Allow user to be assigned to escalation rule

db/migrate/20210722074220_remove_null_constraint_on_schedule_from_escalation_rules.rb

+# frozen_string_literal: true
+
+class RemoveNullConstraintOnScheduleFromEscalationRules < ActiveRecord::Migration[6.1]
+  def up
+    change_column_null :incident_management_escalation_rules, :oncall_schedule_id, true
+  end
+
+  def down
+    exec_query 'DELETE FROM incident_management_escalation_rules WHERE oncall_schedule_id IS NULL'
+
+    change_column_null :incident_management_escalation_rules, :oncall_schedule_id, false
+  end
+end

db/migrate/20210722074242_add_user_to_escalation_rules.rb

+# frozen_string_literal: true
+
+class AddUserToEscalationRules < ActiveRecord::Migration[6.1]
+  include Gitlab::Database::MigrationHelpers
+
+  def up
+    with_lock_retries do
+      add_column :incident_management_escalation_rules, :user_id, :bigint, null: true
+    end
+  end
+
+  def down
+    with_lock_retries do
+      remove_column :incident_management_escalation_rules, :user_id
+    end
+  end
+end

db/migrate/20210722074256_add_user_index_to_escalation_rules.rb

+# frozen_string_literal: true
+
+class AddUserIndexToEscalationRules < ActiveRecord::Migration[6.1]
+  include Gitlab::Database::MigrationHelpers
+
+  disable_ddl_transaction!
+
+  USER_INDEX_NAME = 'index_escalation_rules_on_user'
+  OLD_UNIQUE_INDEX_NAME = 'index_on_policy_schedule_status_elapsed_time_escalation_rules'
+  NEW_UNIQUE_INDEX_NAME = 'index_escalation_rules_on_all_attributes'
+
+  def up
+    remove_concurrent_index_by_name :incident_management_escalation_rules, OLD_UNIQUE_INDEX_NAME
+
+    add_concurrent_index :incident_management_escalation_rules, :user_id, name: USER_INDEX_NAME
+    add_concurrent_index :incident_management_escalation_rules,
+      [:policy_id, :oncall_schedule_id, :status, :elapsed_time_seconds, :user_id],
+      unique: true,
+      name: NEW_UNIQUE_INDEX_NAME
+  end
+
+  def down
+    remove_concurrent_index_by_name :incident_management_escalation_rules, USER_INDEX_NAME
+    remove_concurrent_index_by_name :incident_management_escalation_rules, NEW_UNIQUE_INDEX_NAME
+
+    exec_query 'DELETE FROM incident_management_escalation_rules WHERE oncall_schedule_id IS NULL'
+
+    add_concurrent_index :incident_management_escalation_rules,
+      [:policy_id, :oncall_schedule_id, :status, :elapsed_time_seconds],
+      unique: true,
+      name: OLD_UNIQUE_INDEX_NAME
+  end
+end

db/migrate/20210722074309_add_user_fk_to_escalation_rules.rb

+# frozen_string_literal: true
+
+class AddUserFkToEscalationRules < ActiveRecord::Migration[6.1]
+  include Gitlab::Database::MigrationHelpers
+
+  disable_ddl_transaction!
+
+  def up
+    add_concurrent_foreign_key :incident_management_escalation_rules, :users, column: :user_id, on_delete: :cascade
+  end
+
+  def down
+    with_lock_retries do
+      remove_foreign_key_if_exists :incident_management_escalation_rules, column: :user_id
+    end
+  end
+end

db/migrate/20210722074339_add_xor_check_constraint_for_escalation_rules.rb

+# frozen_string_literal: true
+
+class AddXorCheckConstraintForEscalationRules < ActiveRecord::Migration[6.1]
+  include Gitlab::Database::MigrationHelpers
+
+  disable_ddl_transaction!
+
+  CONSTRAINT_NAME = 'escalation_rules_one_of_oncall_schedule_or_user'
+
+  def up
+    add_check_constraint :incident_management_escalation_rules, 'num_nonnulls(oncall_schedule_id, user_id) = 1', CONSTRAINT_NAME
+  end
+
+  def down
+    remove_check_constraint :incident_management_escalation_rules, CONSTRAINT_NAME
+  end
+end

db/schema_migrations/20210722074220

+cf276b9aa97fc7857499e1b103a8e09eda329a4db92d0e653cc6f7128987be39
\ No newline at end of file

db/schema_migrations/20210722074242

+5c6aff5b43a1e81e84a42f008a8a1ab90c77ee450884aa1ecc86bce551424f43
\ No newline at end of file

db/schema_migrations/20210722074256

+d49b1f48c2fa1cac8d7793f8bb025792f4bb85eed787ba3abdbaa4647523b70a
\ No newline at end of file

db/schema_migrations/20210722074309

+eab0f8488b0122ec6c5625c66ebcbd221579bdd9cc2cf670d1f26181709f23b7
\ No newline at end of file

db/schema_migrations/20210722074339

+a7a6697d86b71d59104af35a9d7d6f3caebf4ee1252e4f3e52133afb3f642e48
\ No newline at end of file

db/structure.sql

@@ -13941,10 +13941,12 @@ ALTER SEQUENCE incident_management_escalation_policies_id_seq OWNED BY incident_
 CREATE TABLE incident_management_escalation_rules (
     id bigint NOT NULL,
     policy_id bigint NOT NULL,
-    oncall_schedule_id bigint NOT NULL,
+    oncall_schedule_id bigint,
     status smallint NOT NULL,
     elapsed_time_seconds integer NOT NULL,
-    is_removed boolean DEFAULT false NOT NULL
+    is_removed boolean DEFAULT false NOT NULL,
+    user_id bigint,
+    CONSTRAINT escalation_rules_one_of_oncall_schedule_or_user CHECK ((num_nonnulls(oncall_schedule_id, user_id) = 1))
 );
 
