
   - data = { multi_select: true }
   - data['dropdown-title'] = title
   - data['dropdown-header'] = dropdown_options[:data][:'dropdown-header']
+  - data[:suggested_reviewers_help_path] = dropdown_options[:data][:suggested_reviewers_help_path]
   - data[:suggested_reviewers_header] = dropdown_options[:data][:suggested_reviewers_header]
   - data[:all_members_header] = dropdown_options[:data][:all_members_header]
   - data[:show_suggested] = dropdown_options[:data][:show_suggested]
diff --git a/config/initializers/hashie_mash_permitted_patch.rb b/config/initializers/hashie_mash_permitted_patch.rb
new file mode 100644
index 00000000000..b793a408c91
--- /dev/null
+++ b/config/initializers/hashie_mash_permitted_patch.rb
@@ -0,0 +1,53 @@
+# frozen_string_literal: true
+
+# Pulls logic from https://github.com/Maxim-Filimonov/hashie-forbidden_attributes so we could drop the dependency.
+# This gem is simply `Hashie::Mash` monkey patch to allow mass assignment bypassing `:permitted?` check.
+#
+# Reasons:
+# 1. The gem was last updated 5 years ago and does not have CI setup to test under the latest Ruby/Rails.
+# 2. There is a significant chance this logic is not used at all.
+# We didn't find any explicit places in the code where we mass-assign to `Hashie::Mash`.
+# Experimental MR where we dropped the gem showed that no tests from the full suite failed:
+# https://gitlab.com/gitlab-org/gitlab/-/merge_requests/101535
+# 3. The logic is very simple. Even if we need it, keeping it in our codebase is better than pulling a dependency.
+# This logic will be visible and it will be one less gem to install.
+#
+# Next steps:
+# 1. Keep the patch for at least one milestone in our codebase. Log its usage.
+# 2. After that, check if there were any related log events.
+# 3. If no usages were tracked, we could drop the patch (delete this file).
+# 4. Otherwise, audit where and why we need it, and add a comment to that place.
+#
+# See discussion https://gitlab.com/gitlab-org/gitlab/-/issues/378398#note_1143133426
+
+require 'hashie/mash'
+
+module Hashie
+  class Mash
+    module MonkeyPatch
+      def respond_to_missing?(method_name, *args)
+        if method_name == :permitted?
+          Gitlab::AppLogger.info(message: 'Hashie::Mash#respond_to?(:permitted?)',
+                                 caller: Gitlab::BacktraceCleaner.clean_backtrace(caller))
+
+          return false
+        end
+
+        super
+      end
+
+      def method_missing(method_name, *args)
+        if method_name == :permitted?
+          Gitlab::AppLogger.info(message: 'Hashie::Mash#permitted?',
+                                 caller: Gitlab::BacktraceCleaner.clean_backtrace(caller))
+
+          raise ArgumentError
+        end
+
+        super
+      end
+    end
+
+    prepend MonkeyPatch
+  end
+end
diff --git a/config/open_api.yml b/config/open_api.yml
index 82a972e39bd..d7a170f2a22 100644
--- a/config/open_api.yml
+++ b/config/open_api.yml
@@ -18,5 +18,7 @@ metadata:
     description: Operations related to metadata of the GitLab instance
   - name: access_requests
     description: Operations related to access requests
+  - name: merge_requests
+    description: Operations related to merge requests
   - name: deployments
     description: Operations related to deployments
diff --git a/db/migrate/20210305031822_create_dast_site_profile_variables.rb b/db/migrate/20210305031822_create_dast_site_profile_variables.rb
index f55755aa731..4b8fc982d86 100644
--- a/db/migrate/20210305031822_create_dast_site_profile_variables.rb
+++ b/db/migrate/20210305031822_create_dast_site_profile_variables.rb
@@ -13,7 +13,7 @@ class CreateDastSiteProfileVariables < ActiveRecord::Migration[6.0]
     encrypted_value_constraint_name = check_constraint_name(:dast_site_profile_secret_variables, 'encrypted_value', 'max_length')
     encrypted_value_iv_constraint_name = check_constraint_name(:dast_site_profile_secret_variables, 'encrypted_value_iv', 'max_length')
 
-    create_table_with_constraints :dast_site_profile_secret_variables, comment: table_comment.to_json do |t|
+    create_table_with_constraints :dast_site_profile_secret_variables, comment: Gitlab::Json.dump(table_comment) do |t|
       t.references :dast_site_profile, null: false, foreign_key: { on_delete: :cascade }, index: false
 
       t.timestamps_with_timezone
diff --git a/db/migrate/20210317035357_create_dast_profiles_pipelines.rb b/db/migrate/20210317035357_create_dast_profiles_pipelines.rb
index f7a29958f12..f84e1237643 100644
--- a/db/migrate/20210317035357_create_dast_profiles_pipelines.rb
+++ b/db/migrate/20210317035357_create_dast_profiles_pipelines.rb
@@ -6,7 +6,7 @@ class CreateDastProfilesPipelines < ActiveRecord::Migration[6.0]
   def up
     table_comment = { owner: 'group::dynamic analysis', description: 'Join table between DAST Profiles and CI Pipelines' }
 
-    create_table :dast_profiles_pipelines, primary_key: [:dast_profile_id, :ci_pipeline_id], comment: table_comment.to_json do |t|
+    create_table :dast_profiles_pipelines, primary_key: [:dast_profile_id, :ci_pipeline_id], comment: Gitlab::Json.dump(table_comment) do |t|
       t.bigint :dast_profile_id, null: false
       t.bigint :ci_pipeline_id, null: false
 
diff --git a/db/migrate/20210412111213_create_security_orchestration_policy_rule_schedule.rb b/db/migrate/20210412111213_create_security_orchestration_policy_rule_schedule.rb
index c7035400cba..365fa36f11b 100644
--- a/db/migrate/20210412111213_create_security_orchestration_policy_rule_schedule.rb
+++ b/db/migrate/20210412111213_create_security_orchestration_policy_rule_schedule.rb
@@ -11,7 +11,7 @@ class CreateSecurityOrchestrationPolicyRuleSchedule < ActiveRecord::Migration[6.
   def up
     table_comment = { owner: 'group::container security', description: 'Schedules used to store relationship between project and security policy repository' }
 
-    create_table_with_constraints :security_orchestration_policy_rule_schedules, comment: table_comment.to_json do |t|
+    create_table_with_constraints :security_orchestration_policy_rule_schedules, comment: Gitlab::Json.dump(table_comment) do |t|
       t.timestamps_with_timezone
       t.datetime_with_timezone :next_run_at, null: true
 
diff --git a/db/migrate/20210423054022_create_dast_site_profiles_pipelines.rb b/db/migrate/20210423054022_create_dast_site_profiles_pipelines.rb
index bbdb4f02ab4..80b97ff5afe 100644
--- a/db/migrate/20210423054022_create_dast_site_profiles_pipelines.rb
+++ b/db/migrate/20210423054022_create_dast_site_profiles_pipelines.rb
@@ -4,7 +4,7 @@ class CreateDastSiteProfilesPipelines < ActiveRecord::Migration[6.0]
   def up
     table_comment = { owner: 'group::dynamic analysis', description: 'Join table between DAST Site Profiles and CI Pipelines' }
 
-    create_table :dast_site_profiles_pipelines, primary_key: [:dast_site_profile_id, :ci_pipeline_id], comment: table_comment.to_json do |t|
+    create_table :dast_site_profiles_pipelines, primary_key: [:dast_site_profile_id, :ci_pipeline_id], comment: Gitlab::Json.dump(table_comment) do |t|
       t.bigint :dast_site_profile_id, null: false
       t.bigint :ci_pipeline_id, null: false
 
diff --git a/db/migrate/20210604032738_create_dast_site_profiles_builds.rb b/db/migrate/20210604032738_create_dast_site_profiles_builds.rb
index 2e9eb2c7cb7..6e653b36787 100644
--- a/db/migrate/20210604032738_create_dast_site_profiles_builds.rb
+++ b/db/migrate/20210604032738_create_dast_site_profiles_builds.rb
@@ -4,7 +4,7 @@ class CreateDastSiteProfilesBuilds < ActiveRecord::Migration[6.1]
   def up
     table_comment = { owner: 'group::dynamic analysis', description: 'Join table between DAST Site Profiles and CI Builds' }
 
-    create_table :dast_site_profiles_builds, primary_key: [:dast_site_profile_id, :ci_build_id], comment: table_comment.to_json do |t|
+    create_table :dast_site_profiles_builds, primary_key: [:dast_site_profile_id, :ci_build_id], comment: Gitlab::Json.dump(table_comment) do |t|
       t.bigint :dast_site_profile_id, null: false
       t.bigint :ci_build_id, null: false
 
diff --git a/db/migrate/20210604051330_create_dast_scanner_profiles_builds.rb b/db/migrate/20210604051330_create_dast_scanner_profiles_builds.rb
index f8a5f735f0d..0fe3ada4c0d 100644
--- a/db/migrate/20210604051330_create_dast_scanner_profiles_builds.rb
+++ b/db/migrate/20210604051330_create_dast_scanner_profiles_builds.rb
@@ -4,7 +4,7 @@ class CreateDastScannerProfilesBuilds < ActiveRecord::Migration[6.1]
   def up
     table_comment = { owner: 'group::dynamic analysis', description: 'Join table between DAST Scanner Profiles and CI Builds' }
 
-    create_table :dast_scanner_profiles_builds, primary_key: [:dast_scanner_profile_id, :ci_build_id], comment: table_comment.to_json do |t|
+    create_table :dast_scanner_profiles_builds, primary_key: [:dast_scanner_profile_id, :ci_build_id], comment: Gitlab::Json.dump(table_comment) do |t|
       t.bigint :dast_scanner_profile_id, null: false
       t.bigint :ci_build_id, null: false
 
diff --git a/db/migrate/20210713123345_create_dast_profile_schedule.rb b/db/migrate/20210713123345_create_dast_profile_schedule.rb
index 951aab63579..ea660de572a 100644
--- a/db/migrate/20210713123345_create_dast_profile_schedule.rb
+++ b/db/migrate/20210713123345_create_dast_profile_schedule.rb
@@ -10,7 +10,7 @@ class CreateDastProfileSchedule < ActiveRecord::Migration[6.1]
       owner: 'group::dynamic analysis', description: 'Scheduling for scans using DAST Profiles'
     }
 
-    create_table_with_constraints :dast_profile_schedules, comment: table_comment.to_json do |t|
+    create_table_with_constraints :dast_profile_schedules, comment: Gitlab::Json.dump(table_comment) do |t|
       t.bigint :project_id, null: false
       t.bigint :dast_profile_id, null: false
       t.bigint :user_id
diff --git a/db/post_migrate/20210311120155_backfill_events_id_for_bigint_conversion.rb b/db/post_migrate/20210311120155_backfill_events_id_for_bigint_conversion.rb
index b9427f7cc93..5d31cdb05e6 100644
--- a/db/post_migrate/20210311120155_backfill_events_id_for_bigint_conversion.rb
+++ b/db/post_migrate/20210311120155_backfill_events_id_for_bigint_conversion.rb
@@ -19,7 +19,7 @@ class BackfillEventsIdForBigintConversion < ActiveRecord::Migration[6.0]
     Gitlab::Database::BackgroundMigration::BatchedMigration
       .where(job_class_name: 'CopyColumnUsingBackgroundMigrationJob')
       .where(table_name: 'events', column_name: 'id')
-      .where(job_arguments: %w[id id_convert_to_bigint].to_json)
+      .where(job_arguments: Gitlab::Json.dump(%w[id id_convert_to_bigint]))
       .delete_all
   end
 
diff --git a/db/post_migrate/20210311120156_backfill_push_event_payload_event_id_for_bigint_conversion.rb b/db/post_migrate/20210311120156_backfill_push_event_payload_event_id_for_bigint_conversion.rb
index 0d610f1dde1..b64282fe0d3 100644
--- a/db/post_migrate/20210311120156_backfill_push_event_payload_event_id_for_bigint_conversion.rb
+++ b/db/post_migrate/20210311120156_backfill_push_event_payload_event_id_for_bigint_conversion.rb
@@ -20,7 +20,7 @@ class BackfillPushEventPayloadEventIdForBigintConversion < ActiveRecord::Migrati
     Gitlab::Database::BackgroundMigration::BatchedMigration
       .where(job_class_name: 'CopyColumnUsingBackgroundMigrationJob')
       .where(table_name: 'push_event_payloads', column_name: 'event_id')
-      .where(job_arguments: %w[event_id event_id_convert_to_bigint].to_json)
+      .where(job_arguments: Gitlab::Json.dump(%w[event_id event_id_convert_to_bigint]))
       .delete_all
   end
 
diff --git a/db/post_migrate/20210415101228_backfill_ci_build_needs_for_bigint_conversion.rb b/db/post_migrate/20210415101228_backfill_ci_build_needs_for_bigint_conversion.rb
index 1ee67cd9dda..8fcaeb3fb04 100644
--- a/db/post_migrate/20210415101228_backfill_ci_build_needs_for_bigint_conversion.rb
+++ b/db/post_migrate/20210415101228_backfill_ci_build_needs_for_bigint_conversion.rb
@@ -20,7 +20,7 @@ class BackfillCiBuildNeedsForBigintConversion < ActiveRecord::Migration[6.0]
     Gitlab::Database::BackgroundMigration::BatchedMigration
       .where(job_class_name: 'CopyColumnUsingBackgroundMigrationJob')
       .where(table_name: 'ci_build_needs', column_name: 'build_id')
-      .where(job_arguments: %w[build_id build_id_convert_to_bigint].to_json)
+      .where(job_arguments: Gitlab::Json.dump(%w[build_id build_id_convert_to_bigint]))
       .delete_all
   end
 
