21 files changed, 166 insertions, 16 deletions

diff --git a/app/controllers/projects/merge_requests/diffs_controller.rb b/app/controllers/projects/merge_requests/diffs_controller.rb
index 72e76f56540..872497992e1 100644
--- a/app/controllers/projects/merge_requests/diffs_controller.rb
+++ b/app/controllers/projects/merge_requests/diffs_controller.rb
@@ -111,6 +111,11 @@ class Projects::MergeRequests::DiffsController < Projects::MergeRequests::Applic
       end
     end
 
+    if Gitlab::Utils.to_boolean(params[:diff_head]) && @merge_request.diffable_merge_ref?
+      return CompareService.new(@project, @merge_request.merge_ref_head.sha)
+        .execute(@project, @merge_request.target_branch)
+    end
+
     if @start_sha
       @merge_request_diff.compare_with(@start_sha)
     else
diff --git a/app/models/concerns/issuable.rb b/app/models/concerns/issuable.rb
index f3e03ed22d7..78d815e5858 100644
--- a/app/models/concerns/issuable.rb
+++ b/app/models/concerns/issuable.rb
@@ -91,6 +91,7 @@ module Issuable
     validate :description_max_length_for_new_records_is_valid, on: :update
 
     before_validation :truncate_description_on_import!
+    after_save :store_mentions!, if: :any_mentionable_attributes_changed?
 
     scope :authored, ->(user) { where(author_id: user) }
     scope :recent, -> { reorder(id: :desc) }
diff --git a/app/models/concerns/mentionable.rb b/app/models/concerns/mentionable.rb
index b43b91699ab..d157404f7bc 100644
--- a/app/models/concerns/mentionable.rb
+++ b/app/models/concerns/mentionable.rb
@@ -99,18 +99,23 @@ module Mentionable
     # threw the `ActiveRecord::RecordNotUnique` exception in first place.
     self.class.safe_ensure_unique(retries: 1) do
       user_mention = model_user_mention
+
+      # this may happen due to notes polymorphism, so noteable_id may point to a record that no longer exists
+      # as we cannot have FK on noteable_id
+      break if user_mention.blank?
+
       user_mention.mentioned_users_ids = references[:mentioned_users_ids]
       user_mention.mentioned_groups_ids = references[:mentioned_groups_ids]
       user_mention.mentioned_projects_ids = references[:mentioned_projects_ids]
 
       if user_mention.has_mentions?
         user_mention.save!
-      elsif user_mention.persisted?
+      else
         user_mention.destroy!
       end
-
-      true
     end
+
+    true
   end
 
   def referenced_users
@@ -218,6 +223,12 @@ module Mentionable
     source.select { |key, val| mentionable.include?(key) }
   end
 
+  def any_mentionable_attributes_changed?
+    self.class.mentionable_attrs.any? do |attr|
+      saved_changes.key?(attr.first)
+    end
+  end
+
   # Determine whether or not a cross-reference Note has already been created between this Mentionable and
   # the specified target.
   def cross_reference_exists?(target)
diff --git a/app/models/deployment.rb b/app/models/deployment.rb
index 0c679a3075b..5450357fe1b 100644
--- a/app/models/deployment.rb
+++ b/app/models/deployment.rb
@@ -39,6 +39,7 @@ class Deployment < ApplicationRecord
   scope :for_status, -> (status) { where(status: status) }
 
   scope :visible, -> { where(status: %i[running success failed canceled]) }
+  scope :stoppable, -> { where.not(on_stop: nil).where.not(deployable_id: nil).success }
 
   state_machine :status, initial: :created do
     event :run do
diff --git a/app/models/environment.rb b/app/models/environment.rb
index 973f1243e6b..4635b05fcc7 100644
--- a/app/models/environment.rb
+++ b/app/models/environment.rb
@@ -61,6 +61,7 @@ class Environment < ApplicationRecord
   scope :in_review_folder, -> { where(environment_type: "review") }
   scope :for_name, -> (name) { where(name: name) }
   scope :preload_cluster, -> { preload(last_deployment: :cluster) }
+  scope :auto_stoppable, -> (limit) { available.where('auto_stop_at < ?', Time.zone.now).limit(limit) }
 