 CREATE SEQUENCE incident_management_escalation_rules_id_seq
@@ -23723,6 +23725,10 @@ CREATE INDEX index_esc_protected_branches_on_external_status_check_id ON externa
 
 CREATE INDEX index_esc_protected_branches_on_protected_branch_id ON external_status_checks_protected_branches USING btree (protected_branch_id);
 
+CREATE UNIQUE INDEX index_escalation_rules_on_all_attributes ON incident_management_escalation_rules USING btree (policy_id, oncall_schedule_id, status, elapsed_time_seconds, user_id);
+
+CREATE INDEX index_escalation_rules_on_user ON incident_management_escalation_rules USING btree (user_id);
+
 CREATE INDEX index_events_on_action ON events USING btree (action);
 
 CREATE INDEX index_events_on_author_id_and_created_at ON events USING btree (author_id, created_at);
@@ -24441,8 +24447,6 @@ CREATE INDEX index_on_oncall_schedule_escalation_rule ON incident_management_esc
 
 CREATE INDEX index_on_pages_metadata_not_migrated ON project_pages_metadata USING btree (project_id) WHERE ((deployed = true) AND (pages_deployment_id IS NULL));
 
-CREATE UNIQUE INDEX index_on_policy_schedule_status_elapsed_time_escalation_rules ON incident_management_escalation_rules USING btree (policy_id, oncall_schedule_id, status, elapsed_time_seconds);
-
 CREATE UNIQUE INDEX index_on_project_id_escalation_policy_name_unique ON incident_management_escalation_policies USING btree (project_id, name);
 
 CREATE INDEX index_on_projects_lower_path ON projects USING btree (lower((path)::text));
@@ -25895,6 +25899,9 @@ ALTER TABLE ONLY epics
 ALTER TABLE ONLY clusters_applications_runners
     ADD CONSTRAINT fk_02de2ded36 FOREIGN KEY (runner_id) REFERENCES ci_runners(id) ON DELETE SET NULL;
 
+ALTER TABLE ONLY incident_management_escalation_rules
+    ADD CONSTRAINT fk_0314ee86eb FOREIGN KEY (user_id) REFERENCES users(id) ON DELETE CASCADE;
+
 ALTER TABLE ONLY design_management_designs_versions
     ADD CONSTRAINT fk_03c671965c FOREIGN KEY (design_id) REFERENCES design_management_designs(id) ON DELETE CASCADE;
 

doc/api/graphql/reference/index.md

@@ -9219,6 +9219,7 @@ Represents an escalation rule for an escalation policy.
 | <a id="escalationruletypeid"></a>`id` | [`IncidentManagementEscalationRuleID`](#incidentmanagementescalationruleid) | ID of the escalation policy. |
 | <a id="escalationruletypeoncallschedule"></a>`oncallSchedule` | [`IncidentManagementOncallSchedule`](#incidentmanagementoncallschedule) | The on-call schedule to notify. |
 | <a id="escalationruletypestatus"></a>`status` | [`EscalationRuleStatus`](#escalationrulestatus) | The status required to prevent the rule from activating. |
+| <a id="escalationruletypeuser"></a>`user` | [`UserCore`](#usercore) | The user to notify. |
 
 ### `Event`
 
@@ -16737,8 +16738,9 @@ Represents an escalation rule.
 | Name | Type | Description |
 | ---- | ---- | ----------- |
 | <a id="escalationruleinputelapsedtimeseconds"></a>`elapsedTimeSeconds` | [`Int!`](#int) | The time in seconds before the rule is activated. |
-| <a id="escalationruleinputoncallscheduleiid"></a>`oncallScheduleIid` | [`ID!`](#id) | The on-call schedule to notify. |
+| <a id="escalationruleinputoncallscheduleiid"></a>`oncallScheduleIid` | [`ID`](#id) | The on-call schedule to notify. |
 | <a id="escalationruleinputstatus"></a>`status` | [`EscalationRuleStatus!`](#escalationrulestatus) | The status required to prevent the rule from activating. |
+| <a id="escalationruleinputusername"></a>`username` | [`String`](#string) | The username of the user to notify. |
 
 ### `JiraUsersMappingInputType`
 

ee/app/graphql/mutations/incident_management/escalation_policy/base.rb

@@ -43,23 +43,42 @@ module Mutations
         def prepare_rules_attributes(project, args)
           return args unless rules = args.delete(:rules)
 
