Add removed_at to oncall participants table

- Add migrations
- Add specs for new methods
- Update code to use new scopes

db/migrate/20210222030537_add_removed_at_to_oncall_participant.rb

+# frozen_string_literal: true
+
+class AddRemovedAtToOncallParticipant < ActiveRecord::Migration[6.0]
+  include Gitlab::Database::MigrationHelpers
+
+  DOWNTIME = false
+
+  def up
+    with_lock_retries do
+      add_column :incident_management_oncall_participants, :removed_at, :datetime_with_timezone
+    end
+  end
+
+  def down
+    remove_column :incident_management_oncall_participants, :removed_at
+  end
+end
+
+

db/migrate/20210222042745_add_removed_at_to_oncall_participant_index.rb

+# frozen_string_literal: true
+
+class AddRemovedAtToOncallParticipantIndex < ActiveRecord::Migration[6.0]
+  include Gitlab::Database::MigrationHelpers
+
+  DOWNTIME = false
+  disable_ddl_transaction!
+
+  def up
+    add_concurrent_index :incident_management_oncall_participants, :removed_at
+  end
+
+  def down
+    remove_concurrent_index :incident_management_oncall_participants, :removed_at
+  end
+end

db/schema_migrations/20210222030537

+44b0e2b3e32e45fb557a5c9c41f69de94a5d41bad43267f00090b9c527b2b1e1
\ No newline at end of file

db/schema_migrations/20210222042745

+88bbd8cbc4398c3c05a834c4d8d36ee55aca9d698da3cf3c1df0afe916bc051f
\ No newline at end of file

db/structure.sql

@@ -13233,7 +13233,8 @@ CREATE TABLE incident_management_oncall_participants (
     oncall_rotation_id bigint NOT NULL,
     user_id bigint NOT NULL,
     color_palette smallint NOT NULL,
-    color_weight smallint NOT NULL
+    color_weight smallint NOT NULL,
+    removed_at timestamp with time zone
 );
 
 CREATE SEQUENCE incident_management_oncall_participants_id_seq
@@ -22460,6 +22461,7 @@ CREATE UNIQUE INDEX index_inc_mgmnt_oncall_rotations_on_oncall_schedule_id_and_n
 CREATE INDEX index_incident_management_oncall_schedules_on_project_id ON incident_management_oncall_schedules USING btree (project_id);
 
 CREATE INDEX index_incident_management_oncall_shifts_on_participant_id ON incident_management_oncall_shifts USING btree (participant_id);
+CREATE INDEX index_incident_management_oncall_participants_on_removed_at ON incident_management_oncall_participants USING btree (removed_at);
 
 CREATE UNIQUE INDEX index_index_statuses_on_project_id ON index_statuses USING btree (project_id);
 

ee/app/models/incident_management/oncall_participant.rb

@@ -20,5 +20,12 @@ module IncidentManagement
     validates :user, presence: true, uniqueness: { scope: :oncall_rotation_id }
 
     delegate :project, to: :rotation, allow_nil: true
+
+    scope :not_removed, -> { where(removed_at: nil) }
+    scope :removed, -> { where('removed_at is NOT NULL') }
+
+    def mark_as_removed
+      update_column(:removed_at, Time.current)
+    end
   end
 end

ee/lib/incident_management/oncall_shift_generator.rb

@@ -19,7 +19,7 @@ module IncidentManagement
       ends_at = limit_end_time(apply_timezone(ends_at))
 
       return [] unless starts_at < ends_at
-      return [] unless rotation.participants.any?
+      return [] unless participants.any?
 
       # The first shift within the timeframe may begin before
       # the timeframe. We want to begin generating shifts
@@ -50,7 +50,7 @@ module IncidentManagement
 
       return if timestamp < rotation_starts_at
       return if rotation_ends_at && rotation_ends_at <= timestamp
-      return unless rotation.participants.any?
+      return unless participants.any?
 
       elapsed_shift_cycle_count = elapsed_whole_shift_cycles(timestamp)
       shift_cycle_starts_at = shift_cycle_start_time(elapsed_shift_cycle_count)
@@ -175,7 +175,7 @@ module IncidentManagement
 
     def participants
       strong_memoize(:participants) do
-        rotation.participants
+        rotation.participants.not_removed
       end
     end
 

ee/spec/factories/incident_management/oncall_participant.rb

@@ -12,5 +12,9 @@ FactoryBot.define do
         participant.rotation.project.add_developer(participant.user)
       end
     end
+
+    trait :removed do
+      removed_at { Time.current }
+    end
   end
 end

ee/spec/models/incident_management/oncall_participant_spec.rb

@@ -5,6 +5,7 @@ require 'spec_helper'
 RSpec.describe IncidentManagement::OncallParticipant do
   let_it_be(:rotation) { create(:incident_management_oncall_rotation) }
   let_it_be(:user) { create(:user) }
+  let_it_be(:participant) { create(:incident_management_oncall_participant, rotation: rotation) }
 
   subject { build(:incident_management_oncall_participant, rotation: rotation, user: user) }
 
@@ -38,6 +39,34 @@ RSpec.describe IncidentManagement::OncallParticipant do
     end
   end
 
+  describe 'scopes' do
+    let_it_be(:removed) { create(:incident_management_oncall_participant, :removed, rotation: rotation) }
+
+    describe '.not_removed' do
+      subject { described_class.not_removed }
+
+      it { is_expected.to contain_exactly(participant) }
+    end
+
+    describe '.removed' do
+      subject { described_class.removed }
+
+      it { is_expected.to contain_exactly(removed) }
+    end
+  end
+
+  describe '#mark_as_removed' do
+    around do |example|
+      freeze_time { example.run }
+    end
+
+    subject { participant.mark_as_removed }
+
+    it 'updates removed_at to the current time' do
+      expect { subject }.to change { participant.reload.removed_at }.to(Time.current)
+    end
+  end
+
   private
 
   def remove_user_from_project(user, project)