   ##
   # Search environments which have names like the given query.
@@ -107,6 +108,44 @@ class Environment < ApplicationRecord
     find_or_create_by(name: name)
   end
 
+  class << self
+    ##
+    # This method returns stop actions (jobs) for multiple environments within one
+    # query. It's useful to avoid N+1 problem.
+    #
+    # NOTE: The count of environments should be small~medium (e.g. < 5000)
+    def stop_actions
+      cte = cte_for_deployments_with_stop_action
+      ci_builds = Ci::Build.arel_table
+
+      inner_join_stop_actions = ci_builds.join(cte.table).on(
+        ci_builds[:project_id].eq(cte.table[:project_id])
+          .and(ci_builds[:ref].eq(cte.table[:ref]))
+          .and(ci_builds[:name].eq(cte.table[:on_stop]))
+      ).join_sources
+
+      pipeline_ids = ci_builds.join(cte.table).on(
+        ci_builds[:id].eq(cte.table[:deployable_id])
+      ).project(:commit_id)
+
+      Ci::Build.joins(inner_join_stop_actions)
+               .with(cte.to_arel)
+               .where(ci_builds[:commit_id].in(pipeline_ids))
+               .where(status: HasStatus::BLOCKED_STATUS)
+               .preload_project_and_pipeline_project
+               .preload(:user, :metadata, :deployment)
+    end
+
+    private
+
+    def cte_for_deployments_with_stop_action
+      Gitlab::SQL::CTE.new(:deployments_with_stop_action,
+        Deployment.where(environment_id: select(:id))
+          .distinct_on_environment
+          .stoppable)
+    end
+  end
+
   def clear_prometheus_reactive_cache!(query_name)
     cluster_prometheus_adapter&.clear_prometheus_reactive_cache!(query_name, self)
   end
diff --git a/app/models/issue.rb b/app/models/issue.rb
index 684108b1a7a..d01aa78a2c1 100644
--- a/app/models/issue.rb
+++ b/app/models/issue.rb
@@ -45,7 +45,7 @@ class Issue < ApplicationRecord
   has_many :issue_assignees
   has_many :assignees, class_name: "User", through: :issue_assignees
   has_many :zoom_meetings
-  has_many :user_mentions, class_name: "IssueUserMention"
+  has_many :user_mentions, class_name: "IssueUserMention", dependent: :delete_all # rubocop:disable Cop/ActiveRecordDependent
   has_one :sentry_issue
 
   accepts_nested_attributes_for :sentry_issue
diff --git a/app/models/merge_request.rb b/app/models/merge_request.rb
index b8f51b58fd3..14aa6ac066e 100644
--- a/app/models/merge_request.rb
+++ b/app/models/merge_request.rb
@@ -77,7 +77,7 @@ class MergeRequest < ApplicationRecord
 
   has_many :merge_request_assignees
   has_many :assignees, class_name: "User", through: :merge_request_assignees
-  has_many :user_mentions, class_name: "MergeRequestUserMention"
+  has_many :user_mentions, class_name: "MergeRequestUserMention", dependent: :delete_all # rubocop:disable Cop/ActiveRecordDependent
 
   has_many :deployment_merge_requests
 
@@ -840,6 +840,10 @@ class MergeRequest < ApplicationRecord
   end
   # rubocop: enable CodeReuse/ServiceClass
 
+  def diffable_merge_ref?
+    Feature.enabled?(:diff_compare_with_head, target_project) && can_be_merged? && merge_ref_head.present?
+  end
+
   # Returns boolean indicating the merge_status should be rechecked in order to
   # switch to either can_be_merged or cannot_be_merged.
   def recheck_merge_status?
diff --git a/app/models/note.rb b/app/models/note.rb
index 8af650e27aa..97e84bb79f6 100644
--- a/app/models/note.rb
+++ b/app/models/note.rb
@@ -157,6 +157,7 @@ class Note < ApplicationRecord
   after_save :expire_etag_cache, unless: :importing?
   after_save :touch_noteable, unless: :importing?
   after_destroy :expire_etag_cache
+  after_save :store_mentions!, if: :any_mentionable_attributes_changed?
 