-          iids = rules.collect { |rule| rule[:oncall_schedule_iid] }
-          found_schedules = schedules_for_iids(project, iids)
-          rules_attributes = rules.map { |rule| prepare_rule(found_schedules, rule.to_h) }
+          schedules = find_schedules(project, rules)
+          users = find_users(rules)
+          rules_attributes = rules.map { |rule| prepare_rule(rule.to_h, schedules, users) }
 
           args.merge(rules_attributes: rules_attributes)
         end
 
-        def prepare_rule(schedules, rule)
+        def prepare_rule(rule, schedules, users)
           iid = rule.delete(:oncall_schedule_iid).to_i
+          username = rule.delete(:username)
 
-          rule.merge(oncall_schedule: schedules[iid])
+          rule.merge(
+            oncall_schedule: schedules[iid],
+            user: users[username]
+          )
         end
 
-        def schedules_for_iids(project, iids)
-          schedules = ::IncidentManagement::OncallSchedulesFinder.new(current_user, project, iid: iids).execute
+        def find_schedules(project, rules)
+          find_resource(rules, :oncall_schedule_iid) do |iids|
+            ::IncidentManagement::OncallSchedulesFinder.new(current_user, project, iid: iids).execute.index_by(&:iid)
+          end
+        end
+
+        def find_users(rules)
+          find_resource(rules, :username) do |usernames|
+            UsersFinder.new(current_user, username: usernames).execute.index_by(&:username)
+          end
+        end
+
+        def find_resource(rules, attribute)
+          identifiers = rules.collect { |rule| rule[attribute] }.uniq.compact
+          resources = yield(identifiers)
+
+          return resources if resources.length == identifiers.length
 
-          schedules.index_by(&:iid)
+          raise_resource_not_available_error!
         end
       end
     end

ee/app/graphql/types/incident_management/escalation_rule_input_type.rb

@@ -8,7 +8,11 @@ module Types
 
       argument :oncall_schedule_iid, GraphQL::Types::ID, # rubocop: disable Graphql/IDType
         description: 'The on-call schedule to notify.',
-        required: true
+        required: false
+
+      argument :username, GraphQL::Types::String,
+        description: 'The username of the user to notify.',
+        required: false
 
       argument :elapsed_time_seconds, GraphQL::Types::Int,
         description: 'The time in seconds before the rule is activated.',
@@ -17,6 +21,18 @@ module Types
       argument :status, Types::IncidentManagement::EscalationRuleStatusEnum,
         description: 'The status required to prevent the rule from activating.',
         required: true
+
+      def prepare
+        unless schedule_iid_or_username
+          raise Gitlab::Graphql::Errors::ArgumentError, 'One of oncall_schedule_iid or username must be provided'
+        end
+
+        super
+      end
+
+      def schedule_iid_or_username
+        oncall_schedule_iid.present? ^ username.present?
+      end
     end
   end
 end

ee/app/graphql/types/incident_management/escalation_rule_type.rb

@@ -15,6 +15,10 @@ module Types
             null: true,
             description: 'The on-call schedule to notify.'
 
+      field :user, Types::UserType,
+            null: true,
+            description: 'The user to notify.'
+
       field :elapsed_time_seconds, GraphQL::Types::Int,
             null: true,
             description: 'The time in seconds before the rule is activated.'

ee/app/models/incident_management/escalation_policy.rb

@@ -11,7 +11,6 @@ module IncidentManagement
     validates :project_id, uniqueness: { message: _('can only have one escalation policy') }, on: :create
     validates :name, presence: true, uniqueness: { scope: [:project_id] }, length: { maximum: 72 }
     validates :description, length: { maximum: 160 }
-    validates :rules, presence: true
 
     accepts_nested_attributes_for :rules
   end

ee/app/models/incident_management/escalation_rule.rb

@@ -5,19 +5,35 @@ module IncidentManagement
     self.table_name = 'incident_management_escalation_rules'
 
     belongs_to :policy, class_name: 'EscalationPolicy', inverse_of: 'rules', foreign_key: 'policy_id'
-    belongs_to :oncall_schedule, class_name: 'OncallSchedule', inverse_of: 'rotations', foreign_key: 'oncall_schedule_id'
+    belongs_to :oncall_schedule, class_name: 'OncallSchedule', foreign_key: 'oncall_schedule_id', optional: true
+    belongs_to :user, optional: true
 
     enum status: AlertManagement::Alert::STATUSES.slice(:acknowledged, :resolved)
 
     validates :status, presence: true
-    validates :oncall_schedule, presence: true
     validates :elapsed_time_seconds,
               presence: true,
               numericality: { only_integer: true, greater_than_or_equal_to: 0, less_than_or_equal_to: 24.hours }
 
