• Add a new cascading setting to groups only
• Convenience methods
  • Attribute reader method (delayed_project_removal)
  • _locked? method
• Add a new cascading setting to projects
  • Background
  • Implementation
• Cascading setting values on write
  • Legacy cascading settings writes
  • Recommendation for cascading settings writes going forward
• Display cascading settings on the frontend
  • Rails view helpers
  • HAML partials
  • JavaScript
  • Put it all together
  • Vue
  • Using Vue
  • Reasoning for supporing both HAML and Vue

Cascading Settings

Have you ever wanted to add a setting on a GitLab project and/or group that had a default value that was inherited from a parent in the hierarchy?

If so: we have the framework you have been seeking!

The cascading settings framework allows groups and projects to inherit settings values from ancestors (parent group on up the group hierarchy) and from instance-level application settings. The framework also allows settings values to be “locked” (enforced) on groups lower in the hierarchy.

Cascading settings historically have only been defined on ApplicationSetting, NamespaceSetting and ProjectSetting, though the framework may be extended to other objects in the future.

Add a new cascading setting to groups only

Settings are not cascading by default. To define a cascading setting, take the following steps:

1. In the NamespaceSetting model, define the new attribute using the cascading_attr helper method. You can use an array to define multiple attributes on a single line.

   class NamespaceSetting
     include CascadingNamespaceSettingAttribute
   
     cascading_attr :delayed_project_removal
   end
   

2. Create the database columns.

   You can use the following database migration helper for a completely new setting. The helper creates four columns, two each in namespace_settings and application_settings.

   class AddDelayedProjectRemovalCascadingSetting < Gitlab::Database::Migration[2.1]
     include Gitlab::Database::MigrationHelpers::CascadingNamespaceSettings
   
     def up
       add_cascading_namespace_setting :delayed_project_removal, :boolean, default: false, null: false
     end
   
     def down
      remove_cascading_namespace_setting :delayed_project_removal
     end
   end
   

   Existing settings being converted to a cascading setting will require individual migrations to add columns and change existing columns. Use the specifications below to create migrations as required:

   1. Columns in namespace_settings table:
      • delayed_project_removal: No default value. Null values allowed. Use any column type.
      • lock_delayed_project_removal: Boolean column. Default value is false. Null values not allowed.
   2. Columns in application_settings table:
      • delayed_project_removal: Type matching for the column created in namespace_settings. Set default value as desired. Null values not allowed.
      • lock_delayed_project_removal: Boolean column. Default value is false. Null values not allowed.

Convenience methods

By defining an attribute using the cascading_attr method, a number of convenience methods are automatically defined.

Definition:

cascading_attr :delayed_project_removal

Convenience Methods Available:

• delayed_project_removal
• delayed_project_removal=
• delayed_project_removal_locked?
• delayed_project_removal_locked_by_ancestor?
• delayed_project_removal_locked_by_application_setting?
• delayed_project_removal? (Boolean attributes only)
• delayed_project_removal_locked_ancestor (Returns locked namespace settings object [namespace_id])

Attribute reader method (delayed_project_removal)

The attribute reader method (delayed_project_removal) returns the correct cascaded value using the following criteria:

1. Returns the dirty value, if the attribute has changed. This allows standard Rails validators to be used on the attribute, though nil values must be allowed.
2. Return locked ancestor value.
3. Return locked instance-level application settings value.
4. Return this namespace’s attribute, if not nil.
5. Return value from nearest ancestor where value is not nil.
6. Return instance-level application setting.

_locked? method

By default, the _locked? method (delayed_project_removal_locked?) returns true if an ancestor of the group or application setting locks the attribute. It returns false when called from the group that locked the attribute.

When include_self: true is specified, it returns true when called from the group that locked the attribute. This would be relevant, for example, when checking if an attribute is locked from a project.

Add a new cascading setting to projects

Background

The first iteration of the cascading settings framework was for instance and group-level settings only.

Later on, there was a need to add this setting to projects as well. Projects in GitLab also have namespaces, so you might think it would be easy to extend the existing framework to projects by using the same column in the namespace_settings table that was added for the group-level setting. But, it made more sense to add cascading project settings to the project_settings table.

Why, you may ask? Well, because it turns out that:

• Every user, project, and group in GitLab belongs to a namespace
• Namespace has_one namespace_settings record
• When a group or user is created, its namespace + namespace settings are created via service objects (code).
• When a project is created, a namespace is created but no namespace settings are created.

In addition, we do not expose project-level namespace settings in the GitLab UI anywhere. Instead, we use project settings. One day, we hope to be able to use namespace settings for project settings. But today, it is easier to add project-level settings to the project_settings table.

Implementation

An example of adding a cascading setting to a project is in MR 149931.

Cascading setting values on write

The only cascading setting that actually cascades values at the database level in the new recommended way is duo_features_enabled. That setting cascades from groups to projects. Issue 505335 describes adding this cascading from the application level to groups as well.