diff --git a/db/post_migrate/20210420121149_backfill_conversion_of_ci_job_artifacts.rb b/db/post_migrate/20210420121149_backfill_conversion_of_ci_job_artifacts.rb
index 67076cc647a..0c68834f723 100644
--- a/db/post_migrate/20210420121149_backfill_conversion_of_ci_job_artifacts.rb
+++ b/db/post_migrate/20210420121149_backfill_conversion_of_ci_job_artifacts.rb
@@ -19,7 +19,7 @@ class BackfillConversionOfCiJobArtifacts < ActiveRecord::Migration[6.0]
     Gitlab::Database::BackgroundMigration::BatchedMigration
       .where(job_class_name: 'CopyColumnUsingBackgroundMigrationJob')
       .where(table_name: 'ci_job_artifacts', column_name: 'id')
-      .where(job_arguments: [%w[id job_id], %w[id_convert_to_bigint job_id_convert_to_bigint]].to_json)
+      .where(job_arguments: Gitlab::Json.dump([%w[id job_id], %w[id_convert_to_bigint job_id_convert_to_bigint]]))
       .delete_all
   end
 
diff --git a/db/post_migrate/20210422023046_backfill_ci_sources_pipelines_source_job_id_for_bigint_conversion.rb b/db/post_migrate/20210422023046_backfill_ci_sources_pipelines_source_job_id_for_bigint_conversion.rb
index bde91473ee3..3c6f2385f1d 100644
--- a/db/post_migrate/20210422023046_backfill_ci_sources_pipelines_source_job_id_for_bigint_conversion.rb
+++ b/db/post_migrate/20210422023046_backfill_ci_sources_pipelines_source_job_id_for_bigint_conversion.rb
@@ -18,7 +18,7 @@ class BackfillCiSourcesPipelinesSourceJobIdForBigintConversion < ActiveRecord::M
     Gitlab::Database::BackgroundMigration::BatchedMigration
       .where(job_class_name: 'CopyColumnUsingBackgroundMigrationJob')
       .where(table_name: 'ci_sources_pipelines', column_name: 'id')
-      .where(job_arguments: [%w[source_job_id], %w[source_job_id_convert_to_bigint]].to_json)
+      .where(job_arguments: Gitlab::Json.dump([%w[source_job_id], %w[source_job_id_convert_to_bigint]]))
       .delete_all
   end
 
diff --git a/db/post_migrate/20210615234935_fix_batched_migrations_old_format_job_arguments.rb b/db/post_migrate/20210615234935_fix_batched_migrations_old_format_job_arguments.rb
index 535f7426938..818aea39762 100644
--- a/db/post_migrate/20210615234935_fix_batched_migrations_old_format_job_arguments.rb
+++ b/db/post_migrate/20210615234935_fix_batched_migrations_old_format_job_arguments.rb
@@ -17,8 +17,8 @@ class FixBatchedMigrationsOldFormatJobArguments < ActiveRecord::Migration[6.1]
 
       # rubocop:disable Rails/WhereEquals
       base_scope
-        .where('job_arguments = ?', legacy_job_arguments.to_json)
-        .where('NOT EXISTS (?)', base_scope.select('1').where('job_arguments = ?', current_job_arguments.to_json))
+        .where('job_arguments = ?', Gitlab::Json.dump(legacy_job_arguments))
+        .where('NOT EXISTS (?)', base_scope.select('1').where('job_arguments = ?', Gitlab::Json.dump(current_job_arguments)))
         .update_all(job_arguments: current_job_arguments)
       # rubocop:enable Rails/WhereEquals
     end
diff --git a/db/post_migrate/20221006172302_adjust_task_note_rename_background_migration_values.rb b/db/post_migrate/20221006172302_adjust_task_note_rename_background_migration_values.rb
index 2af16fb6d3c..b582b163e2d 100644
--- a/db/post_migrate/20221006172302_adjust_task_note_rename_background_migration_values.rb
+++ b/db/post_migrate/20221006172302_adjust_task_note_rename_background_migration_values.rb
@@ -20,7 +20,7 @@ class AdjustTaskNoteRenameBackgroundMigrationValues < Gitlab::Database::Migratio
 
     scope :for_configuration, ->(job_class_name, table_name, column_name, job_arguments) do
       where(job_class_name: job_class_name, table_name: table_name, column_name: column_name)
-        .where("job_arguments = ?", job_arguments.to_json) # rubocop:disable Rails/WhereEquals
+        .where("job_arguments = ?", Gitlab::Json.dump(job_arguments)) # rubocop:disable Rails/WhereEquals
     end
   end
 
diff --git a/db/post_migrate/20221024034228_remove_sprints_project_id_column.rb b/db/post_migrate/20221024034228_remove_sprints_project_id_column.rb
new file mode 100644
index 00000000000..e30d6dce497
--- /dev/null
+++ b/db/post_migrate/20221024034228_remove_sprints_project_id_column.rb
@@ -0,0 +1,38 @@
+# frozen_string_literal: true
+
+class RemoveSprintsProjectIdColumn < Gitlab::Database::Migration[2.0]
+  disable_ddl_transaction!
+
+  DATERANGE_CONSTRAINT_NAME = 'iteration_start_and_due_daterange_project_id_constraint'
+
+  def up
+    with_lock_retries do
+      remove_column :sprints, :project_id, :bigint if column_exists?(:sprints, :project_id)
+    end
+  end
+
+  def down
+    with_lock_retries do
+      add_column :sprints, :project_id, :bigint unless column_exists?(:sprints, :project_id)
+    end
+
+    with_lock_retries do
+      next if check_constraint_exists?(:sprints, DATERANGE_CONSTRAINT_NAME)
+
+      execute(<<~SQL)
+        ALTER TABLE sprints
+        ADD CONSTRAINT #{DATERANGE_CONSTRAINT_NAME}
+          EXCLUDE USING gist (project_id WITH =, daterange(start_date, due_date, '[]'::text) WITH &&)
+          WHERE (project_id IS NOT NULL)
+      SQL
+    end
+
+    add_check_constraint(:sprints,
+      'project_id <> NULL::bigint AND group_id IS NULL OR group_id <> NULL::bigint AND project_id IS NULL',
+      'sprints_must_belong_to_project_or_group')
+
+    add_concurrent_index :sprints, [:project_id, :iid], unique: true, name: 'index_sprints_on_project_id_and_iid'
+
+    add_concurrent_foreign_key :sprints, :projects, column: :project_id, on_delete: :cascade
+  end
+end
diff --git a/db/schema_migrations/20221024034228 b/db/schema_migrations/20221024034228
new file mode 100644
index 00000000000..3df637a8198
--- /dev/null
+++ b/db/schema_migrations/20221024034228
@@ -0,0 +1 @@
+7f83a1d04357f4f2e1e4ed92e0d9b0041f79d1850b28f41cee45d243e25741f0
\ No newline at end of file
diff --git a/db/structure.sql b/db/structure.sql
index 9d295fb6cb0..bfb0c9b0a24 100644
--- a/db/structure.sql
+++ b/db/structure.sql
@@ -21594,7 +21594,6 @@ CREATE TABLE sprints (
     updated_at timestamp with time zone NOT NULL,
     start_date date,
     due_date date,
-    project_id bigint,
     group_id bigint,
     iid integer NOT NULL,
     cached_markdown_version integer,
@@ -21605,7 +21604,6 @@ CREATE TABLE sprints (
     state_enum smallint DEFAULT 1 NOT NULL,
     iterations_cadence_id integer,
     sequence integer,
-    CONSTRAINT sprints_must_belong_to_project_or_group CHECK ((((project_id <> NULL::bigint) AND (group_id IS NULL)) OR ((group_id <> NULL::bigint) AND (project_id IS NULL)))),
     CONSTRAINT sprints_title CHECK ((char_length(title) <= 255))
 );
 
@@ -25863,9 +25861,6 @@ ALTER TABLE ONLY issues_self_managed_prometheus_alert_events
 ALTER TABLE ONLY sprints
     ADD CONSTRAINT iteration_start_and_due_date_iterations_cadence_id_constraint EXCLUDE USING gist (iterations_cadence_id WITH =, daterange(start_date, due_date, '[]'::text) WITH &&) WHERE ((group_id IS NOT NULL)) DEFERRABLE INITIALLY DEFERRED;
 
-ALTER TABLE ONLY sprints
-    ADD CONSTRAINT iteration_start_and_due_daterange_project_id_constraint EXCLUDE USING gist (project_id WITH =, daterange(start_date, due_date, '[]'::text) WITH &&) WHERE ((project_id IS NOT NULL));
-
 ALTER TABLE ONLY iterations_cadences
     ADD CONSTRAINT iterations_cadences_pkey PRIMARY KEY (id);
 
@@ -30569,8 +30564,6 @@ CREATE INDEX index_sprints_on_due_date ON sprints USING btree (due_date);
 
 CREATE INDEX index_sprints_on_group_id ON sprints USING btree (group_id);
 
-CREATE UNIQUE INDEX index_sprints_on_project_id_and_iid ON sprints USING btree (project_id, iid);
-
 CREATE INDEX index_sprints_on_title ON sprints USING btree (title);
 
 CREATE INDEX index_sprints_on_title_trigram ON sprints USING gin (title gin_trgm_ops);
@@ -33405,9 +33398,6 @@ ALTER TABLE ONLY namespaces
 ALTER TABLE ONLY fork_networks
     ADD CONSTRAINT fk_e7b436b2b5 FOREIGN KEY (root_project_id) REFERENCES projects(id) ON DELETE SET NULL;
 
-ALTER TABLE ONLY sprints
-    ADD CONSTRAINT fk_e8206c9686 FOREIGN KEY (project_id) REFERENCES projects(id) ON DELETE CASCADE;
-
 ALTER TABLE ONLY application_settings
     ADD CONSTRAINT fk_e8a145f3a7 FOREIGN KEY (instance_administrators_group_id) REFERENCES namespaces(id) ON DELETE SET NULL;
 
diff --git a/doc/ci/pipelines/img/merge_train_cancel_v12_0.png b/doc/ci/pipelines/img/merge_train_cancel_v12_0.png
deleted file mode 100644
index d7720ac1143..00000000000
--- a/doc/ci/pipelines/img/merge_train_cancel_v12_0.png
+++ /dev/null
diff --git a/doc/ci/pipelines/img/merge_train_failure.png b/doc/ci/pipelines/img/merge_train_failure.png
deleted file mode 100644
index 8a795fff432..00000000000
--- a/doc/ci/pipelines/img/merge_train_failure.png
+++ /dev/null
diff --git a/doc/ci/pipelines/img/merge_train_immediate_merge_v12_6.png b/doc/ci/pipelines/img/merge_train_immediate_merge_v12_6.png
deleted file mode 100644
index 7b903716a3d..00000000000
--- a/doc/ci/pipelines/img/merge_train_immediate_merge_v12_6.png
+++ /dev/null
diff --git a/doc/ci/pipelines/img/merge_train_position_v12_0.png b/doc/ci/pipelines/img/merge_train_position_v12_0.png
deleted file mode 100644
index ec4b157d428..00000000000
--- a/doc/ci/pipelines/img/merge_train_position_v12_0.png
+++ /dev/null
diff --git a/doc/ci/pipelines/img/merge_train_start_v12_0.png b/doc/ci/pipelines/img/merge_train_start_v12_0.png
deleted file mode 100644
index a4d0c8cf0e6..00000000000
--- a/doc/ci/pipelines/img/merge_train_start_v12_0.png
+++ /dev/null
diff --git a/doc/ci/pipelines/img/merge_train_start_when_pipeline_succeeds_v12_0.png b/doc/ci/pipelines/img/merge_train_start_when_pipeline_succeeds_v12_0.png
deleted file mode 100644
index 45762b8e85e..00000000000
--- a/doc/ci/pipelines/img/merge_train_start_when_pipeline_succeeds_v12_0.png
+++ /dev/null
diff --git a/doc/ci/pipelines/merge_trains.md b/doc/ci/pipelines/merge_trains.md
index c501d2a7904..370d81dacc4 100644
--- a/doc/ci/pipelines/merge_trains.md
+++ b/doc/ci/pipelines/merge_trains.md
@@ -6,253 +6,245 @@ info: To determine the technical writer assigned to the Stage/Group associated w
 
 # Merge trains **(PREMIUM)**
 
-> - [Introduced](https://gitlab.com/gitlab-org/gitlab/-/issues/9186) in GitLab 12.0.
-> - [Squash and merge](../../user/project/merge_requests/squash_and_merge.md) support [introduced](https://gitlab.com/gitlab-org/gitlab/-/issues/13001) in GitLab 12.6.
+Use merge trains to queue merge requests and verify their changes work together before
+they are merged to the target branch.
 
-For more information about why you might want to use merge trains, read [How starting merge trains improve efficiency for DevOps](https://about.gitlab.com/blog/2020/01/30/all-aboard-merge-trains/).
+In projects with frequent merges to the default branch, changes in different merge requests
+might conflict with each other. [Merged results pipelines](merged_results_pipelines.md)
+ensure the changes work with the content in the default branch, but not content
+that others are merging at the same time.
 
-When [merged results pipelines](merged_results_pipelines.md) are
-enabled, the pipeline jobs run as if the changes from your source branch have already
-been merged into the target branch.
+Merge trains do not work with [Semi-linear history merge requests](../../user/project/merge_requests/methods/index.md#merge-commit-with-semi-linear-history)
+or [fast-forward merge requests](../../user/project/merge_requests/methods/index.md#fast-forward-merge).
 
-However, the target branch may be changing rapidly. When you're ready to merge,
-if you haven't run the pipeline in a while, the target branch may have already changed.
-Merging now could introduce breaking changes.
+For more information about:
 
-*Merge trains* can prevent this from happening. A merge train is a queued list of merge
-requests, each waiting to be merged into the target branch.
+- How merge trains work, review the [merge train workflow](#merge-train-workflow).
+- Why you might want to use merge trains, read [How starting merge trains improve efficiency for DevOps](https://about.gitlab.com/blog/2020/01/30/all-aboard-merge-trains/).
 