-    validates :policy_id, uniqueness: { scope: [:oncall_schedule_id, :status, :elapsed_time_seconds], message: _('must have a unique schedule, status, and elapsed time') }
+    validate :schedule_or_rule_present
+    validates :oncall_schedule_id,
+              uniqueness: { scope: [:policy_id, :status, :elapsed_time_seconds],
+              message: _('must be unique by status and elapsed time within a policy') },
+              allow_nil: true
+    validates :user_id,
+              uniqueness: { scope: [:policy_id, :status, :elapsed_time_seconds],
+              message: _('must be unique by status and elapsed time within a policy') },
+              allow_nil: true
 
     scope :not_removed, -> { where(is_removed: false) }
     scope :removed, -> { where(is_removed: true) }
+
+    private
+
+    def schedule_or_rule_present
+      unless oncall_schedule.present? ^ user.present?
+        errors.add(:base, 'must have either an on-call schedule or user')
+      end
+    end
   end
 end

ee/app/services/incident_management/escalation_policies/base_service.rb

@@ -14,7 +14,13 @@ module IncidentManagement
       end
 
       def invalid_schedules?
-        params[:rules_attributes]&.any? { |attrs| attrs[:oncall_schedule]&.project != project }
+        params[:rules_attributes]&.any? { |attrs| attrs[:oncall_schedule] && attrs[:oncall_schedule].project != project }
+      end
+
+      def users_without_permissions?
+        DeclarativePolicy.subject_scope do
+          params[:rules_attributes]&.any? { |attrs| attrs[:user] && !attrs[:user].can?(:read_project, project) }
+        end
       end
 
       def error(message)
@@ -38,7 +44,11 @@ module IncidentManagement
       end
 
       def error_bad_schedules
-        error(_('All escalations rules must have a schedule in the same project as the policy'))
+        error(_('Schedule-based escalation rules must have a schedule in the same project as the policy'))
+      end
+
+      def error_user_without_permission
+        error(_('User-based escalation rules must have a user with access to the project'))
       end
 
       def error_in_save(policy)

ee/app/services/incident_management/escalation_policies/create_service.rb

@@ -23,6 +23,7 @@ module IncidentManagement
         return error_no_rules if params[:rules_attributes].blank?
         return error_too_many_rules if too_many_rules?
         return error_bad_schedules if invalid_schedules?
+        return error_user_without_permission if users_without_permissions?
 
         escalation_policy = project.incident_management_escalation_policies.create(params)
 

ee/app/services/incident_management/escalation_policies/update_service.rb

@@ -28,6 +28,7 @@ module IncidentManagement
         return error_no_rules if empty_rules?
         return error_too_many_rules if too_many_rules?
         return error_bad_schedules if invalid_schedules?
+        return error_user_without_permission if users_without_permissions?
 
         reconcile_rules!
 
@@ -85,7 +86,7 @@ module IncidentManagement
       end
 
       def unique_id(rule)
-        rule.slice(:oncall_schedule_id, :elapsed_time_seconds, :status)
+        rule.slice(:oncall_schedule_id, :user_id, :elapsed_time_seconds, :status)
       end
     end
   end

ee/app/services/incident_management/pending_escalations/process_service.rb

@@ -55,8 +55,12 @@ module IncidentManagement
 
       def oncall_notification_recipients
         strong_memoize(:oncall_notification_recipients) do
-          ::IncidentManagement::OncallUsersFinder.new(project, schedule: rule.oncall_schedule).execute.to_a
+          rule.user_id ? [rule.user] : schedule_recipients
+        end
       end
+
+      def schedule_recipients
+        ::IncidentManagement::OncallUsersFinder.new(project, schedule: rule.oncall_schedule).execute.to_a
       end
 
       def destroy_escalation!

ee/spec/factories/incident_management/escalation_rules.rb

@@ -2,7 +2,7 @@
 
 FactoryBot.define do
   factory :incident_management_escalation_rule, class: 'IncidentManagement::EscalationRule' do
-    policy { association :incident_management_escalation_policy }
+    policy { association :incident_management_escalation_policy, rule_count: 0 }
     oncall_schedule { association :incident_management_oncall_schedule, project: policy.project }
     status { IncidentManagement::EscalationRule.statuses[:acknowledged] }
     elapsed_time_seconds { 5.minutes }
@@ -15,5 +15,10 @@ FactoryBot.define do
     trait :removed do
       is_removed { true }
     end
+
+    trait :with_user do
+      oncall_schedule {}
+      user { association :user, developer_projects: [policy.project] }
+    end
   end
 end

ee/spec/graphql/mutations/incident_management/escalation_policy/create_spec.rb

@@ -19,7 +19,7 @@ RSpec.describe Mutations::IncidentManagement::EscalationPolicy::Create do
           status: ::IncidentManagement::EscalationRule.statuses[:acknowledged]
         },
         {
-          oncall_schedule_iid: oncall_schedule.iid,
+          username: current_user&.username,
           elapsed_time_seconds: 600,
           status: ::IncidentManagement::EscalationRule.statuses[:resolved]
         }
@@ -71,8 +71,8 @@ RSpec.describe Mutations::IncidentManagement::EscalationPolicy::Create do
 
           expect(rules.size).to eq(2)
           expect(rules).to match_array([
-            have_attributes(oncall_schedule_id: oncall_schedule.id, elapsed_time_seconds: 300, status: 'acknowledged'),
-            have_attributes(oncall_schedule_id: oncall_schedule.id, elapsed_time_seconds: 600, status: 'resolved')
+            have_attributes(oncall_schedule_id: oncall_schedule.id, user: nil, elapsed_time_seconds: 300, status: 'acknowledged'),
+            have_attributes(oncall_schedule_id: nil, user: current_user, elapsed_time_seconds: 600, status: 'resolved')
           ])
         end
 