   class << self
     def model_name
@@ -498,6 +499,8 @@ class Note < ApplicationRecord
   end
 
   def user_mentions
+    return Note.none unless noteable.present?
+
     noteable.user_mentions.where(note: self)
   end
 
@@ -506,6 +509,8 @@ class Note < ApplicationRecord
   # Using this method followed by a call to `save` may result in ActiveRecord::RecordNotUnique exception
   # in a multithreaded environment. Make sure to use it within a `safe_ensure_unique` block.
   def model_user_mention
+    return if user_mentions.is_a?(ActiveRecord::NullRelation)
+
     user_mentions.first_or_initialize
   end
 
diff --git a/app/models/snippet.rb b/app/models/snippet.rb
index e2b72dfde7a..4ba8e6a94e6 100644
--- a/app/models/snippet.rb
+++ b/app/models/snippet.rb
@@ -41,7 +41,7 @@ class Snippet < ApplicationRecord
   belongs_to :project
 
   has_many :notes, as: :noteable, dependent: :destroy # rubocop:disable Cop/ActiveRecordDependent
-  has_many :user_mentions, class_name: "SnippetUserMention"
+  has_many :user_mentions, class_name: "SnippetUserMention", dependent: :delete_all # rubocop:disable Cop/ActiveRecordDependent
   has_one :snippet_repository, inverse_of: :snippet
 
   delegate :name, :email, to: :author, prefix: true, allow_nil: true
@@ -66,6 +66,8 @@ class Snippet < ApplicationRecord
 
   validates :visibility_level, inclusion: { in: Gitlab::VisibilityLevel.values }
 
+  after_save :store_mentions!, if: :any_mentionable_attributes_changed?
+
   # Scopes
   scope :are_internal, -> { where(visibility_level: Snippet::INTERNAL) }
   scope :are_private, -> { where(visibility_level: Snippet::PRIVATE) }
diff --git a/app/serializers/merge_request_diff_entity.rb b/app/serializers/merge_request_diff_entity.rb
index 5c79b165ee9..aa0ac7d2a7e 100644
--- a/app/serializers/merge_request_diff_entity.rb
+++ b/app/serializers/merge_request_diff_entity.rb
@@ -34,6 +34,14 @@ class MergeRequestDiffEntity < Grape::Entity
     merge_request_version_path(project, merge_request, merge_request_diff)
   end
 
+  expose :head_version_path do |merge_request_diff|
+    project = merge_request.target_project
+
+    next unless project && merge_request.diffable_merge_ref?
+
+    diffs_project_merge_request_path(project, merge_request, diff_head: true)
+  end
+
   expose :version_path do |merge_request_diff|
     start_sha = options[:start_sha]
     project = merge_request.target_project
diff --git a/app/services/ci/stop_environments_service.rb b/app/services/ci/stop_environments_service.rb
index d9a800791f2..14ef744ada1 100644
--- a/app/services/ci/stop_environments_service.rb
+++ b/app/services/ci/stop_environments_service.rb
@@ -16,6 +16,22 @@ module Ci
       merge_request.environments.each { |environment| stop(environment) }
     end
 
+    ##
+    # This method is for stopping multiple environments in a batch style.
+    # The maximum acceptable count of environments is roughly 5000. Please
+    # apply acceptable `LIMIT` clause to the `environments` relation.
+    def self.execute_in_batch(environments)
+      stop_actions = environments.stop_actions.load
+
+      environments.update_all(auto_stop_at: nil, state: 'stopped')
+
+      stop_actions.each do |stop_action|
+        stop_action.play(stop_action.user)
+      rescue => e
+        Gitlab::ErrorTracking.track_error(e, deployable_id: stop_action.id)
+      end
+    end
+
     private
 