-Many merge requests can be added to the train. Each merge request runs its own merged results pipeline,
-which includes the changes from all of the other merge requests in *front* of it on the train.
-All the pipelines run in parallel, to save time. The author of the internal merged result commit is always the user that initiated the merge.
+## Merge train workflow
 
-If the pipeline for a merge request fails, the breaking changes are not merged, and the target
-branch is unaffected. The merge request is removed from the train, and all pipelines behind it restart.
+A merge train starts when there are no merge requests waiting to merge and you
+select [**Start merge train**](#start-a-merge-train). GitLab starts a merge train pipeline
+that verifies that the changes can merge into the default branch. This first pipeline
+is the same as a [merged results pipeline](merged_results_pipelines.md), which runs on
+the changes of the source and target branches combined together. The author of the
+internal merged result commit is the user that initiated the merge.
 
-If the pipeline for the merge request at the front of the train completes successfully,
-the changes are merged into the target branch, and the other pipelines continue to
-run.
+To queue a second merge request to merge immediately after the first pipeline completes, select
+[**Add to merge train**](#add-a-merge-request-to-a-merge-train) and add it to the train.
+This second merge train pipeline runs on the changes of _both_ merge requests combined with the
+target branch. Similarly, if you add a third merge request, that pipeline runs on the changes
+of all three merge requests merged with the target branch. The pipelines all run in parallel.
 
-To add a merge request to a merge train, you need [permissions](../../user/permissions.md) to merge or push to the
-target branch.
+Each merge request merges into the target branch only after:
 
-Each merge train can run a maximum of **twenty** pipelines in parallel.
-If more than twenty merge requests are added to the merge train, the merge requests
-are queued until a slot in the merge train is free. There is no limit to the
-number of merge requests that can be queued.
+- The merge request's pipeline completes successfully.
+- All other merge requests queued before it are merged.
 
-## Merge train example
+If a merge train pipeline fails, the merge request is not merged. GitLab
+removes that merge request from the merge train, and starts new pipelines for all
+the merge requests that were queued after it.
 
-Three merge requests (`A`, `B` and `C`) are added to a merge train in order, which
+For example:
+
+Three merge requests (`A`, `B`, and `C`) are added to a merge train in order, which
 creates three merged results pipelines that run in parallel:
 
 1. The first pipeline runs on the changes from `A` combined with the target branch.
 1. The second pipeline runs on the changes from `A` and `B` combined with the target branch.
 1. The third pipeline runs on the changes from `A`, `B`, and `C` combined with the target branch.
 
-If the pipeline for `B` fails, it is removed from the train. The pipeline for
-`C` restarts with the `A` and `C` changes, but without the `B` changes.
+If the pipeline for `B` fails:
+
+- The first pipeline (`A`) continues to run.
+- `B` is removed from the train.
+- The pipeline for `C` [is cancelled](#automatic-pipeline-cancellation), and a new pipeline
+  starts for the changes from `A` and `C` combined with the target branch (without the `B` changes).
 
 If `A` then completes successfully, it merges into the target branch, and `C` continues
-to run. If more merge requests are added to the train, they now include the `A`
-changes that are included in the target branch, and the `C` changes that are from
-the merge request already in the train.
+to run. Any new merge requests added to the train include the `A` changes now in
+the target branch, and the `C` changes from the merge train.
 
 <i class="fa fa-youtube-play youtube" aria-hidden="true"></i>
-Watch this video for a demonstration on
-[how parallel execution of merge trains can prevent commits from breaking the default branch](https://www.youtube.com/watch?v=D4qCqXgZkHQ).
+Watch this video for a demonstration on [how parallel execution of merge trains can prevent commits from breaking the default branch](https://www.youtube.com/watch?v=D4qCqXgZkHQ).
 
-## Prerequisites
+### Automatic pipeline cancellation
 
-To enable merge trains:
+GitLab CI/CD detects redundant pipelines, and cancels them to conserve resources.
 
-- You must have the Maintainer role.
-- You must be using [GitLab Runner](https://gitlab.com/gitlab-org/gitlab-runner) 11.9 or later.
-- Your repository must be a GitLab repository, not an
-  [external repository](../ci_cd_for_external_repos/index.md).
+Redundant merge train pipelines happen when:
 
-Merge trains do not work with [Semi-linear history merge requests](../../user/project/merge_requests/methods/index.md#merge-commit-with-semi-linear-history)
-or [fast-forward merge requests](../../user/project/merge_requests/methods/index.md#fast-forward-merge).
+- The pipeline fails for one of the merge requests in the merge train.
+- You [skip the merge train and merge immediately](#skip-the-merge-train-and-merge-immediately).
+- You [remove a merge request from a merge train](#remove-a-merge-request-from-a-merge-train).
+
+In these cases, GitLab must create new merge train pipelines for some or all of the
+merge requests on the train. The old pipelines were comparing against the previous
+combined changes in the merge train, which are no longer valid, so these old pipelines
+are cancelled.
 
 ## Enable merge trains
 
-To enable merge trains for your project:
+Prerequisites:
+
+- You must have the Maintainer role.
+- Your repository must be a GitLab repository, not an [external repository](../ci_cd_for_external_repos/index.md).
+- Your pipeline must be [configured to use merge request pipelines](merge_request_pipelines.md#prerequisites).
+  Otherwise your merge requests may become stuck in an unresolved state or your pipelines
+  might be dropped.
+
+To enable merge trains:
 
-1. If you are on a self-managed GitLab instance, ensure the [feature flag](#merge-trains-feature-flag) is set correctly.
-1. [Configure your CI/CD configuration file](merge_request_pipelines.md#prerequisites)
-   so that the pipeline or individual jobs run for merge requests.
 1. On the top bar, select **Main menu > Projects** and find your project.
 1. On the left sidebar, select **Settings > Merge requests**.
 1. In the **Merge method** section, verify that **Merge commit** is selected.
-1. In the **Merge options** section, select **Enable merged results pipelines** (if not already selected) and **Enable merge trains**.
+1. In the **Merge options** section:
+   - In GitLab 13.6 and later, select **Enable merged results pipelines** and **Enable merge trains**.
+   - In GitLab 13.5 and earlier, select **Enable merge trains and pipelines for merged results**.
+     Additionally, [a feature flag](#disable-merge-trains-in-gitlab-135-and-earlier)
+     must be set correctly.
 1. Select **Save changes**.
 
-In GitLab 13.5 and earlier, there is only one checkbox, named
-**Enable merge trains and pipelines for merged results**.
+## Start a merge train
 
-WARNING:
-If you select the checkbox but don't configure your CI/CD to use
-merge request pipelines, your merge requests may become stuck in an
-unresolved state or your pipelines may be dropped.
+Prerequisites:
 
-## Start a merge train
+- You must have [permissions](../../user/permissions.md) to merge or push to the target branch.
 
 To start a merge train:
 
 1. Visit a merge request.
-1. Select **Start merge train**.
+1. Select:
+   - When no pipeline is running, **Start merge train**.
+   - When a pipeline is running, **Start merge train when pipeline succeeds**.
 
-![Start merge train](img/merge_train_start_v12_0.png)
+The merge request's merge train status displays under the pipeline widget with a
+message similar to `A new merge train has started and this merge request is the first of the queue.`
 
 Other merge requests can now be added to the train.
 
 ## Add a merge request to a merge train
 
+Prerequisites:
+
+- You must have [permissions](../../user/permissions.md) to merge or push to the target branch.
+
 To add a merge request to a merge train:
 
 1. Visit a merge request.
-1. Select **Add to merge train**.
+1. Select:
+   - When no pipeline is running, **Add to merge train**.
+   - When a pipeline is running, **Add to merge train when pipeline succeeds**.
 
-If pipelines are already running for the merge request, you cannot add the merge request
-to the train. Instead, you can schedule to add the merge request to a merge train **when the latest
-pipeline succeeds**.
+The merge request's merge train status displays under the pipeline widget with a
+message similar to `Added to the merge train. There are 2 merge requests waiting to be merged.`
 
-![Add to merge train when pipeline succeeds](img/merge_train_start_when_pipeline_succeeds_v12_0.png)
+Each merge train can run a maximum of twenty pipelines in parallel. If you add more than
+twenty merge requests to the merge train, the extra merge requests are queued, waiting
+for pipelines to complete. There is no limit to the number of queued merge requests
+waiting to join the merge train.
 
 ## Remove a merge request from a merge train
 
-1. Visit a merge request.
-1. Select **Remove from merge train**.
-
-![Cancel merge train](img/merge_train_cancel_v12_0.png)
+To remove a merge request from a merge train, select **Remove from merge train**.
+You can add the merge request to a merge train again later.
 
-If you want to add the merge request to a merge train again later, you can.
+When you remove a merge request from a merge train:
 
-## View a merge request's current position on the merge train
+- All pipelines for merge requests queued after the removed merge request restart.
+- Redundant pipelines [are cancelled](#automatic-pipeline-cancellation).
 
-After a merge request has been added to the merge train, the merge request's
-current position is displayed under the pipeline widget:
+## Skip the merge train and merge immediately
 
-![Merge train position indicator](img/merge_train_position_v12_0.png)
+If you have a high-priority merge request, like a critical patch that must
+be merged urgently, select **Merge Immediately**.
 
-## Immediately merge a merge request with a merge train
+When you merge a merge request immediately:
 
-If you have a high-priority merge request (for example, a critical patch) that must
-be merged urgently, you can bypass the merge train by using the **Merge Immediately** option.
-This is the fastest option to get the change merged into the target branch.
-
-![Merge Immediately](img/merge_train_immediate_merge_v12_6.png)
+- The current merge train is recreated.
+- All pipelines restart.
+- Redundant pipelines [are cancelled](#automatic-pipeline-cancellation).
 
 WARNING:
-Each time you merge a merge request immediately, the current merge train is recreated,
-all pipelines restart, and [redundant pipelines are cancelled](#automatic-pipeline-cancellation).
+Merging immediately can use a lot of CI/CD resources. Use this option
+only in critical situations.
 
-### Automatic pipeline cancellation
+## Disable merge trains in GitLab 13.5 and earlier **(PREMIUM SELF)**
 
-> [Introduced](https://gitlab.com/gitlab-org/gitlab/-/issues/12996) in GitLab 12.3.
+In [GitLab 13.6 and later](https://gitlab.com/gitlab-org/gitlab/-/issues/244831),
+you can [enable or disable merge trains in the project settings](#enable-merge-trains).
 
-GitLab CI/CD can detect the presence of redundant pipelines, and cancels them
-to conserve CI resources.
+In GitLab 13.5 and earlier, merge trains are automatically enabled when
+[merged results pipelines](merged_results_pipelines.md) are enabled.
+To use merged results pipelines but not merge trains, enable the `disable_merge_trains`
+[feature flag](../../user/feature_flags.md).
 
-When a user merges a merge request immediately in an ongoing merge
-train, the train is reconstructed, because it recreates the expected
-post-merge commit and pipeline. In this case, the merge train may already
-have pipelines running against the previous expected post-merge commit.
-These pipelines are considered redundant and are automatically
-canceled.
+[GitLab administrators with access to the GitLab Rails console](../../administration/feature_flags.md)
+can enable the feature flag to disable merge trains:
 
-## Troubleshooting
+```ruby
+Feature.enable(:disable_merge_trains)
+```
 
-### Merge request dropped from the merge train immediately
+After you enable this feature flag, GitLab cancels existing merge trains and removes
+the **Start/Add to merge train** option from merge requests.
 
-If a merge request is not mergeable (for example, it's a draft merge request or it has a merge
-conflict), the merge train drops your merge request automatically.
+To disable the feature flag, which enables merge trains again:
 
-In these cases, the reason for dropping the merge request is in the **system notes**.
+```ruby
+Feature.disable(:disable_merge_trains)
+```
 
-To check the reason:
+## Troubleshooting
 
-1. Open the merge request that was dropped from the merge train.
-1. Select the **Discussion** tab.
-1. Find a system note that includes either:
-   - **... removed this merge request from the merge train because ...**
-   - **... aborted this merge request from the merge train because ...**
+### Merge request dropped from the merge train
 
-The reason is given in the text after the **because ...** phrase.
+If a merge request becomes unmergeable while a merge train pipeline is running,
+the merge train drops your merge request automatically. For example, this could be caused by:
 
-![Merge train failure](img/merge_train_failure.png)
+- Changing the merge request to a [draft](../../user/project/merge_requests/drafts.md).
+- A merge conflict.
+- A new conversation thread that is unresolved, when [all threads must be resolved](../../user/discussions/index.md#prevent-merge-unless-all-threads-are-resolved)
+  is enabled.
 
-### Merge When Pipeline Succeeds cannot be chosen
+You can find reason the merge request was dropped from the merge train in the system
+notes. Check the **Activity** section in the **Overview** tab for a message similar to:
+`User removed this merge request from the merge train because ...`
 
-[Merge When Pipeline Succeeds](../../user/project/merge_requests/merge_when_pipeline_succeeds.md)
-is currently unavailable when merge trains are enabled.
+### Cannot use merge when pipeline succeeds
 
-See [the related issue](https://gitlab.com/gitlab-org/gitlab/-/issues/12267)
+You cannot use [merge when pipeline succeeds](../../user/project/merge_requests/merge_when_pipeline_succeeds.md)
+when merge trains are enabled. See [the related issue](https://gitlab.com/gitlab-org/gitlab/-/issues/12267)
 for more information.
 
-### Merge train pipeline cannot be retried
+### Cannot retry merge train pipeline cannot
 
 When a merge train pipeline fails, the merge request is dropped from the train and the pipeline can't be retried.
 Merge train pipelines run on the merged result of the changes in the merge request and
-the changes from other merge requests already on the train. If the merge request is dropped from the train,
+changes from other merge requests already on the train. If the merge request is dropped from the train,
 the merged result is out of date and the pipeline can't be retried.
 