@@ -91,7 +91,7 @@ RSpec.describe Mutations::IncidentManagement::EscalationPolicy::Create do
             args[:rules][0][:oncall_schedule_iid] = other_schedule.iid
           end
 
-          it_behaves_like 'returns a GraphQL error', 'All escalations rules must have a schedule in the same project as the policy'
+          it_behaves_like 'raises a resource not available error'
 
           context 'user does not have permission for project' do
             before do
@@ -101,6 +101,14 @@ RSpec.describe Mutations::IncidentManagement::EscalationPolicy::Create do
             it_behaves_like 'raises a resource not available error'
           end
         end
+
+        context 'user for rule does not exist' do
+          before do
+            args[:rules][1][:username] = 'junk-username'
+          end
+
+          it_behaves_like 'raises a resource not available error'
+        end
       end
 
       context 'user does not have permission for project' do

ee/spec/graphql/mutations/incident_management/escalation_policy/update_spec.rb

@@ -110,6 +110,7 @@ RSpec.describe Mutations::IncidentManagement::EscalationPolicy::Update do
 
     context 'with rule updates' do
       let(:oncall_schedule_iid) { oncall_schedule.iid }
+      let(:username) { reporter.username }
       let(:rule_args) do
         [
           {
@@ -119,6 +120,13 @@ RSpec.describe Mutations::IncidentManagement::EscalationPolicy::Update do
           },
           {
             oncall_schedule_iid: oncall_schedule_iid,
+            username: nil,
+            elapsed_time_seconds: 800,
+            status: :acknowledged
+          },
+          {
+            oncall_schedule_iid: nil,
+            username: username,
             elapsed_time_seconds: 800,
             status: :acknowledged
           }
@@ -128,22 +136,17 @@ RSpec.describe Mutations::IncidentManagement::EscalationPolicy::Update do
       let(:expected_rules) do
         [
           first_rule,
-          have_attributes(oncall_schedule_id: oncall_schedule.id, elapsed_time_seconds: 800, status: 'acknowledged')
+          have_attributes(oncall_schedule_id: oncall_schedule.id, user: nil, elapsed_time_seconds: 800, status: 'acknowledged'),
+          have_attributes(oncall_schedule_id: nil, user: reporter, elapsed_time_seconds: 800, status: 'acknowledged')
         ]
       end
 
       it_behaves_like 'successful update with no errors'
 
       context 'when schedule does not exist' do
-        let(:error_message) { eq("The oncall schedule for iid #{non_existing_record_iid} could not be found") }
         let(:oncall_schedule_iid) { non_existing_record_iid }
 
-        it 'returns errors in the body of the response' do
-          expect(resolve).to eq(
-            escalation_policy: nil,
-            errors: ['All escalations rules must have a schedule in the same project as the policy']
-          )
-        end
+        it_behaves_like 'failed update with a top-level access error'
 
         context 'the user does not have permission to update policies regardless' do
           let(:current_user) { reporter }
@@ -151,6 +154,12 @@ RSpec.describe Mutations::IncidentManagement::EscalationPolicy::Update do
           it_behaves_like 'failed update with a top-level access error'
         end
       end
+
+      context "when rule's user does not exist" do
+        let(:username) { 'invalid-username' }
+
+        it_behaves_like 'failed update with a top-level access error'
+      end
     end
   end
 

ee/spec/graphql/types/incident_management/escalation_rule_input_type_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe GitlabSchema.types['EscalationRuleInput'] do
+  context 'mutually exclusive arguments' do
+    let(:input) do
+      {
+        oncall_schedule_iid: schedule_iid,
+        username: username,
+        elapsed_time_seconds: 0,
+        status: 'RESOLVED'
+      }
+    end
+
+    let(:output) { input.merge(status: 'resolved', oncall_schedule_iid: schedule_iid&.to_s) }
+    let(:schedule_iid) {}
+    let(:username) {}
+
+    subject { described_class.coerce_isolated_input(input).to_h }
+
+    context 'with neither username nor schedule provided' do
+      specify { expect { subject }.to raise_error(Gitlab::Graphql::Errors::ArgumentError, 'One of oncall_schedule_iid or username must be provided') }
+    end
+
+    context 'with both username and schedule provided' do
+      let(:schedule_iid) { 3 }
+      let(:username) { 'username' }
+
+      specify { expect { subject }.to raise_error(Gitlab::Graphql::Errors::ArgumentError, 'One of oncall_schedule_iid or username must be provided') }
+    end
+
+    context 'with only on-call schedule provided' do
+      let(:schedule_iid) { 3 }
+
+      it { is_expected.to eq(output) }
+    end
+
+    context 'with only user schedule provided' do
+      let(:username) { 'username' }
+
+      it { is_expected.to eq(output) }
+    end
+  end
+
+  it 'has specific fields' do
+    allowed_args = %w(oncallScheduleIid username elapsedTimeSeconds status)
+
+    expect(described_class.arguments.keys).to include(*allowed_args)
+  end
+end