     def environments
diff --git a/app/services/environments/auto_stop_service.rb b/app/services/environments/auto_stop_service.rb
new file mode 100644
index 00000000000..6eef8138493
--- /dev/null
+++ b/app/services/environments/auto_stop_service.rb
@@ -0,0 +1,38 @@
+# frozen_string_literal: true
+
+module Environments
+  class AutoStopService
+    include ::Gitlab::ExclusiveLeaseHelpers
+    include ::Gitlab::LoopHelpers
+
+    BATCH_SIZE = 100
+    LOOP_TIMEOUT = 45.minutes
+    LOOP_LIMIT = 1000
+    EXCLUSIVE_LOCK_KEY = 'environments:auto_stop:lock'
+    LOCK_TIMEOUT = 50.minutes
+
+    ##
+    # Stop expired environments on GitLab instance
+    #
+    # This auto stop process cannot run for more than 45 minutes. This is for
+    # preventing multiple `AutoStopCronWorker` CRON jobs run concurrently,
+    # which is scheduled at every hour.
+    def execute
+      in_lock(EXCLUSIVE_LOCK_KEY, ttl: LOCK_TIMEOUT, retries: 1) do
+        loop_until(timeout: LOOP_TIMEOUT, limit: LOOP_LIMIT) do
+          stop_in_batch
+        end
+      end
+    end
+
+    private
+
+    def stop_in_batch
+      environments = Environment.auto_stoppable(BATCH_SIZE)
+
+      return false unless environments.exists? && Feature.enabled?(:auto_stop_environments)
+
+      Ci::StopEnvironmentsService.execute_in_batch(environments)
+    end
+  end
+end
diff --git a/app/services/issuable_base_service.rb b/app/services/issuable_base_service.rb
index b59bb803778..830afbf4a43 100644
--- a/app/services/issuable_base_service.rb
+++ b/app/services/issuable_base_service.rb
@@ -168,7 +168,7 @@ class IssuableBaseService < BaseService
     before_create(issuable)
 
     issuable_saved = issuable.with_transaction_returning_status do
-      issuable.save && issuable.store_mentions!
+      issuable.save
     end
 
     if issuable_saved
@@ -233,7 +233,7 @@ class IssuableBaseService < BaseService
       ensure_milestone_available(issuable)
 
       issuable_saved = issuable.with_transaction_returning_status do
-        issuable.save(touch: should_touch) && issuable.store_mentions!
+        issuable.save(touch: should_touch)
       end
 
       if issuable_saved
diff --git a/app/services/notes/create_service.rb b/app/services/notes/create_service.rb
index 50dc98b88e9..4a0d85038ee 100644
--- a/app/services/notes/create_service.rb
+++ b/app/services/notes/create_service.rb
@@ -2,7 +2,6 @@
 
 module Notes
   class CreateService < ::Notes::BaseService
-    # rubocop:disable Metrics/CyclomaticComplexity
     def execute
       note = Notes::BuildService.new(project, current_user, params.except(:merge_request_diff_head_sha)).execute
 
@@ -34,7 +33,7 @@ module Notes
       end
 
       note_saved = note.with_transaction_returning_status do
-        !only_commands && note.save && note.store_mentions!
+        !only_commands && note.save
       end
 
       if note_saved
@@ -67,7 +66,6 @@ module Notes
 
       note
     end
-    # rubocop:enable Metrics/CyclomaticComplexity
 
     private
 
diff --git a/app/services/notes/update_service.rb b/app/services/notes/update_service.rb
index c8b0dc30209..3070e7b0e53 100644
--- a/app/services/notes/update_service.rb
+++ b/app/services/notes/update_service.rb
@@ -10,7 +10,7 @@ module Notes
       note.assign_attributes(params.merge(updated_by: current_user))
 
       note.with_transaction_returning_status do
-        note.save && note.store_mentions!
+        note.save
       end
 
       only_commands = false
diff --git a/app/services/snippets/create_service.rb b/app/services/snippets/create_service.rb
index 250e99c466a..51860adca77 100644
--- a/app/services/snippets/create_service.rb
+++ b/app/services/snippets/create_service.rb
@@ -24,7 +24,7 @@ module Snippets
       spam_check(snippet, current_user)
 