-Instead, you should [add the merge request to the train](#add-a-merge-request-to-a-merge-train)
-again, which triggers a new pipeline.
-
-If a job only fails intermittently, you can try using the [`retry`](../yaml/index.md#retry)
-keyword in the `.gitlab-ci.yml` file to have the job retried before the pipeline completes.
-If it succeeds after a retry, the merge request is not removed from the merge train.
+You can:
 
-### Unable to add to merge train with message "The pipeline for this merge request failed."
+- [Add the merge request to the train](#add-a-merge-request-to-a-merge-train) again,
+  which triggers a new pipeline.
+- Add the [`retry`](../yaml/index.md#retry) keyword to the job if it fails intermittently.
+  If it succeeds after a retry, the merge request is not removed from the merge train.
 
-Sometimes the **Start/Add to merge train** button is not available and the merge request says,
-"The pipeline for this merge request failed. Please retry the job or push a new commit to fix the failure."
+### Unable to add to the merge train
 
-This issue occurs when [**Pipelines must succeed**](../../user/project/merge_requests/merge_when_pipeline_succeeds.md#require-a-successful-pipeline-for-merge)
-is enabled in **Settings > General > Merge requests**. This option requires that you
-run a new successful pipeline before you can re-add a merge request to a merge train.
+When [**Pipelines must succeed**](../../user/project/merge_requests/merge_when_pipeline_succeeds.md#require-a-successful-pipeline-for-merge)
+is enabled, but the latest pipeline failed:
 
-Merge trains ensure that each pipeline has succeeded before a merge happens, so
-you can:
+- The **Start/Add to merge train** option is not available.
+- The merge request displays `The pipeline for this merge request failed. Please retry the job or push a new commit to fix the failure.`
 
-- Clear the **Pipelines must succeed** checkbox.
-- Select the **Enable merged results pipelines** and **Enable merge trains** checkboxes.
+Before you can re-add a merge request to a merge train, you can try to:
 
-  In GitLab 13.5 and earlier, there is only one checkbox, named
-  **Enable merge trains and pipelines for merged results**.
-
-If you want to keep the **Pipelines must succeed** option selected along with merge
-trains, create a new merged results pipeline when this error occurs:
-
-1. On the **Pipelines** tab, select **Run pipeline**.
-1. Select **Start/Add to merge train when pipeline succeeds**.
+- Retry the failed job. If it passes, and no other jobs failed, the pipeline is marked as successful.
+- Rerun the whole pipeline. On the **Pipelines** tab, select **Run pipeline**.
+- Push a new commit that fixes the issue, which also triggers a new pipeline.
 
 See [the related issue](https://gitlab.com/gitlab-org/gitlab/-/issues/35135)
 for more information.
-
-### Merge trains feature flag **(PREMIUM SELF)**
-
-In [GitLab 13.6 and later](https://gitlab.com/gitlab-org/gitlab/-/issues/244831),
-you can [enable or disable merge trains in the project settings](#enable-merge-trains).
-
-In GitLab 13.5 and earlier, merge trains are automatically enabled when
-[merged results pipelines](merged_results_pipelines.md) are enabled.
-To use merged results pipelines without using merge trains, you can enable a
-[feature flag](../../user/feature_flags.md) that blocks the merge trains feature.
-
-[GitLab administrators with access to the GitLab Rails console](../../administration/feature_flags.md)
-can enable the feature flag to disable merge trains:
-
-```ruby
-Feature.enable(:disable_merge_trains)
-```
-
-After you enable this feature flag, all existing merge trains are cancelled and
-the **Start/Add to merge train** button no longer appears in merge requests.
-
-To disable the feature flag, and enable merge trains again:
-
-```ruby
-Feature.disable(:disable_merge_trains)
-```
diff --git a/glfm_specification/output_example_snapshots/html.yml b/glfm_specification/output_example_snapshots/html.yml
index ef2ba39f925..69cff67d27d 100644
--- a/glfm_specification/output_example_snapshots/html.yml
+++ b/glfm_specification/output_example_snapshots/html.yml
@@ -1978,19 +1978,8 @@
     }
     ]]>
     <p>okay</p>
-  static: |-
-    &lt;![CDATA[
-    function matchwo(a,b)
-    {
-      if (a &lt; b &amp;&amp; a &lt; 0) then {
-        return 1;
-
-      } else {
+  static: |2-
 
-        return 0;
-      }
-    }
-    ]]&gt;
     <p data-sourcepos="13:1-13:4" dir="auto">okay</p>
   wysiwyg: |-
     <p>okay</p>
@@ -7424,14 +7413,14 @@
   canonical: |
     <p>foo <!ELEMENT br EMPTY></p>
   static: |-
-    <p data-sourcepos="1:1-1:23" dir="auto">foo &lt;!ELEMENT br EMPTY&gt;</p>
+    <p data-sourcepos="1:1-1:23" dir="auto">foo </p>
   wysiwyg: |-
     <p>foo </p>
 06_11_00__inlines__raw_html__018:
   canonical: |
     <p>foo <![CDATA[>&<]]></p>
   static: |-
-    <p data-sourcepos="1:1-1:19" dir="auto">foo &lt;![CDATA[&gt;&amp;&lt;]]&gt;</p>
+    <p data-sourcepos="1:1-1:19" dir="auto">foo &amp;&lt;]]&gt;</p>
   wysiwyg: |-
     <p>foo &amp;&lt;]]&gt;</p>
 06_11_00__inlines__raw_html__019:
diff --git a/lib/api/api.rb b/lib/api/api.rb
index 7a3631b2036..9d3e568074a 100644
--- a/lib/api/api.rb
+++ b/lib/api/api.rb
@@ -173,6 +173,7 @@ module API
         mount ::API::Appearance
         mount ::API::Deployments
         mount ::API::Metadata
+        mount ::API::MergeRequestDiffs
         mount ::API::UserCounts
         mount ::API::ProjectRepositoryStorageMoves
         mount ::API::SnippetRepositoryStorageMoves
@@ -260,7 +261,6 @@ module API
       mount ::API::MavenPackages
       mount ::API::Members
       mount ::API::MergeRequestApprovals
-      mount ::API::MergeRequestDiffs
       mount ::API::MergeRequests
       mount ::API::Metrics::Dashboard::Annotations
       mount ::API::Metrics::UserStarredDashboards
diff --git a/lib/api/merge_request_diffs.rb b/lib/api/merge_request_diffs.rb
index 87623568a04..26841bf6644 100644
--- a/lib/api/merge_request_diffs.rb
+++ b/lib/api/merge_request_diffs.rb
@@ -10,16 +10,18 @@ module API
     feature_category :code_review
 
     params do
-      requires :id, type: String, desc: 'The ID of a project'
+      requires :id, type: String, desc: 'The ID of the project'
     end
     resource :projects, requirements: API::NAMESPACE_OR_PROJECT_REQUIREMENTS do
       desc 'Get a list of merge request diff versions' do
         detail 'This feature was introduced in GitLab 8.12.'
         success Entities::MergeRequestDiff
+        tags %w[merge_requests]
+        is_array true
       end
 
       params do
-        requires :merge_request_iid, type: Integer, desc: 'The IID of a merge request'
+        requires :merge_request_iid, type: Integer, desc: 'The internal ID of the merge request'
         use :pagination
       end
       get ":id/merge_requests/:merge_request_iid/versions" do
@@ -31,11 +33,12 @@ module API
       desc 'Get a single merge request diff version' do
         detail 'This feature was introduced in GitLab 8.12.'
         success Entities::MergeRequestDiffFull
+        tags %w[merge_requests]
       end
 
       params do
-        requires :merge_request_iid, type: Integer, desc: 'The IID of a merge request'
-        requires :version_id, type: Integer, desc: 'The ID of a merge request diff version'
+        requires :merge_request_iid, type: Integer, desc: 'The internal ID of the merge request'
+        requires :version_id, type: Integer, desc: 'The ID of the merge request diff version'
       end
 
       get ":id/merge_requests/:merge_request_iid/versions/:version_id", urgency: :low do
diff --git a/lib/gitlab/sidekiq_middleware/duplicate_jobs/cookie.rb b/lib/gitlab/sidekiq_middleware/duplicate_jobs/cookie.rb
deleted file mode 100644
index 367ad4274a4..00000000000
--- a/lib/gitlab/sidekiq_middleware/duplicate_jobs/cookie.rb
+++ /dev/null
@@ -1,62 +0,0 @@
-# frozen_string_literal: true
-
-module Gitlab
-  module SidekiqMiddleware
-    module DuplicateJobs
-      # Cookie is a serialization format we use to minimize the number of keys
-      # we read, write and delete in Redis. Keys and values must be strings.
-      # Newlines are not allowed in either keys or values. Keys cannot contain
-      # '='. This format has the useful property that serialize(h1) +
-      # serialize(h2) == h1.merge(h2).
-      class Cookie
-        def self.serialize(hash)
-          hash.map { |k, v| "#{k}=#{v}\n" }.join
-        end
-
-        def self.deserialize(string)
-          string.each_line(chomp: true).to_h { |line| line.split('=', 2) }
-        end
-
-        def initialize(key)
-          @key = key
-        end
-
-        def set(hash, expiry)
-          with_redis { |redis| redis.set(@key, self.class.serialize(hash), nx: true, ex: expiry) }
-        end
-
-        def get
-          with_redis { |redis| self.class.deserialize(redis.get(@key) || '') }
-        end
-
-        def del
-          with_redis { |redis| redis.del(@key) }
-        end
-
-        def append(hash)
-          with_redis do |redis|
-            redis.eval(
-              # Only append if the keys exists. This way we are not responsible for
-              # setting the expiry of the key: that is the responsibility of #set.
-              'if redis.call("exists", KEYS[1]) > 0 then redis.call("append", KEYS[1], ARGV[1]) end',
-              keys: [@key],
-              argv: [self.class.serialize(hash)]
-            )
-          end
-        end
-
-        def with_redis(&block)
-          if Feature.enabled?(:use_primary_and_secondary_stores_for_duplicate_jobs) ||
-              Feature.enabled?(:use_primary_store_as_default_for_duplicate_jobs)
-            # TODO: Swap for Gitlab::Redis::SharedState after store transition
-            # https://gitlab.com/gitlab-com/gl-infra/scalability/-/issues/923
-            Gitlab::Redis::DuplicateJobs.with(&block) # rubocop:disable CodeReuse/ActiveRecord
-          else
-            # Keep the old behavior intact if neither feature flag is turned on
-            Sidekiq.redis(&block) # rubocop:disable Cop/SidekiqRedisCall
-          end
-        end
-      end
-    end
-  end
-end
diff --git a/lib/gitlab/sidekiq_middleware/duplicate_jobs/duplicate_job.rb b/lib/gitlab/sidekiq_middleware/duplicate_jobs/duplicate_job.rb
index a0eee0a150c..f452abe8d13 100644
--- a/lib/gitlab/sidekiq_middleware/duplicate_jobs/duplicate_job.rb
+++ b/lib/gitlab/sidekiq_middleware/duplicate_jobs/duplicate_job.rb
@@ -81,7 +81,7 @@ module Gitlab
 
           strong_memoize(:latest_wal_locations) do
             if Feature.enabled?(:duplicate_jobs_cookie)
-              latest_wal_locations_cookie
+              get_cookie.fetch('wal_locations', {})
             else
               latest_wal_locations_multi
             end
@@ -90,7 +90,7 @@ module Gitlab
 
         def delete!
           if Feature.enabled?(:duplicate_jobs_cookie)
-            cookie.del
+            with_redis { |redis| redis.del(cookie_key) }
           else
             Gitlab::Instrumentation::RedisClusterValidator.allow_cross_slot_commands do
               with_redis do |redis|
@@ -123,7 +123,7 @@ module Gitlab
           return unless reschedulable?
 
           if Feature.enabled?(:duplicate_jobs_cookie)
-            cookie.append({ 'deduplicated' => '1' })
+            with_redis { |redis| redis.eval(DEDUPLICATED_SCRIPT, keys: [cookie_key]) }
           else
             with_redis do |redis|
               redis.set(deduplicated_flag_key, DEDUPLICATED_FLAG_VALUE, ex: expiry, nx: true)
@@ -131,11 +131,21 @@ module Gitlab
           end
         end
 
+        DEDUPLICATED_SCRIPT = <<~LUA
+          local cookie_msgpack = redis.call("get", KEYS[1])
+          if not cookie_msgpack then
+            return
+          end
+          local cookie = cmsgpack.unpack(cookie_msgpack)
+          cookie.deduplicated = "1"
+          redis.call("set", KEYS[1], cmsgpack.pack(cookie), "ex", redis.call("ttl", KEYS[1]))
+        LUA
+
         def should_reschedule?
           return false unless reschedulable?
 
           if Feature.enabled?(:duplicate_jobs_cookie)
-            cookie.get['deduplicated'].present?
+            get_cookie['deduplicated'].present?
           else
             with_redis do |redis|
               redis.get(deduplicated_flag_key).present?
@@ -172,16 +182,26 @@ module Gitlab
         attr_writer :existing_jid
 
         def check_cookie!(expiry)
-          my_cookie = { 'jid' => jid }
-          job_wal_locations.each do |connection_name, location|
-            my_cookie["existing_wal_location:#{connection_name}"] = location
+          my_cookie = {
+            'jid' => jid,
+            'offsets' => {},
+            'wal_locations' => {},
+            'existing_wal_locations' => job_wal_locations
+          }
+
+          # There are 3 possible scenarios. In order of decreasing likelyhood:
+          # 1. SET NX succeeds.
+          # 2. SET NX fails, GET succeeds.
+          # 3. SET NX fails, the key expires and GET fails. In this case we must retry.
+          actual_cookie = {}
+          while actual_cookie.empty?
+            set_succeeded = with_redis { |r| r.set(cookie_key, my_cookie.to_msgpack, nx: true, ex: expiry) }
+            actual_cookie = set_succeeded ? my_cookie : get_cookie
           end
 