ee/spec/graphql/types/incident_management/escalation_rule_type_spec.rb

@@ -9,6 +9,7 @@ RSpec.describe GitlabSchema.types['EscalationRuleType'] do
     expected_fields = %i[
       id
       oncall_schedule
+      user
       elapsed_time_seconds
       status
     ]

ee/spec/models/incident_management/escalation_policy_spec.rb

@@ -25,7 +25,6 @@ RSpec.describe IncidentManagement::EscalationPolicy do
 
   describe 'validations' do
     it { is_expected.to validate_presence_of(:name) }
-    it { is_expected.to validate_presence_of(:rules) }
     it { is_expected.to validate_uniqueness_of(:project_id).with_message(/can only have one escalation policy/).on(:create) }
     it { is_expected.to validate_uniqueness_of(:name).scoped_to(:project_id) }
     it { is_expected.to validate_length_of(:name).is_at_most(72) }

ee/spec/models/incident_management/escalation_rule_spec.rb

@@ -3,27 +3,54 @@
 require 'spec_helper'
 
 RSpec.describe IncidentManagement::EscalationRule do
-  let_it_be(:policy) { create(:incident_management_escalation_policy) }
-
-  subject { build(:incident_management_escalation_rule, policy: policy) }
-
-  it { is_expected.to be_valid }
+  subject { build(:incident_management_escalation_rule) }
 
   describe 'associations' do
     it { is_expected.to belong_to(:policy) }
-    it { is_expected.to belong_to(:oncall_schedule) }
+    it { is_expected.to belong_to(:oncall_schedule).optional }
+    it { is_expected.to belong_to(:user).optional }
   end
 
   describe 'validations' do
+    it { is_expected.to be_valid }
     it { is_expected.to validate_presence_of(:status) }
     it { is_expected.to validate_presence_of(:elapsed_time_seconds) }
     it { is_expected.to validate_numericality_of(:elapsed_time_seconds).is_greater_than_or_equal_to(0).is_less_than_or_equal_to(24.hours) }
-    it { is_expected.to validate_uniqueness_of(:policy_id).scoped_to([:oncall_schedule_id, :status, :elapsed_time_seconds] ).with_message('must have a unique schedule, status, and elapsed time') }
+    it { is_expected.to validate_uniqueness_of(:oncall_schedule_id).scoped_to([:policy_id, :status, :elapsed_time_seconds] ).with_message('must be unique by status and elapsed time within a policy') }
+
+    context 'user-based rules' do
+      subject { build(:incident_management_escalation_rule, :with_user) }
+
+      it { is_expected.to be_valid }
+      it { is_expected.to validate_uniqueness_of(:user_id).scoped_to([:policy_id, :status, :elapsed_time_seconds] ).with_message('must be unique by status and elapsed time within a policy') }
+    end
+
+    context 'mutually exclusive attributes' do
+      context 'when user and schedule are both provided' do
+        let_it_be(:schedule) { create(:incident_management_oncall_schedule) }
+
+        subject { build(:incident_management_escalation_rule, :with_user, oncall_schedule: schedule) }
+
+        specify do
+          expect(subject).to be_invalid
+          expect(subject.errors.messages[:base]).to eq(['must have either an on-call schedule or user'])
+        end
+      end
+
+      context 'neither user nor schedule are provided' do
+        subject { build(:incident_management_escalation_rule, oncall_schedule: nil) }
+
+        specify do
+          expect(subject).to be_invalid
+          expect(subject.errors.messages[:base]).to eq(['must have either an on-call schedule or user'])
+        end
+      end
+    end
   end
 
   describe 'scopes' do
-    let_it_be(:rule) { policy.rules.first }
-    let_it_be(:removed_rule) { create(:incident_management_escalation_rule, :removed, policy: policy) }
+    let_it_be(:rule) { create(:incident_management_escalation_rule) }
+    let_it_be(:removed_rule) { create(:incident_management_escalation_rule, :removed, policy: rule.policy) }
 
     describe '.not_removed' do
       subject { described_class.not_removed }

ee/spec/requests/api/graphql/project/incident_management/escalation_policies_spec.rb

@@ -118,7 +118,8 @@ RSpec.describe 'getting Incident Management escalation policies' do
                   'name' => last_policy_rule.oncall_schedule.name,
                   'description' => last_policy_rule.oncall_schedule.description,
                   'timezone' => last_policy_rule.oncall_schedule.timezone
-                }
+                },
+                'user' => nil
               }
             ]
           )

ee/spec/requests/api/graphql/project/incident_management/escalation_policy/rules_spec.rb

@@ -10,6 +10,7 @@ RSpec.describe 'getting Incident Management escalation policies' do
   let_it_be(:policy) { create(:incident_management_escalation_policy, project: project) }
   let_it_be(:rule) { policy.rules.first }
   let_it_be(:schedule) { rule.oncall_schedule }
+  let_it_be(:user_rule) { create(:incident_management_escalation_rule, :with_user, policy: policy) }
 
   let(:params) { {} }
 
@@ -25,6 +26,9 @@ RSpec.describe 'getting Incident Management escalation policies' do
             iid
             name
           }
+          user {
+            username
+          }
         }
       }
     QUERY
@@ -49,15 +53,25 @@ RSpec.describe 'getting Incident Management escalation policies' do
   it 'includes expected data' do
     post_graphql(query, current_user: current_user)
 