       snippet_saved = snippet.with_transaction_returning_status do
-        snippet.save && snippet.store_mentions!
+        snippet.save
       end
 
       if snippet_saved
diff --git a/app/services/snippets/update_service.rb b/app/services/snippets/update_service.rb
index 8d2c8cac148..c0c0aec2050 100644
--- a/app/services/snippets/update_service.rb
+++ b/app/services/snippets/update_service.rb
@@ -21,7 +21,7 @@ module Snippets
       spam_check(snippet, current_user)
 
       snippet_saved = snippet.with_transaction_returning_status do
-        snippet.save && snippet.store_mentions!
+        snippet.save
       end
 
       if snippet_saved
diff --git a/app/views/clusters/clusters/gcp/_form.html.haml b/app/views/clusters/clusters/gcp/_form.html.haml
index 66da76d7a43..e83bf61ab9b 100644
--- a/app/views/clusters/clusters/gcp/_form.html.haml
+++ b/app/views/clusters/clusters/gcp/_form.html.haml
@@ -70,7 +70,7 @@
           label_class: 'label-bold' }
         .form-text.text-muted
           = s_('ClusterIntegration|Uses the Cloud Run, Istio, and HTTP Load Balancing addons for this cluster.')
-          = link_to _('More information'), help_page_path('user/project/clusters/index.md', anchor: 'cloud-run-on-gke'), target: '_blank'
+          = link_to _('More information'), help_page_path('user/project/clusters/add_remove_clusters.md', anchor: 'cloud-run-for-anthos'), target: '_blank'
 
   .form-group
     = field.check_box :managed, { label: s_('ClusterIntegration|GitLab-managed cluster'),
diff --git a/app/views/clusters/clusters/show.html.haml b/app/views/clusters/clusters/show.html.haml
index 59ce28d2d26..e1f011a3225 100644
--- a/app/views/clusters/clusters/show.html.haml
+++ b/app/views/clusters/clusters/show.html.haml
@@ -34,7 +34,7 @@
   environments_help_path: help_page_path('ci/environments', anchor: 'defining-environments'),
   clusters_help_path: help_page_path('user/project/clusters/index.md', anchor: 'deploying-to-a-kubernetes-cluster'),
   deploy_boards_help_path: help_page_path('user/project/deploy_boards.html', anchor: 'enabling-deploy-boards'),
-  cloud_run_help_path: help_page_path('user/project/clusters/index.md', anchor: 'cloud-run-on-gke'),
+  cloud_run_help_path: help_page_path('user/project/clusters/add_remove_clusters.md', anchor: 'cloud-run-for-anthos'),
   manage_prometheus_path: manage_prometheus_path,
   cluster_id: @cluster.id } }
 
diff --git a/app/workers/all_queues.yml b/app/workers/all_queues.yml
index 3bf46675ad5..5ff1a331b09 100644
--- a/app/workers/all_queues.yml
+++ b/app/workers/all_queues.yml
@@ -75,6 +75,12 @@
   :latency_sensitive: 
   :resource_boundary: :unknown
   :weight: 1
+- :name: cronjob:environments_auto_stop_cron
+  :feature_category: :continuous_delivery
+  :has_external_dependencies: 
+  :latency_sensitive: 
+  :resource_boundary: :unknown
+  :weight: 1
 - :name: cronjob:expire_build_artifacts
   :feature_category: :continuous_integration
   :has_external_dependencies: 
diff --git a/app/workers/environments/auto_stop_cron_worker.rb b/app/workers/environments/auto_stop_cron_worker.rb
new file mode 100644
index 00000000000..8fcda35b414
--- /dev/null
+++ b/app/workers/environments/auto_stop_cron_worker.rb
@@ -0,0 +1,16 @@
+# frozen_string_literal: true
+
+module Environments
+  class AutoStopCronWorker
+    include ApplicationWorker
+    include CronjobQueue # rubocop:disable Scalability/CronWorkerContext
+
+    feature_category :continuous_delivery
+
+    def perform
+      return unless Feature.enabled?(:auto_stop_environments)
+
+      AutoStopService.new.execute
+    end
+  end
+end