-          actual_cookie = cookie.set(my_cookie, expiry) ? my_cookie : cookie.get
-
           job['idempotency_key'] = idempotency_key
 
-          self.existing_wal_locations = filter_prefix(actual_cookie, 'existing_wal_location:')
+          self.existing_wal_locations = actual_cookie['existing_wal_locations']
           self.existing_jid = actual_cookie['jid']
         end
 
@@ -205,15 +225,40 @@ module Gitlab
         end
 
         def update_latest_wal_location_cookie!
-          new_wal_locations = {}
+          argv = []
           job_wal_locations.each do |connection_name, location|
-            offset = pg_wal_lsn_diff(connection_name).to_i
-            new_wal_locations["wal_location:#{connection_name}:#{offset}"] = location
+            argv += [connection_name, pg_wal_lsn_diff(connection_name), location]
           end
 
-          cookie.append(new_wal_locations)
+          with_redis { |r| r.eval(UPDATE_WAL_COOKIE_SCRIPT, keys: [cookie_key], argv: argv) }
         end
 
+        # Generally speaking, updating a Redis key by deserializing and
+        # serializing it on the Redis server is bad for performance. However in
+        # the case of DuplicateJobs we know that key updates are rare, and the
+        # most common operations are setting, getting and deleting the key. The
+        # aim of this design is to make the common operations as fast as
+        # possible.
+        UPDATE_WAL_COOKIE_SCRIPT = <<~LUA
+          local cookie_msgpack = redis.call("get", KEYS[1])
+          if not cookie_msgpack then
+            return
+          end
+          local cookie = cmsgpack.unpack(cookie_msgpack)
+
+          for i = 1, #ARGV, 3 do
+            local connection = ARGV[i]
+            local current_offset = cookie.offsets[connection]
+            local new_offset = tonumber(ARGV[i+1])
+            if not current_offset or current_offset < new_offset then
+              cookie.offsets[connection] = new_offset
+              cookie.wal_locations[connection] = ARGV[i+2]
+            end
+          end
+
+          redis.call("set", KEYS[1], cmsgpack.pack(cookie), "ex", redis.call("ttl", KEYS[1]))
+        LUA
+
         def update_latest_wal_location_multi!
           with_redis do |redis|
             redis.multi do |multi|
@@ -228,21 +273,6 @@ module Gitlab
           end
         end
 
-        def latest_wal_locations_cookie
-          wal_locations = {}
-          offsets = {}
-          filter_prefix(cookie.get, 'wal_location:').each do |key, value|
-            connection, offset = key.split(':', 2)
-            offset = offset.to_i
-            if !offsets[connection] || offsets[connection] < offset
-              offsets[connection] = offset
-              wal_locations[connection] = value
-            end
-          end
-
-          wal_locations
-        end
-
         def latest_wal_locations_multi
           read_wal_locations = {}
 
@@ -256,17 +286,6 @@ module Gitlab
           read_wal_locations.transform_values(&:value).compact
         end
 
-        # Filter_prefix extracts a sub-hash from a Ruby hash. For example, with
-        # input h = { 'foo:a' => '1', 'foo:b' => '2', 'bar' => '3' }, the output
-        # of filter_prefix(h, 'foo:') is { 'a' => '1', 'b' => '2' }.
-        def filter_prefix(hash, prefix)
-          out = {}
-          hash.each do |k, v|
-            out[k.delete_prefix(prefix)] = v if k.start_with?(prefix)
-          end
-          out
-        end
-
         def worker_klass
           @worker_klass ||= worker_class_name.to_s.safe_constantize
         end
@@ -331,8 +350,12 @@ module Gitlab
           "#{idempotency_key}:#{connection_name}:wal_location"
         end
 
-        def cookie
-          @cookie ||= Cookie.new("#{idempotency_key}:cookie")
+        def cookie_key
+          "#{idempotency_key}:cookie"
+        end
+
+        def get_cookie
+          with_redis { |redis| MessagePack.unpack(redis.get(cookie_key) || "\x80") }
         end
 
         def idempotency_key
diff --git a/locale/gitlab.pot b/locale/gitlab.pot
index a353ed4e544..41e6d115263 100644
--- a/locale/gitlab.pot
+++ b/locale/gitlab.pot
@@ -39364,9 +39364,15 @@ msgstr ""
 msgid "SuggestedReviewers|Get suggestions for reviewers based on GitLab's machine learning tool."
 msgstr ""
 
+msgid "SuggestedReviewers|Learn about suggested reviewers"
+msgstr ""
+
 msgid "SuggestedReviewers|Suggested reviewers"
 msgstr ""
 
+msgid "SuggestedReviewers|Suggested reviewers help link"
+msgstr ""
+
 msgid "SuggestedReviewers|Suggestions appear in the Reviewer section of the right sidebar"
 msgstr ""
 
diff --git a/spec/frontend/behaviors/markdown/render_sandboxed_mermaid_spec.js b/spec/frontend/behaviors/markdown/render_sandboxed_mermaid_spec.js
index 2b9442162aa..de0e5063e49 100644
--- a/spec/frontend/behaviors/markdown/render_sandboxed_mermaid_spec.js
+++ b/spec/frontend/behaviors/markdown/render_sandboxed_mermaid_spec.js
@@ -1,34 +1,127 @@
-import $ from 'jquery';
+import { createWrapper } from '@vue/test-utils';
+import { __ } from '~/locale';
 import { setHTMLFixture, resetHTMLFixture } from 'helpers/fixtures';
-import renderMermaid from '~/behaviors/markdown/render_sandboxed_mermaid';
+import renderMermaid, {
+  MAX_CHAR_LIMIT,
+  MAX_MERMAID_BLOCK_LIMIT,
+  LAZY_ALERT_SHOWN_CLASS,
+} from '~/behaviors/markdown/render_sandboxed_mermaid';
 
-describe('Render mermaid diagrams for Gitlab Flavoured Markdown', () => {
-  it('Does something', () => {
-    document.body.dataset.page = '';
-    setHTMLFixture(`
-      <div class="gl-relative markdown-code-block js-markdown-code">
-        <pre data-sourcepos="1:1-7:3" class="code highlight js-syntax-highlight language-mermaid white" lang="mermaid" id="code-4">
-          <code class="js-render-mermaid">
-            <span id="LC1" class="line" lang="mermaid">graph TD;</span>
-            <span id="LC2" class="line" lang="mermaid">A--&gt;B</span>
-            <span id="LC3" class="line" lang="mermaid">A--&gt;C</span>
-            <span id="LC4" class="line" lang="mermaid">B--&gt;D</span>
-            <span id="LC5" class="line" lang="mermaid">C--&gt;D</span>
-          </code>
-        </pre>
-        <copy-code>
-          <button type="button" class="btn btn-default btn-md gl-button btn-icon has-tooltip" data-title="Copy to clipboard" data-clipboard-target="pre#code-4">
-            <svg><use xlink:href="/assets/icons-7f1680a3670112fe4c8ef57b9dfb93f0f61b43a2a479d7abd6c83bcb724b9201.svg#copy-to-clipboard"></use></svg>
-          </button>
-        </copy-code>
-      </div>`);
-    const els = $('pre.js-syntax-highlight').find('.js-render-mermaid');
-
-    renderMermaid(els);
+describe('Mermaid diagrams renderer', () => {
+  // Finders
+  const findMermaidIframes = () => document.querySelectorAll('iframe[src="/-/sandbox/mermaid"]');
+  const findDangerousMermaidAlert = () =>
+    createWrapper(document.querySelector('[data-testid="alert-warning"]'));
 
+  // Helpers
+  const renderDiagrams = () => {
+    renderMermaid([...document.querySelectorAll('.js-render-mermaid')]);
     jest.runAllTimers();
-    expect(document.querySelector('pre.js-syntax-highlight').classList).toContain('gl-sr-only');
+  };
+
+  beforeEach(() => {
+    document.body.dataset.page = '';
+  });
 
+  afterEach(() => {
     resetHTMLFixture();
   });
+
+  it('renders a mermaid diagram', () => {
+    setHTMLFixture('<pre><code class="js-render-mermaid"></code></pre>');
+
+    expect(findMermaidIframes()).toHaveLength(0);
+
+    renderDiagrams();
+
+    expect(document.querySelector('pre').classList).toContain('gl-sr-only');
+    expect(findMermaidIframes()).toHaveLength(1);
+  });
+
+  describe('within a details element', () => {
+    beforeEach(() => {
+      setHTMLFixture('<details><pre><code class="js-render-mermaid"></code></pre></details>');
+      renderDiagrams();
+    });
+
+    it('does not render the diagram on load', () => {
+      expect(findMermaidIframes()).toHaveLength(0);
+    });
+
+    it('render the diagram when the details element is opened', () => {
+      document.querySelector('details').setAttribute('open', true);
+      document.querySelector('details').dispatchEvent(new Event('toggle'));
+      jest.runAllTimers();
+
+      expect(findMermaidIframes()).toHaveLength(1);
+    });
+  });
+
+  describe('dangerous diagrams', () => {
+    describe(`when the diagram's source exceeds ${MAX_CHAR_LIMIT} characters`, () => {
+      beforeEach(() => {
+        setHTMLFixture(
+          `<pre>
+            <code class="js-render-mermaid">${Array(MAX_CHAR_LIMIT + 1)
+              .fill('a')
+              .join('')}</code>
+          </pre>`,
+        );
+        renderDiagrams();
+      });
+      it('does not render the diagram on load', () => {
+        expect(findMermaidIframes()).toHaveLength(0);
+      });
+
+      it('shows a warning about performance impact when rendering the diagram', () => {
+        expect(document.querySelector('pre').classList).toContain(LAZY_ALERT_SHOWN_CLASS);
+        expect(findDangerousMermaidAlert().exists()).toBe(true);
+        expect(findDangerousMermaidAlert().text()).toContain(
+          __('Warning: Displaying this diagram might cause performance issues on this page.'),
+        );
+      });
+
+      it("renders the diagram when clicking on the alert's button", () => {
+        findDangerousMermaidAlert().find('button').trigger('click');
+        jest.runAllTimers();
+
+        expect(findMermaidIframes()).toHaveLength(1);
+      });
+    });
+
+    it(`stops rendering diagrams once the total rendered source exceeds ${MAX_CHAR_LIMIT} characters`, () => {
+      setHTMLFixture(
+        `<pre>
+          <code class="js-render-mermaid">${Array(MAX_CHAR_LIMIT - 1)
+            .fill('a')
+            .join('')}</code>
+          <code class="js-render-mermaid">2</code>
+          <code class="js-render-mermaid">3</code>
+          <code class="js-render-mermaid">4</code>
+        </pre>`,
+      );
+      renderDiagrams();
+
+      expect(findMermaidIframes()).toHaveLength(3);
+    });
+
+    // Note: The test case below is provided for convenience but should remain skipped as the DOM
+    // operations it requires are too expensive and would significantly slow down the test suite.
+    // eslint-disable-next-line jest/no-disabled-tests
+    it.skip(`stops rendering diagrams when the rendered diagrams count exceeds ${MAX_MERMAID_BLOCK_LIMIT}`, () => {
+      setHTMLFixture(
+        `<pre>
+          ${Array(MAX_MERMAID_BLOCK_LIMIT + 1)
+            .fill('<code class="js-render-mermaid"></code>')
+            .join('')}
+        </pre>`,
+      );
+      renderDiagrams();
+
+      expect([...document.querySelectorAll('.js-render-mermaid')]).toHaveLength(
+        MAX_MERMAID_BLOCK_LIMIT + 1,
+      );
+      expect(findMermaidIframes()).toHaveLength(MAX_MERMAID_BLOCK_LIMIT);
+    });
+  });
 });
diff --git a/spec/frontend/issues/list/components/issues_list_app_spec.js b/spec/frontend/issues/list/components/issues_list_app_spec.js
index 5133c02b190..16631752d6d 100644
--- a/spec/frontend/issues/list/components/issues_list_app_spec.js
+++ b/spec/frontend/issues/list/components/issues_list_app_spec.js
@@ -131,7 +131,6 @@ describe('CE IssuesListApp component', () => {
   const mountComponent = ({
     provide = {},
     data = {},
-    workItems = false,
     issuesQueryResponse = mockIssuesQueryResponse,
     issuesCountsQueryResponse = mockIssuesCountsQueryResponse,
     sortPreferenceMutationResponse = jest.fn().mockResolvedValue(setSortPreferenceMutationResponse),
@@ -150,9 +149,6 @@ describe('CE IssuesListApp component', () => {
       apolloProvider: createMockApollo(requestHandlers),
       router,
       provide: {
-        glFeatures: {
-          workItems,
-        },
         ...defaultProvide,
         ...provide,
       },
@@ -1060,45 +1056,23 @@ describe('CE IssuesListApp component', () => {
   });
 
   describe('fetching issues', () => {
-    describe('when work_items feature flag is disabled', () => {
-      beforeEach(() => {
-        wrapper = mountComponent({ workItems: false });
-        jest.runOnlyPendingTimers();
-      });
-
-      it('fetches issue, incident, and test case types', () => {
-        const types = [
-          WORK_ITEM_TYPE_ENUM_ISSUE,
-          WORK_ITEM_TYPE_ENUM_INCIDENT,
-          WORK_ITEM_TYPE_ENUM_TEST_CASE,
-        ];
-
-        expect(mockIssuesQueryResponse).toHaveBeenCalledWith(expect.objectContaining({ types }));
-        expect(mockIssuesCountsQueryResponse).toHaveBeenCalledWith(
-          expect.objectContaining({ types }),
-        );
-      });
+    beforeEach(() => {
+      wrapper = mountComponent();
+      jest.runOnlyPendingTimers();
     });
 