-    expect(escalation_rules_response).to eq([{
+    expect(escalation_rules_response).to eq([
+      {
         'id' => global_id(rule),
         'elapsedTimeSeconds' => rule.elapsed_time_seconds, # 5 min
         'status' => rule.status.upcase, # 'ACKNOWLEDGED'
         'oncallSchedule' => {
           'iid' => schedule.iid.to_s,
           'name' => schedule.name
+        },
+        'user' => nil
+      },
+      {
+        'id' => global_id(user_rule),
+        'elapsedTimeSeconds' => user_rule.elapsed_time_seconds, # 5 min
+        'status' => user_rule.status.upcase, # 'ACKNOWLEDGED'
+        'oncallSchedule' => nil,
+        'user' => { 'username' => user_rule.user.username }
       }
-    }])
+    ])
   end
 
   context 'with multiple rules' do
@@ -68,10 +82,11 @@ RSpec.describe 'getting Incident Management escalation policies' do
     it 'orders rules by time and status' do
       post_graphql(query, current_user: current_user)
 
-      expect(escalation_rules_response.length).to eq(4)
+      expect(escalation_rules_response.length).to eq(5)
       expect(escalation_rules_response.map { |rule| rule['id'] }).to eq([
         global_id(earlier_resolved_rule),
         global_id(rule),
+        global_id(user_rule),
         global_id(equivalent_resolved_rule),
         global_id(later_acknowledged_rule)
       ])

ee/spec/services/incident_management/escalation_policies/create_service_spec.rb

@@ -84,20 +84,26 @@ RSpec.describe IncidentManagement::EscalationPolicies::CreateService do
         it_behaves_like 'error response', 'Escalation policies may not have more than 10 rules'
       end
 
-      context 'oncall schedule is blank' do
+      context 'oncall schedule is on the wrong project' do
         before do
-          rule_params[0][:oncall_schedule] = nil
+          rule_params[0][:oncall_schedule] = create(:incident_management_oncall_schedule)
         end
 
-        it_behaves_like 'error response', 'All escalations rules must have a schedule in the same project as the policy'
+        it_behaves_like 'error response', 'Schedule-based escalation rules must have a schedule in the same project as the policy'
       end
 
-      context 'oncall schedule is on the wrong project' do
-        before do
-          rule_params[0][:oncall_schedule] = create(:incident_management_oncall_schedule)
+      context 'user for rule does not have project access' do
+        let(:rule_params) do
+          [
+            {
+              user: create(:user),
+              elapsed_time_seconds: 60,
+              status: :resolved
+            }
+          ]
         end
 
-        it_behaves_like 'error response', 'All escalations rules must have a schedule in the same project as the policy'
+        it_behaves_like 'error response', 'User-based escalation rules must have a user with access to the project'
       end
 
       context 'project has an existing escalation policy' do
@@ -115,6 +121,39 @@ RSpec.describe IncidentManagement::EscalationPolicies::CreateService do
 
         policy = execute.payload[:escalation_policy]
         expect(policy).to be_a(::IncidentManagement::EscalationPolicy)
+        expect(policy.rules.length).to eq(1)
+        expect(policy.rules.first).to have_attributes(
+          oncall_schedule: oncall_schedule,
+          user: nil,
+          elapsed_time_seconds: 60,
+          status: 'resolved'
+        )
+      end
+
+      context 'for a user-based escalation rule' do
+        let(:rule_params) do
+          [
+            {
+              user: user_with_permissions,
+              elapsed_time_seconds: 60,
+              status: :resolved
+            }
+          ]
+        end
+
+        it 'creates the policy and rules' do
+          expect(execute).to be_success
+
+          policy = execute.payload[:escalation_policy]
+          expect(policy).to be_a(::IncidentManagement::EscalationPolicy)
+          expect(policy.rules.length).to eq(1)
+          expect(policy.rules.first).to have_attributes(
+            oncall_schedule: nil,
+            user: user_with_permissions,
+            elapsed_time_seconds: 60,
+            status: 'resolved'
+          )
+        end
       end
     end
   end

ee/spec/services/incident_management/escalation_policies/update_service_spec.rb

@@ -7,8 +7,11 @@ RSpec.describe IncidentManagement::EscalationPolicies::UpdateService do
   let_it_be(:user_without_permissions) { create(:user) }
   let_it_be(:project) { create(:project) }
   let_it_be(:oncall_schedule) { create(:incident_management_oncall_schedule, project: project) }
-  let_it_be_with_reload(:escalation_policy) { create(:incident_management_escalation_policy, project: project, rule_count: 2) }
-  let_it_be_with_reload(:escalation_rules) { escalation_policy.rules }
+
+  let_it_be_with_reload(:escalation_policy) { create(:incident_management_escalation_policy, project: project) }
+  let_it_be_with_reload(:schedule_escalation_rule) { escalation_policy.rules.first }
+  let_it_be_with_reload(:user_escalation_rule) { create(:incident_management_escalation_rule, :with_user, policy: escalation_policy) }
+  let_it_be_with_reload(:escalation_rules) { escalation_policy.reload.rules }
 
   let(:service) { described_class.new(escalation_policy, current_user, params) }
   let(:current_user) { user_with_permissions }
@@ -24,14 +27,16 @@ RSpec.describe IncidentManagement::EscalationPolicies::UpdateService do
   let(:rule_params) { [*existing_rules_params, new_rule_params] }
   let(:existing_rules_params) do
     escalation_rules.map do |rule|
-      rule.slice(:oncall_schedule, :elapsed_time_seconds)
+      rule.slice(:oncall_schedule, :user, :elapsed_time_seconds)
           .merge(status: rule.status.to_sym)
     end
   end
 
