Update cleanup policy parameters

* The default worker capacity is bumped to `4`
* Update the related documentation with the current default values

Changelog: changed

app/models/application_setting_implementation.rb

@@ -218,7 +218,8 @@ module ApplicationSettingImplementation
         valid_runner_registrars: VALID_RUNNER_REGISTRAR_TYPES,
         wiki_page_max_content_bytes: 50.megabytes,
         container_registry_delete_tags_service_timeout: 250,
-        container_registry_expiration_policies_worker_capacity: 0,
+        container_registry_expiration_policies_worker_capacity: 4,
+        container_registry_cleanup_tags_service_max_list_size: 200,
         container_registry_import_max_tags_count: 100,
         container_registry_import_max_retries: 3,
         container_registry_import_start_max_retries: 50,

db/migrate/20220215164709_update_application_settings_container_registry_exp_pol_worker_capacity_default.rb

+# frozen_string_literal: true
+class UpdateApplicationSettingsContainerRegistryExpPolWorkerCapacityDefault < Gitlab::Database::Migration[1.0]
+  class Settings < ActiveRecord::Base
+    self.table_name = 'application_settings'
+  end
+
+  def up
+    change_column_default(:application_settings, :container_registry_expiration_policies_worker_capacity, from: 0, to: 4)
+
+    current_settings = Settings.first
+
+    if current_settings&.container_registry_expiration_policies_worker_capacity == 0
+      current_settings.update!(container_registry_expiration_policies_worker_capacity: 4)
+    end
+  end
+
+  def down
+    change_column_default(:application_settings, :container_registry_expiration_policies_worker_capacity, from: 4, to: 0)
+  end
+end

db/schema_migrations/20220215164709

+af6d142b77bc2787a520f8cbc63c287823a7a65a2edb3eb488e4f0f4efde9fa8
\ No newline at end of file

db/structure.sql

@@ -10528,7 +10528,7 @@ CREATE TABLE application_settings (
     automatic_purchased_storage_allocation boolean DEFAULT false NOT NULL,
     encrypted_ci_jwt_signing_key text,
     encrypted_ci_jwt_signing_key_iv text,
-    container_registry_expiration_policies_worker_capacity integer DEFAULT 0 NOT NULL,
+    container_registry_expiration_policies_worker_capacity integer DEFAULT 4 NOT NULL,
     elasticsearch_analyzers_smartcn_enabled boolean DEFAULT false NOT NULL,
     elasticsearch_analyzers_smartcn_search boolean DEFAULT false NOT NULL,
     elasticsearch_analyzers_kuromoji_enabled boolean DEFAULT false NOT NULL,

doc/user/packages/container_registry/reduce_container_registry_storage.md

@@ -182,11 +182,16 @@ the process can take time to finish.
 
 To prevent server resource starvation, the following application settings are available:
 
-- `container_registry_expiration_policies_worker_capacity`. The maximum number of cleanup workers running concurrently. This must be greater than `1`.
-   We recommend starting with a low number and increasing it after monitoring the resources used by the background workers.
-- `container_registry_delete_tags_service_timeout`. The maximum time, in seconds, that the cleanup process can take to delete a batch of tags.
-- `container_registry_cleanup_tags_service_max_list_size`. The maximum number of tags that can be deleted in a single execution. Additional tags must be deleted in another execution.
-   We recommend starting with a low number, like `100`, and increasing it after monitoring that container images are properly deleted.
+- `container_registry_expiration_policies_worker_capacity`: the maximum number of cleanup workers
+  running concurrently. This must be greater than or equal to `0`. We recommend starting with a low
+  number and increasing it after monitoring the resources used by the background workers. To remove
+  all workers and not execute the cleanup policies, set this to `0`. The default value is `4`.
+- `container_registry_delete_tags_service_timeout`: the maximum time (in seconds) that the cleanup
+  process can take to delete a batch of tags. The default value is `250`.
+- `container_registry_cleanup_tags_service_max_list_size`: the maximum number of tags that can be
+  deleted in a single execution. Additional tags must be deleted in another execution. We recommend
+  starting with a low number and increasing it after monitoring that container images are properly
+  deleted. The default value is `200`.
 
 For self-managed instances, those settings can be updated in the [Rails console](../../../administration/operations/rails_console.md#starting-a-rails-console-session):
 

spec/migrations/update_application_settings_container_registry_exp_pol_worker_capacity_default_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+require_migration!
+
+RSpec.describe UpdateApplicationSettingsContainerRegistryExpPolWorkerCapacityDefault do
+  let(:settings) { table(:application_settings) }
+
+  context 'with no rows in the application_settings table' do
+    it 'does not insert a row' do
+      expect { migrate! }.to not_change { settings.count }
+    end
+  end
+
+  context 'with a row in the application_settings table' do
+    before do
+      settings.create!(container_registry_expiration_policies_worker_capacity: capacity)
+    end
+
+    context 'with container_registry_expiration_policy_worker_capacity set to a value different than 0' do
+      let(:capacity) { 1 }
+
+      it 'does not update the row' do
+        expect { migrate! }
+          .to not_change { settings.count }
+          .and not_change { settings.first.container_registry_expiration_policies_worker_capacity }
+      end
+    end
+
+    context 'with container_registry_expiration_policy_worker_capacity set to 0' do
+      let(:capacity) { 0 }
+
+      it 'updates the existing row' do
+        expect { migrate! }
+          .to not_change { settings.count }
+          .and change { settings.first.container_registry_expiration_policies_worker_capacity }.from(0).to(4)
+      end
+    end
+  end
+end