-    describe('when work_items feature flag is enabled', () => {
-      beforeEach(() => {
-        wrapper = mountComponent({ workItems: true });
-        jest.runOnlyPendingTimers();
-      });
-
-      it('fetches issue, incident, test case, and task types', () => {
-        const types = [
-          WORK_ITEM_TYPE_ENUM_ISSUE,
-          WORK_ITEM_TYPE_ENUM_INCIDENT,
-          WORK_ITEM_TYPE_ENUM_TEST_CASE,
-          WORK_ITEM_TYPE_ENUM_TASK,
-        ];
-
-        expect(mockIssuesQueryResponse).toHaveBeenCalledWith(expect.objectContaining({ types }));
-        expect(mockIssuesCountsQueryResponse).toHaveBeenCalledWith(
-          expect.objectContaining({ types }),
-        );
-      });
+    it('fetches issue, incident, test case, and task types', () => {
+      const types = [
+        WORK_ITEM_TYPE_ENUM_ISSUE,
+        WORK_ITEM_TYPE_ENUM_INCIDENT,
+        WORK_ITEM_TYPE_ENUM_TEST_CASE,
+        WORK_ITEM_TYPE_ENUM_TASK,
+      ];
+
+      expect(mockIssuesQueryResponse).toHaveBeenCalledWith(expect.objectContaining({ types }));
+      expect(mockIssuesCountsQueryResponse).toHaveBeenCalledWith(
+        expect.objectContaining({ types }),
+      );
     });
   });
 });
diff --git a/spec/frontend/notebook/cells/markdown_spec.js b/spec/frontend/notebook/cells/markdown_spec.js
index c757b55faf4..a7776bd5b69 100644
--- a/spec/frontend/notebook/cells/markdown_spec.js
+++ b/spec/frontend/notebook/cells/markdown_spec.js
@@ -5,20 +5,22 @@ import markdownTableJson from 'test_fixtures/blob/notebook/markdown-table.json';
 import basicJson from 'test_fixtures/blob/notebook/basic.json';
 import mathJson from 'test_fixtures/blob/notebook/math.json';
 import MarkdownComponent from '~/notebook/cells/markdown.vue';
+import Prompt from '~/notebook/cells/prompt.vue';
 
 const Component = Vue.extend(MarkdownComponent);
 
 window.katex = katex;
 
-function buildCellComponent(cell, relativePath = '') {
+function buildCellComponent(cell, relativePath = '', hidePrompt) {
   return mount(Component, {
     propsData: {
       cell,
+      hidePrompt,
     },
     provide: {
       relativeRawPath: relativePath,
     },
-  }).vm;
+  });
 }
 
 function buildMarkdownComponent(markdownContent, relativePath = '') {
@@ -33,7 +35,7 @@ function buildMarkdownComponent(markdownContent, relativePath = '') {
 }
 
 describe('Markdown component', () => {
-  let vm;
+  let wrapper;
   let cell;
   let json;
 
@@ -43,21 +45,30 @@ describe('Markdown component', () => {
     // eslint-disable-next-line prefer-destructuring
     cell = json.cells[1];
 
-    vm = buildCellComponent(cell);
+    wrapper = buildCellComponent(cell);
 
     await nextTick();
   });
 
-  it('does not render prompt', () => {
-    expect(vm.$el.querySelector('.prompt span')).toBeNull();
+  const findPrompt = () => wrapper.findComponent(Prompt);
+
+  it('renders a prompt by default', () => {
+    expect(findPrompt().exists()).toBe(true);
+  });
+
+  it('does not render a prompt if hidePrompt is true', () => {
+    wrapper = buildCellComponent(cell, '', true);
+    expect(findPrompt().exists()).toBe(false);
   });
 
   it('does not render the markdown text', () => {
-    expect(vm.$el.querySelector('.markdown').innerHTML.trim()).not.toEqual(cell.source.join(''));
+    expect(wrapper.vm.$el.querySelector('.markdown').innerHTML.trim()).not.toEqual(
+      cell.source.join(''),
+    );
   });
 
   it('renders the markdown HTML', () => {
-    expect(vm.$el.querySelector('.markdown h1')).not.toBeNull();
+    expect(wrapper.vm.$el.querySelector('.markdown h1')).not.toBeNull();
   });
 
   it('sanitizes Markdown output', async () => {
@@ -68,11 +79,11 @@ describe('Markdown component', () => {
     });
 
     await nextTick();
-    expect(vm.$el.querySelector('a').getAttribute('href')).toBeNull();
+    expect(wrapper.vm.$el.querySelector('a').getAttribute('href')).toBeNull();
   });
 
   it('sanitizes HTML', async () => {
-    const findLink = () => vm.$el.querySelector('.xss-link');
+    const findLink = () => wrapper.vm.$el.querySelector('.xss-link');
     Object.assign(cell, {
       source: ['<a href="test.js" data-remote=true data-type="script" class="xss-link">XSS</a>\n'],
     });
@@ -97,11 +108,11 @@ describe('Markdown component', () => {
       ["for embedded images, it doesn't", '![](data:image/jpeg;base64)\n', 'src="data:'],
       ["for images urls, it doesn't", '![](http://image.png)\n', 'src="http:'],
     ])('%s', async ([testMd, mustContain]) => {
-      vm = buildMarkdownComponent([testMd], '/raw/');
+      wrapper = buildMarkdownComponent([testMd], '/raw/');
 
       await nextTick();
 
-      expect(vm.$el.innerHTML).toContain(mustContain);
+      expect(wrapper.vm.$el.innerHTML).toContain(mustContain);
     });
   });
 
@@ -111,13 +122,13 @@ describe('Markdown component', () => {
     });
 
     it('renders images and text', async () => {
-      vm = buildCellComponent(json.cells[0]);
+      wrapper = buildCellComponent(json.cells[0]);
 
       await nextTick();
-      const images = vm.$el.querySelectorAll('img');
+      const images = wrapper.vm.$el.querySelectorAll('img');
       expect(images.length).toBe(5);
 
-      const columns = vm.$el.querySelectorAll('td');
+      const columns = wrapper.vm.$el.querySelectorAll('td');
       expect(columns.length).toBe(6);
 
       expect(columns[0].textContent).toEqual('Hello ');
@@ -141,81 +152,93 @@ describe('Markdown component', () => {
     });
 
     it('renders multi-line katex', async () => {
-      vm = buildCellComponent(json.cells[0]);
+      wrapper = buildCellComponent(json.cells[0]);
 
       await nextTick();
-      expect(vm.$el.querySelector('.katex')).not.toBeNull();
+      expect(wrapper.vm.$el.querySelector('.katex')).not.toBeNull();
     });
 
     it('renders inline katex', async () => {
-      vm = buildCellComponent(json.cells[1]);
+      wrapper = buildCellComponent(json.cells[1]);
 
       await nextTick();
-      expect(vm.$el.querySelector('p:first-child .katex')).not.toBeNull();
+      expect(wrapper.vm.$el.querySelector('p:first-child .katex')).not.toBeNull();
     });
 
     it('renders multiple inline katex', async () => {
-      vm = buildCellComponent(json.cells[1]);
+      wrapper = buildCellComponent(json.cells[1]);
 
       await nextTick();
-      expect(vm.$el.querySelectorAll('p:nth-child(2) .katex')).toHaveLength(4);
+      expect(wrapper.vm.$el.querySelectorAll('p:nth-child(2) .katex')).toHaveLength(4);
     });
 
     it('output cell in case of katex error', async () => {
-      vm = buildMarkdownComponent(['Some invalid $a & b$ inline formula $b & c$\n', '\n']);
+      wrapper = buildMarkdownComponent(['Some invalid $a & b$ inline formula $b & c$\n', '\n']);
 
       await nextTick();
       // expect one paragraph with no katex formula in it
-      expect(vm.$el.querySelectorAll('p')).toHaveLength(1);
-      expect(vm.$el.querySelectorAll('p .katex')).toHaveLength(0);
+      expect(wrapper.vm.$el.querySelectorAll('p')).toHaveLength(1);
+      expect(wrapper.vm.$el.querySelectorAll('p .katex')).toHaveLength(0);
     });
 
     it('output cell and render remaining formula in case of katex error', async () => {
-      vm = buildMarkdownComponent([
+      wrapper = buildMarkdownComponent([
         'An invalid $a & b$ inline formula and a vaild one $b = c$\n',
         '\n',
       ]);
 
       await nextTick();
       // expect one paragraph with no katex formula in it
-      expect(vm.$el.querySelectorAll('p')).toHaveLength(1);
-      expect(vm.$el.querySelectorAll('p .katex')).toHaveLength(1);
+      expect(wrapper.vm.$el.querySelectorAll('p')).toHaveLength(1);
+      expect(wrapper.vm.$el.querySelectorAll('p .katex')).toHaveLength(1);
     });
 
     it('renders math formula in list object', async () => {
-      vm = buildMarkdownComponent(["- list with inline $a=2$ inline formula $a' + b = c$\n", '\n']);
+      wrapper = buildMarkdownComponent([
+        "- list with inline $a=2$ inline formula $a' + b = c$\n",
+        '\n',
+      ]);
 
       await nextTick();
       // expect one list with a katex formula in it
-      expect(vm.$el.querySelectorAll('li')).toHaveLength(1);
-      expect(vm.$el.querySelectorAll('li .katex')).toHaveLength(2);
+      expect(wrapper.vm.$el.querySelectorAll('li')).toHaveLength(1);
+      expect(wrapper.vm.$el.querySelectorAll('li .katex')).toHaveLength(2);
     });
 
     it("renders math formula with tick ' in it", async () => {
-      vm = buildMarkdownComponent(["- list with inline $a=2$ inline formula $a' + b = c$\n", '\n']);
+      wrapper = buildMarkdownComponent([
+        "- list with inline $a=2$ inline formula $a' + b = c$\n",
+        '\n',
+      ]);
 
       await nextTick();
       // expect one list with a katex formula in it
-      expect(vm.$el.querySelectorAll('li')).toHaveLength(1);
-      expect(vm.$el.querySelectorAll('li .katex')).toHaveLength(2);
+      expect(wrapper.vm.$el.querySelectorAll('li')).toHaveLength(1);
+      expect(wrapper.vm.$el.querySelectorAll('li .katex')).toHaveLength(2);
     });
 
     it('renders math formula with less-than-operator < in it', async () => {
-      vm = buildMarkdownComponent(['- list with inline $a=2$ inline formula $a + b < c$\n', '\n']);
+      wrapper = buildMarkdownComponent([
+        '- list with inline $a=2$ inline formula $a + b < c$\n',
+        '\n',
+      ]);
 
       await nextTick();
       // expect one list with a katex formula in it
-      expect(vm.$el.querySelectorAll('li')).toHaveLength(1);
-      expect(vm.$el.querySelectorAll('li .katex')).toHaveLength(2);
+      expect(wrapper.vm.$el.querySelectorAll('li')).toHaveLength(1);
+      expect(wrapper.vm.$el.querySelectorAll('li .katex')).toHaveLength(2);
     });
 
     it('renders math formula with greater-than-operator > in it', async () => {
-      vm = buildMarkdownComponent(['- list with inline $a=2$ inline formula $a + b > c$\n', '\n']);
+      wrapper = buildMarkdownComponent([
+        '- list with inline $a=2$ inline formula $a + b > c$\n',
+        '\n',
+      ]);
 
       await nextTick();
       // expect one list with a katex formula in it
-      expect(vm.$el.querySelectorAll('li')).toHaveLength(1);
-      expect(vm.$el.querySelectorAll('li .katex')).toHaveLength(2);
+      expect(wrapper.vm.$el.querySelectorAll('li')).toHaveLength(1);
+      expect(wrapper.vm.$el.querySelectorAll('li .katex')).toHaveLength(2);
     });
   });
 });
diff --git a/spec/frontend/notebook/cells/output/index_spec.js b/spec/frontend/notebook/cells/output/index_spec.js
index 8bf049235a9..585cbb68eeb 100644
--- a/spec/frontend/notebook/cells/output/index_spec.js
+++ b/spec/frontend/notebook/cells/output/index_spec.js
@@ -1,12 +1,15 @@
 import { mount } from '@vue/test-utils';
 import json from 'test_fixtures/blob/notebook/basic.json';
 import Output from '~/notebook/cells/output/index.vue';
+import MarkdownOutput from '~/notebook/cells/output/markdown.vue';
+import { relativeRawPath, markdownCellContent } from '../../mock_data';
 
 describe('Output component', () => {
   let wrapper;
 
   const createComponent = (output) => {
     wrapper = mount(Output, {
+      provide: { relativeRawPath },
       propsData: {
         outputs: [].concat(output),
         count: 1,
@@ -95,6 +98,17 @@ describe('Output component', () => {
     });
   });
 