+  let(:user_for_rule) {}
   let(:new_rule_params) do
     {
       oncall_schedule: oncall_schedule,
+      user: user_for_rule,
       elapsed_time_seconds: 800,
       status: :acknowledged
     }
@@ -94,6 +99,13 @@ RSpec.describe IncidentManagement::EscalationPolicies::UpdateService do
       let(:expected_rules) { [*escalation_rules, new_rule] }
 
       it_behaves_like 'successful update with no errors'
+
+      context 'with a user-based rule' do
+        let(:oncall_schedule) { nil }
+        let(:user_for_rule) { user_with_permissions }
+
+        it_behaves_like 'successful update with no errors'
+      end
     end
 
     context 'when all old rules are replaced' do
@@ -166,17 +178,18 @@ RSpec.describe IncidentManagement::EscalationPolicies::UpdateService do
       it_behaves_like 'error response', 'Escalation policies may not have more than 10 rules'
     end
 
-    context 'when the on-call schedule is not present on the rule' do
-      let(:rule_params) { [new_rule_params.except(:oncall_schedule)] }
-
-      it_behaves_like 'error response', 'All escalations rules must have a schedule in the same project as the policy'
-    end
-
     context 'when the on-call schedule is not on the project' do
       let(:other_schedule) { create(:incident_management_oncall_schedule) }
       let(:rule_params) { [new_rule_params.merge(oncall_schedule: other_schedule)] }
 
-      it_behaves_like 'error response', 'All escalations rules must have a schedule in the same project as the policy'
+      it_behaves_like 'error response', 'Schedule-based escalation rules must have a schedule in the same project as the policy'
+    end
+
+    context "when the rule's user does not have access to the project" do
+      let(:oncall_schedule) { nil }
+      let(:user_for_rule) { user_without_permissions }
+
+      it_behaves_like 'error response', 'User-based escalation rules must have a user with access to the project'
     end
 
     context 'when an error occurs during update' do

ee/spec/services/incident_management/pending_escalations/process_service_spec.rb

@@ -7,7 +7,7 @@ RSpec.describe IncidentManagement::PendingEscalations::ProcessService do
   let_it_be(:schedule_1) { create(:incident_management_oncall_schedule, :with_rotation, project: project) }
   let_it_be(:schedule_1_users) { schedule_1.participants.map(&:user) }
 
-  let(:escalation_rule) { build(:incident_management_escalation_rule, oncall_schedule: schedule_1 ) }
+  let(:escalation_rule) { build(:incident_management_escalation_rule, oncall_schedule: schedule_1) }
   let!(:escalation_policy) { create(:incident_management_escalation_policy, project: project, rules: [escalation_rule]) }
 
   let(:alert) { create(:alert_management_alert, project: project, **alert_params) }
@@ -55,6 +55,14 @@ RSpec.describe IncidentManagement::PendingEscalations::ProcessService do
 
         expect { execute }.to change(Note, :count).by(1)
       end
+
+      context 'when escalation rule is for a user' do
+        let(:escalation_rule) { build(:incident_management_escalation_rule, :with_user) }
+        let(:users) { [escalation_rule.user] }
+
+        it_behaves_like 'sends on-call notification'
+        it_behaves_like 'deletes the escalation'
+      end
     end
 
     context 'target is already resolved' do

locale/gitlab.pot

@@ -3252,9 +3252,6 @@ msgstr ""
 msgid "All epics"
 msgstr ""
 
-msgid "All escalations rules must have a schedule in the same project as the policy"
-msgstr ""
-
 msgid "All groups and projects"
 msgstr ""
 
@@ -28823,6 +28820,9 @@ msgstr ""
 msgid "Schedule a new pipeline"
 msgstr ""
 
+msgid "Schedule-based escalation rules must have a schedule in the same project as the policy"
+msgstr ""
+
 msgid "Scheduled"
 msgstr ""
 
@@ -35992,6 +35992,9 @@ msgstr ""
 msgid "User was successfully updated."
 msgstr ""
 
+msgid "User-based escalation rules must have a user with access to the project"
+msgstr ""
+
 msgid "UserAvailability|%{author} %{spanStart}(Busy)%{spanEnd}"
 msgstr ""
 
@@ -39604,7 +39607,7 @@ msgstr ""
 msgid "must be inside the fork network"
 msgstr ""
 
-msgid "must have a unique schedule, status, and elapsed time"
+msgid "must be unique by status and elapsed time within a policy"
 msgstr ""
 
 msgid "my-awesome-group"