+  describe('Markdown output', () => {
+    beforeEach(() => {
+      const markdownType = { data: { 'text/markdown': markdownCellContent } };
+      createComponent(markdownType);
+    });
+
+    it('renders a markdown component', () => {
+      expect(wrapper.findComponent(MarkdownOutput).props('rawCode')).toBe(markdownCellContent);
+    });
+  });
+
   describe('default to plain text', () => {
     beforeEach(() => {
       const unknownType = json.cells[6];
diff --git a/spec/frontend/notebook/cells/output/markdown_spec.js b/spec/frontend/notebook/cells/output/markdown_spec.js
new file mode 100644
index 00000000000..e3490ed3bea
--- /dev/null
+++ b/spec/frontend/notebook/cells/output/markdown_spec.js
@@ -0,0 +1,44 @@
+import { mount } from '@vue/test-utils';
+import MarkdownOutput from '~/notebook/cells/output/markdown.vue';
+import Prompt from '~/notebook/cells/prompt.vue';
+import Markdown from '~/notebook/cells/markdown.vue';
+import { relativeRawPath, markdownCellContent } from '../../mock_data';
+
+describe('markdown output cell', () => {
+  let wrapper;
+
+  const createComponent = ({ count = 0, index = 0 } = {}) => {
+    wrapper = mount(MarkdownOutput, {
+      provide: { relativeRawPath },
+      propsData: {
+        rawCode: markdownCellContent,
+        count,
+        index,
+      },
+    });
+  };
+
+  beforeEach(() => {
+    createComponent();
+  });
+
+  const findPrompt = () => wrapper.findComponent(Prompt);
+  const findMarkdown = () => wrapper.findComponent(Markdown);
+
+  it.each`
+    index | count | showOutput
+    ${0}  | ${1}  | ${true}
+    ${1}  | ${2}  | ${false}
+    ${2}  | ${3}  | ${false}
+  `('renders a prompt', ({ index, count, showOutput }) => {
+    createComponent({ count, index });
+    expect(findPrompt().props()).toMatchObject({ count, showOutput, type: 'Out' });
+  });
+
+  it('renders a Markdown component', () => {
+    expect(findMarkdown().props()).toMatchObject({
+      cell: { source: markdownCellContent },
+      hidePrompt: true,
+    });
+  });
+});
diff --git a/spec/frontend/notebook/mock_data.js b/spec/frontend/notebook/mock_data.js
new file mode 100644
index 00000000000..b1419e1256f
--- /dev/null
+++ b/spec/frontend/notebook/mock_data.js
@@ -0,0 +1,2 @@
+export const relativeRawPath = '/test';
+export const markdownCellContent = ['# Test'];
diff --git a/spec/frontend/releases/components/asset_links_form_spec.js b/spec/frontend/releases/components/asset_links_form_spec.js
index 1ff5766b074..b1e9d8d1256 100644
--- a/spec/frontend/releases/components/asset_links_form_spec.js
+++ b/spec/frontend/releases/components/asset_links_form_spec.js
@@ -292,6 +292,42 @@ describe('Release edit component', () => {
     });
   });
 
+  describe('remove button state', () => {
+    describe('when there is only one link', () => {
+      beforeEach(() => {
+        factory({
+          release: {
+            ...release,
+            assets: {
+              links: release.assets.links.slice(0, 1),
+            },
+          },
+        });
+      });
+
+      it('remove asset link button should not be present', () => {
+        expect(wrapper.find('.remove-button').exists()).toBe(false);
+      });
+    });
+
+    describe('when there are multiple links', () => {
+      beforeEach(() => {
+        factory({
+          release: {
+            ...release,
+            assets: {
+              links: release.assets.links.slice(0, 2),
+            },
+          },
+        });
+      });
+
+      it('remove asset link button should be visible', () => {
+        expect(wrapper.find('.remove-button').exists()).toBe(true);
+      });
+    });
+  });
+
   describe('empty state', () => {
     describe('when the release fetched from the API has no links', () => {
       beforeEach(() => {
@@ -325,12 +361,6 @@ describe('Release edit component', () => {
       it('does not call the addEmptyAssetLink store method when the component is created', () => {
         expect(actions.addEmptyAssetLink).not.toHaveBeenCalled();
       });
-
-      it('calls addEmptyAssetLink when the final link is deleted by the user', () => {
-        wrapper.find('.remove-button').vm.$emit('click');
-
-        expect(actions.addEmptyAssetLink).toHaveBeenCalledTimes(1);
-      });
     });
   });
 });
diff --git a/spec/graphql/graphql_triggers_spec.rb b/spec/graphql/graphql_triggers_spec.rb
index a4a643582f5..a54cb8a7988 100644
--- a/spec/graphql/graphql_triggers_spec.rb
+++ b/spec/graphql/graphql_triggers_spec.rb
@@ -3,76 +3,89 @@
 require 'spec_helper'
 
 RSpec.describe GraphqlTriggers do
+  let_it_be(:issuable, refind: true) { create(:work_item) }
+
   describe '.issuable_assignees_updated' do
-    it 'triggers the issuableAssigneesUpdated subscription' do
-      assignees = create_list(:user, 2)
-      issue = create(:issue, assignees: assignees)
+    let(:assignees) { create_list(:user, 2) }
 
+    before do
+      issuable.update!(assignees: assignees)
+    end
+
+    it 'triggers the issuableAssigneesUpdated subscription' do
       expect(GitlabSchema.subscriptions).to receive(:trigger).with(
         'issuableAssigneesUpdated',
-        { issuable_id: issue.to_gid },
-        issue
+        { issuable_id: issuable.to_gid },
+        issuable
       )
 
-      GraphqlTriggers.issuable_assignees_updated(issue)
+      GraphqlTriggers.issuable_assignees_updated(issuable)
     end
   end
 
   describe '.issuable_title_updated' do
     it 'triggers the issuableTitleUpdated subscription' do
-      work_item = create(:work_item)
-
       expect(GitlabSchema.subscriptions).to receive(:trigger).with(
         'issuableTitleUpdated',
-        { issuable_id: work_item.to_gid },
-        work_item
+        { issuable_id: issuable.to_gid },
+        issuable
       ).and_call_original
 
-      GraphqlTriggers.issuable_title_updated(work_item)
+      GraphqlTriggers.issuable_title_updated(issuable)
     end
   end
 
   describe '.issuable_description_updated' do
     it 'triggers the issuableDescriptionUpdated subscription' do
-      work_item = create(:work_item)
-
       expect(GitlabSchema.subscriptions).to receive(:trigger).with(
         'issuableDescriptionUpdated',
-        { issuable_id: work_item.to_gid },
-        work_item
+        { issuable_id: issuable.to_gid },
+        issuable
       ).and_call_original
 
-      GraphqlTriggers.issuable_description_updated(work_item)
+      GraphqlTriggers.issuable_description_updated(issuable)
     end
   end
 
   describe '.issuable_labels_updated' do
-    it 'triggers the issuableLabelsUpdated subscription' do
-      project = create(:project)
-      labels = create_list(:label, 3, project: project)
-      issue = create(:issue, labels: labels)
+    let(:labels) { create_list(:label, 3, project: create(:project)) }
+
+    before do
+      issuable.update!(labels: labels)
+    end
 
+    it 'triggers the issuableLabelsUpdated subscription' do
       expect(GitlabSchema.subscriptions).to receive(:trigger).with(
         'issuableLabelsUpdated',
-        { issuable_id: issue.to_gid },
-        issue
+        { issuable_id: issuable.to_gid },
+        issuable
       )
 
-      GraphqlTriggers.issuable_labels_updated(issue)
+      GraphqlTriggers.issuable_labels_updated(issuable)
     end
   end
 
   describe '.issuable_dates_updated' do
     it 'triggers the issuableDatesUpdated subscription' do
-      work_item = create(:work_item)
-
       expect(GitlabSchema.subscriptions).to receive(:trigger).with(
         'issuableDatesUpdated',
-        { issuable_id: work_item.to_gid },
-        work_item
+        { issuable_id: issuable.to_gid },
+        issuable
+      ).and_call_original
+
+      GraphqlTriggers.issuable_dates_updated(issuable)
+    end
+  end
+
+  describe '.issuable_milestone_updated' do
+    it 'triggers the issuableMilestoneUpdated subscription' do
+      expect(GitlabSchema.subscriptions).to receive(:trigger).with(
+        'issuableMilestoneUpdated',
+        { issuable_id: issuable.to_gid },
+        issuable
       ).and_call_original
 
-      GraphqlTriggers.issuable_dates_updated(work_item)
+      GraphqlTriggers.issuable_milestone_updated(issuable)
     end
   end
 
diff --git a/spec/graphql/types/subscription_type_spec.rb b/spec/graphql/types/subscription_type_spec.rb
index c23a14deaf3..04f0c72b06f 100644
--- a/spec/graphql/types/subscription_type_spec.rb
+++ b/spec/graphql/types/subscription_type_spec.rb
@@ -11,6 +11,7 @@ RSpec.describe GitlabSchema.types['Subscription'] do
       issuable_description_updated
       issuable_labels_updated
       issuable_dates_updated
+      issuable_milestone_updated
       merge_request_reviewers_updated
       merge_request_merge_status_updated
     ]
diff --git a/spec/initializers/hashie_mash_permitted_patch_spec.rb b/spec/initializers/hashie_mash_permitted_patch_spec.rb
new file mode 100644
index 00000000000..0e9f8a485ff
--- /dev/null
+++ b/spec/initializers/hashie_mash_permitted_patch_spec.rb
@@ -0,0 +1,29 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe 'Hashie::Mash#permitted patch' do
+  let(:mash) { Hashie::Mash.new }
+
+  before do
+    load Rails.root.join('config/initializers/hashie_mash_permitted_patch.rb')
+  end
+
+  describe '#respond_to? with :permitted?' do
+    it 'returns false' do
+      expect(Gitlab::AppLogger).to receive(:info).with(
+        { message: 'Hashie::Mash#respond_to?(:permitted?)', caller: instance_of(Array) })
+
+      expect(mash.respond_to?(:permitted?)).to be false
+    end
+  end
+
+  describe '#permitted' do
+    it 'raises ArgumentError' do
+      expect(Gitlab::AppLogger).to receive(:info).with(
+        { message: 'Hashie::Mash#permitted?', caller: instance_of(Array) })
+
+      expect { mash.permitted? }.to raise_error(ArgumentError)
+    end
+  end
+end
diff --git a/spec/lib/gitlab/sidekiq_middleware/duplicate_jobs/cookie_spec.rb b/spec/lib/gitlab/sidekiq_middleware/duplicate_jobs/cookie_spec.rb
deleted file mode 100644
index 10e642b7713..00000000000
--- a/spec/lib/gitlab/sidekiq_middleware/duplicate_jobs/cookie_spec.rb
+++ /dev/null
@@ -1,130 +0,0 @@
-# frozen_string_literal: true
-
-require 'spec_helper'
-
-RSpec.describe Gitlab::SidekiqMiddleware::DuplicateJobs::Cookie, :clean_gitlab_redis_shared_state,
-:clean_gitlab_redis_queues do
-  describe 'serialization' do
-    it 'can round-trip a hash' do
-      h = { 'hello' => 'world', 'foo' => 'bar' }
-      expect(described_class.deserialize(described_class.serialize(h))).to eq(h)
-    end
-
-    it 'can merge by concatenating' do
-      h1 = { 'foo' => 'bar', 'baz' => 'qux' }
-      h2 = { 'foo' => 'other bar', 'hello' => 'world' }
-      concatenated = described_class.serialize(h1) + described_class.serialize(h2)
-      expect(described_class.deserialize(concatenated)).to eq(h1.merge(h2))
-    end
-  end
-
-  shared_examples 'with Redis persistence' do
-    let(:cookie) { described_class.new(key) }
-    let(:key) { 'redis_key' }
-    let(:hash) { { 'hello' => 'world' } }
-
-    describe '.set' do
-      subject { cookie.set(hash, expiry) }
-
-      let(:expiry) { 10 }
-
-      it 'stores the hash' do
-        expect(subject).to be_truthy
-        with_redis do |redis|
-          expect(redis.get(key)).to eq("hello=world\n")
-          expect(redis.ttl(key)).to be_within(1).of(expiry)
-        end
-      end
-
-      context 'when the key is set' do
-        before do
-          with_redis { |r| r.set(key, 'foobar') }
-        end
-
-        it 'does not overwrite existing keys' do
-          expect(subject).to be_falsey
-          with_redis do |redis|
-            expect(redis.get(key)).to eq('foobar')
-            expect(redis.ttl(key)).to eq(-1)
-          end
-        end
-      end
-    end
-
-    describe '.get' do
-      subject { cookie.get }
-
-      it { expect(subject).to eq({}) }
-
-      context 'when the key is set' do
-        before do
-          with_redis { |r| r.set(key, "hello=world\n") }
-        end
-
-        it { expect(subject).to eq({ 'hello' => 'world' }) }
-      end
-    end
-
-    describe '.append' do
-      subject { cookie.append(hash) }
-
-      it 'does not create the key' do
-        subject
-
-        with_redis do |redis|
-          expect(redis.get(key)).to eq(nil)
-        end
-      end
-
-      context 'when the key exists' do
-        before do
-          with_redis { |r| r.set(key, 'existing data', ex: 10) }
-        end
-
-        it 'appends without modifying ttl' do
-          subject
-
-          with_redis do |redis|
-            expect(redis.get(key)).to eq("existing datahello=world\n")
-            expect(redis.ttl(key)).to be_within(1).of(10)
-          end
-        end
-      end
-    end
-  end
-
-  context 'with multi-store feature flags turned on' do
-    def with_redis(&block)
-      Gitlab::Redis::DuplicateJobs.with(&block)
-    end
-
-    it 'use Gitlab::Redis::DuplicateJobs.with' do
-      expect(Gitlab::Redis::DuplicateJobs).to receive(:with).and_call_original
-      expect(Sidekiq).not_to receive(:redis)
-
-      described_class.new('hello').get
-    end
-
-    it_behaves_like 'with Redis persistence'
-  end
-
-  context 'when both multi-store feature flags are off' do
-    def with_redis(&block)
-      Sidekiq.redis(&block)
-    end
-
-    before do
-      stub_feature_flags(use_primary_and_secondary_stores_for_duplicate_jobs: false)
-      stub_feature_flags(use_primary_store_as_default_for_duplicate_jobs: false)
-    end
-
-    it 'use Sidekiq.redis' do
-      expect(Sidekiq).to receive(:redis).and_call_original
-      expect(Gitlab::Redis::DuplicateJobs).not_to receive(:with)
-
-      described_class.new('hello').get
-    end
-
-    it_behaves_like 'with Redis persistence'
-  end
-end
diff --git a/spec/lib/gitlab/sidekiq_middleware/duplicate_jobs/duplicate_job_spec.rb b/spec/lib/gitlab/sidekiq_middleware/duplicate_jobs/duplicate_job_spec.rb
index abe083f911b..1e8cb76905b 100644
--- a/spec/lib/gitlab/sidekiq_middleware/duplicate_jobs/duplicate_job_spec.rb
+++ b/spec/lib/gitlab/sidekiq_middleware/duplicate_jobs/duplicate_job_spec.rb
@@ -527,9 +527,8 @@ RSpec.describe Gitlab::SidekiqMiddleware::DuplicateJobs::DuplicateJob, :clean_gi
   end
 
   context 'with Redis cookies' do
-    let(:cookie_key) do
-      "#{idempotency_key}:cookie"
-    end
+    let(:cookie_key) { "#{idempotency_key}:cookie" }
+    let(:cookie) { get_redis_msgpack(cookie_key) }
 
     def with_redis(&block)
       Gitlab::Redis::DuplicateJobs.with(&block)
@@ -541,15 +540,16 @@ RSpec.describe Gitlab::SidekiqMiddleware::DuplicateJobs::DuplicateJob, :clean_gi
 
         shared_examples 'sets Redis keys with correct TTL' do
           it "adds an idempotency key with correct ttl" do
-            expected_cookie = <<~COOKIE
-              jid=123
-              existing_wal_location:main=#{wal_locations['main']}
-              existing_wal_location:ci=#{wal_locations['ci']}
-            COOKIE
-            expect { duplicate_job.check! }
-              .to change { read_idempotency_key_with_ttl(cookie_key) }
-                    .from([nil, -2])
-                    .to([expected_cookie, be_within(1).of(expected_ttl)])
+            expected_cookie = {
+              'jid' => '123',
+              'offsets' => {},
+              'wal_locations' => {},
+              'existing_wal_locations' => wal_locations
+            }
+
+            duplicate_job.check!
+            expect(cookie).to eq(expected_cookie)
+            expect(redis_ttl(cookie_key)).to be_within(1).of(expected_ttl)
           end
         end
 
@@ -576,15 +576,17 @@ RSpec.describe Gitlab::SidekiqMiddleware::DuplicateJobs::DuplicateJob, :clean_gi
 
       context 'when there was already a job with same arguments in the same queue' do
         before do
-          set_idempotency_key(cookie_key, "jid=existing-jid\n")
+          set_idempotency_key(cookie_key, existing_cookie.to_msgpack)
         end
 
+        let(:existing_cookie) { { 'jid' => 'existing-jid' } }
+
         it { expect(duplicate_job.check!).to eq('existing-jid') }
 
         it "does not change the existing key's TTL" do
           expect { duplicate_job.check! }
-            .not_to change { read_idempotency_key_with_ttl(cookie_key) }
-                  .from(["jid=existing-jid\n", -1])
+            .not_to change { redis_ttl(cookie_key) }
+                  .from(-1)
         end
 
         it 'sets the existing jid' do
@@ -601,20 +603,22 @@ RSpec.describe Gitlab::SidekiqMiddleware::DuplicateJobs::DuplicateJob, :clean_gi
           { main: ::ActiveRecord::Base,
             ci: ::ActiveRecord::Base })
 
-        set_idempotency_key(cookie_key, initial_cookie)
+        with_redis { |r| r.set(cookie_key, initial_cookie.to_msgpack, ex: expected_ttl) }
 
         # read existing_wal_locations
         duplicate_job.check!
       end
 
       let(:initial_cookie) do
-        <<~COOKIE
-          jid=foobar
-          existing_wal_location:main=0/D525E3A0
-          existing_wal_location:ci=AB/12340
-        COOKIE
+        {
+          'jid' => 'foobar',
+          'existing_wal_locations' => { 'main' => '0/D525E3A0', 'ci' => 'AB/12340' },
+          'offsets' => {},
+          'wal_locations' => {}
+        }
       end
 
+      let(:expected_ttl) { 123 }
       let(:new_wal) do
         {
           # offset is relative to `existing_wal`
@@ -626,34 +630,76 @@ RSpec.describe Gitlab::SidekiqMiddleware::DuplicateJobs::DuplicateJob, :clean_gi
       let(:wal_locations) { new_wal.transform_values { |v| v[:location] } }
 
       it 'stores a wal location to redis with an offset relative to existing wal location' do
-        expected_cookie = initial_cookie + <<~COOKIE
-          wal_location:main:#{new_wal['main'][:offset]}=#{new_wal['main'][:location]}
-          wal_location:ci:#{new_wal['ci'][:offset]}=#{new_wal['ci'][:location]}
-        COOKIE
+        duplicate_job.update_latest_wal_location!
+
+        expect(cookie['wal_locations']).to eq(wal_locations)
+        expect(cookie['offsets']).to eq(new_wal.transform_values { |v| v[:offset].to_i })
+        expect(redis_ttl(cookie_key)).to be_within(1).of(expected_ttl)
+      end
+    end
+
+    describe 'UPDATE_WAL_COOKIE_SCRIPT' do
+      subject do
+        with_redis do |redis|
+          redis.eval(described_class::UPDATE_WAL_COOKIE_SCRIPT, keys: [cookie_key], argv: argv)
+        end
+      end
+
+      let(:argv) { ['c1', 1, 'loc1', 'c2', 2, 'loc2', 'c3', 3, 'loc3'] }
+
+      it 'does not create the key' do
+        subject
+
+        expect(with_redis { |r| r.get(cookie_key) }).to eq(nil)
+      end
+
+      context 'when the key exists' do
+        let(:existing_cookie) { { 'offsets' => {}, 'wal_locations' => {} } }
+        let(:expected_ttl) { 123 }
+
+        before do
+          with_redis { |r| r.set(cookie_key, existing_cookie.to_msgpack, ex: expected_ttl) }
+        end
+
+        it 'updates all connections' do
+          subject
+
+          expect(cookie['wal_locations']).to eq({ 'c1' => 'loc1', 'c2' => 'loc2', 'c3' => 'loc3' })
+          expect(cookie['offsets']).to eq({ 'c1' => 1, 'c2' => 2, 'c3' => 3 })
+        end
+
+        it 'preserves the ttl' do
+          subject
+
+          expect(redis_ttl(cookie_key)).to be_within(1).of(expected_ttl)
+        end
 
-        expect { duplicate_job.update_latest_wal_location! }
-          .to change { read_idempotency_key_with_ttl(cookie_key) }
-                .from([initial_cookie, -1])
-                .to([expected_cookie, -1])
+        context 'and low offsets' do
+          let(:existing_cookie) do
+            {
+              'offsets' => { 'c1' => 0, 'c2' => 2 },
+              'wal_locations' => { 'c1' => 'loc1old', 'c2' => 'loc2old' }
+            }
+          end
+
+          it 'updates only some connections' do
+            subject
+
+            expect(cookie['wal_locations']).to eq({ 'c1' => 'loc1', 'c2' => 'loc2old', 'c3' => 'loc3' })
+            expect(cookie['offsets']).to eq({ 'c1' => 1, 'c2' => 2, 'c3' => 3 })
+          end
+        end
       end
     end
 
     describe '#latest_wal_locations' do
       context 'when job was deduplicated and wal locations were already persisted' do
         before do
-          cookie = <<~COOKIE
-            jid=foobar
-            wal_location:main:1=main1
-            wal_location:ci:2:=ci2
-            wal_location:main:5=main5
-            wal_location:ci:6=ci6
-            wal_location:main:3=main3
-            wal_location:ci:4=ci4
-          COOKIE
+          cookie = { 'wal_locations' => { 'main' => 'abc', 'ci' => 'def' } }.to_msgpack
           set_idempotency_key(cookie_key, cookie)
         end
 
-        it { expect(duplicate_job.latest_wal_locations).to eq({ 'main' => 'main5', 'ci' => 'ci6' }) }
+        it { expect(duplicate_job.latest_wal_locations).to eq({ 'main' => 'abc', 'ci' => 'def' }) }
       end
 
       context 'when job is not deduplication and wal locations were not persisted' do
@@ -668,30 +714,22 @@ RSpec.describe Gitlab::SidekiqMiddleware::DuplicateJobs::DuplicateJob, :clean_gi
 
       context 'when the key exists in redis' do
         before do
-          set_idempotency_key(cookie_key, "jid=existing-jid\n")
+          set_idempotency_key(cookie_key, "garbage")
         end
 
         shared_examples 'deleting the duplicate job' do
           shared_examples 'deleting keys from redis' do |key_name|
             it "removes the #{key_name} from redis" do
               expect { duplicate_job.delete! }
-                .to change { read_idempotency_key_with_ttl(key) }
-                      .from([from_value, -1])
-                      .to([nil, -2])
-            end
-          end
-
-          shared_examples 'does not delete key from redis' do |key_name|
-            it "does not remove the #{key_name} from redis" do
-              expect { duplicate_job.delete! }
-                .to not_change { read_idempotency_key_with_ttl(key) }
-                      .from([from_value, -1])
+                .to change { with_redis { |r| r.get(key) } }
+                      .from(from_value)
+                      .to(nil)
             end
           end
 
           it_behaves_like 'deleting keys from redis', 'cookie key' do
             let(:key) { cookie_key }
-            let(:from_value) { "jid=existing-jid\n" }
+            let(:from_value) { "garbage" }
           end
         end
 
@@ -730,8 +768,7 @@ RSpec.describe Gitlab::SidekiqMiddleware::DuplicateJobs::DuplicateJob, :clean_gi
         it 'sets the key in Redis' do
           duplicate_job.set_deduplicated_flag!
 
-          cookie = with_redis { |redis| redis.get(cookie_key) }
-          expect(cookie).to include("\ndeduplicated=1\n")
+          expect(cookie['deduplicated']).to eq('1')
         end
 
         it 'sets, gets and cleans up the deduplicated flag' do
@@ -754,9 +791,7 @@ RSpec.describe Gitlab::SidekiqMiddleware::DuplicateJobs::DuplicateJob, :clean_gi
           duplicate_job.check!
           duplicate_job.set_deduplicated_flag!
 
-          cookie = with_redis { |redis| redis.get(cookie_key) }
-
-          expect(cookie).not_to include('deduplicated=')
+          expect(cookie['deduplicated']).to eq(nil)
         end
 
         it 'does not set the deduplicated flag' do
@@ -783,7 +818,7 @@ RSpec.describe Gitlab::SidekiqMiddleware::DuplicateJobs::DuplicateJob, :clean_gi
       end
 
       it 'returns true if the existing jid is different from the job jid' do
-        set_idempotency_key(cookie_key, "jid=a different jid\n")
+        set_idempotency_key(cookie_key, { 'jid' => 'a different jid' }.to_msgpack)
         duplicate_job.check!
 
         expect(duplicate_job.duplicate?).to be(true)
@@ -794,13 +829,12 @@ RSpec.describe Gitlab::SidekiqMiddleware::DuplicateJobs::DuplicateJob, :clean_gi
       with_redis { |r| r.set(key, value) }
     end
 
-    def read_idempotency_key_with_ttl(key)
-      with_redis do |redis|
-        redis.pipelined do |p|
-          p.get(key)
-          p.ttl(key)
-        end
-      end
+    def get_redis_msgpack(key)
+      MessagePack.unpack(with_redis { |redis| redis.get(key) })
+    end
+
+    def redis_ttl(key)
+      with_redis { |redis| redis.ttl(key) }
     end
   end
 
diff --git a/spec/services/issues/update_service_spec.rb b/spec/services/issues/update_service_spec.rb
index 20b1a1f58bb..ebc870406e8 100644
--- a/spec/services/issues/update_service_spec.rb
+++ b/spec/services/issues/update_service_spec.rb
@@ -104,10 +104,33 @@ RSpec.describe Issues::UpdateService, :mailer do
         expect(issue.issue_customer_relations_contacts.last.contact).to eq contact
       end
 
-      it 'updates issue milestone when passing `milestone` param' do
-        update_issue(milestone: milestone)
+      context 'when updating milestone' do
+        before do
+          update_issue({ milestone: nil })
+        end
 
-        expect(issue.milestone).to eq milestone
+        it 'updates issue milestone when passing `milestone` param' do
+          expect { update_issue({ milestone: milestone }) }
+            .to change(issue, :milestone).to(milestone).from(nil)
+        end
+
+        it "triggers 'issuableMilestoneUpdated'" do
+          expect(GraphqlTriggers).to receive(:issuable_milestone_updated).with(issue).and_call_original
+
+          update_issue({ milestone: milestone })
+        end
+
+        context 'when milestone remains unchanged' do
+          before do
+            update_issue({ title: 'abc', milestone: milestone })
+          end
+
+          it "does not trigger 'issuableMilestoneUpdated'" do
+            expect(GraphqlTriggers).not_to receive(:issuable_milestone_updated)
+
+            update_issue({ milestone: milestone })
+          end
+        end
       end
 
       context 'when sentry identifier is given' do
diff --git a/spec/services/work_items/update_service_spec.rb b/spec/services/work_items/update_service_spec.rb
index 1761d1104dd..68efb4c220b 100644
--- a/spec/services/work_items/update_service_spec.rb
+++ b/spec/services/work_items/update_service_spec.rb
@@ -311,6 +311,34 @@ RSpec.describe WorkItems::UpdateService do
           end
         end
       end
+
+      context 'for milestone widget' do
+        let_it_be(:milestone) { create(:milestone, project: project) }
+
+        let(:widget_params) { { milestone_widget: { milestone_id: milestone.id } } }
+
+        context 'when milestone is updated' do
+          it "triggers 'issuableMilestoneUpdated'" do
+            expect(work_item.milestone).to eq(nil)
+            expect(GraphqlTriggers).to receive(:issuable_milestone_updated).with(work_item).and_call_original
+
+            update_work_item
+          end
+        end
+
+        context 'when milestone remains unchanged' do
+          before do
+            update_work_item
+          end
+
+          it "does not trigger 'issuableMilestoneUpdated'" do
+            expect(work_item.milestone).to eq(milestone)
+            expect(GraphqlTriggers).not_to receive(:issuable_milestone_updated)
+
+            update_work_item
+          end
+        end
+      end
     end
 
     describe 'label updates' do