Legacy cascading settings writes

In the first iteration of the cascading settings framework, the “cascade” was as the application code-level, not the database level. The way this works is that the setting value in the application_settings table has a default value. At the namespace_settings level, it does not. As a result, namespaces have a nil value at the databse level but “inherit” the application_settings value.

If the group is updated to have a new setting value, that takes precedent over the default value at the application_settings level. And, any subgroups will inherit the parent group’s setting value because they also have a nil value at the database level but inherit the parent value from the namespace_settings table. If one of the subgroups update the setting, however, then that overrides the parent group.

This introduces some potentially confusing logic.

If the setting value changes at the application_settings level:

• Any root-level groups that have the setting value set to nil will inherit the new value.
• Any root-level groups that have the setting value set to a value other than nil will not inherit the new value.

If the setting value changes at the namespace_settings level:

• Any subgroups or projects that have the setting value set to nil will inherit the new value from the parent group.
• Any subgroups or projects that have the setting value set to a value other than nil will not inherit the new value from the parent group.

Because the database-level values cannot be seen in the UI or by using the API (because those both show the inherited value), an instance or group admin may not understand which groups/projects inherit the value or not.

The exception to the inconsistent cascading behavior is if the setting is locked. This always “forces” inheritance.

In addition to the confusing logic, this also creates a performance problem whenever the value is read: if the settings value is queried for a deeply nested hierarchy, the settings value for the whole hierarchy may need to be read to know the setting value.

Recommendation for cascading settings writes going forward

To provide a clearer logic chain and improve performance, you should be adding default values to newly-added cascading settings and doing a write on all child objects in the hierarchy when the setting value is updated. This requires kicking off a job so that the update happens asynchronously. An example of how to do this is in MR 145876.

Cascading settings that were added previously still have default nil values and read the ancestor hierarchy to find inherited settings values. But to minimize confusion we should update those to cascade on write. Issue 483143 describes this maintenance task.

Display cascading settings on the frontend

There are a few Rails view helpers, HAML partials, and JavaScript functions that can be used to display a cascading setting on the frontend.

Rails view helpers

cascading_namespace_setting_locked?

Calls through to the _locked? method to check if the setting is locked.

HAML partials

_enforcement_checkbox.html.haml

Renders the enforcement checkbox.

_setting_checkbox.html.haml

Renders the label for a checkbox setting.

_setting_label_fieldset.html.haml

Renders the label for a fieldset setting.

_lock_tooltips.html.haml

Renders the mount element needed to initialize the JavaScript used to display the tooltip when hovering over the lock icon. This partial is only needed once per page.

JavaScript

initCascadingSettingsLockTooltips

Initializes the JavaScript needed to display the tooltip when hovering over the lock icon (). This function should be imported and called in the page-specific JavaScript.

Put it all together

-# app/views/groups/edit.html.haml

= render 'shared/namespaces/cascading_settings/lock_tooltips'

- delayed_project_removal_locked = cascading_namespace_setting_locked?(:delayed_project_removal, @group)
- merge_method_locked = cascading_namespace_setting_locked?(:merge_method, @group)

= form_for @group do |f|
  .form-group{ data: { testid: 'delayed-project-removal-form-group' } }
    = render 'shared/namespaces/cascading_settings/setting_checkbox', attribute: :delayed_project_removal,
        group: @group,
        form: f,
        setting_locked: delayed_project_removal_locked,
        settings_path_helper: -> (locked_ancestor) { edit_group_path(locked_ancestor, anchor: 'js-permissions-settings') },
        help_text: s_('Settings|Projects will be permanently deleted after a 7-day delay. Inherited by subgroups.') do
      = s_('Settings|Enable delayed project deletion')
    = render 'shared/namespaces/cascading_settings/enforcement_checkbox',
        attribute: :delayed_project_removal,
        group: @group,
        form: f,
        setting_locked: delayed_project_removal_locked

  %fieldset.form-group
    = render 'shared/namespaces/cascading_settings/setting_label_fieldset', attribute: :merge_method,
        group: @group,
        setting_locked: merge_method_locked,
        settings_path_helper: -> (locked_ancestor) { edit_group_path(locked_ancestor, anchor: 'js-permissions-settings') },
        help_text: s_('Settings|Determine what happens to the commit history when you merge a merge request.') do
      = s_('Settings|Merge method')

    .gl-form-radio.custom-control.custom-radio
      = f.gitlab_ui_radio_component :merge_method, :merge, s_('Settings|Merge commit'), help_text: s_('Settings|Every merge creates a merge commit.'), radio_options: { disabled: merge_method_locked }

    .gl-form-radio.custom-control.custom-radio
      = f.gitlab_ui_radio_component :merge_method, :rebase_merge, s_('Settings|Merge commit with semi-linear history'), help_text: s_('Settings|Every merge creates a merge commit.'), radio_options: { disabled: merge_method_locked }

    .gl-form-radio.custom-control.custom-radio
      = f.gitlab_ui_radio_component :merge_method, :ff, s_('Settings|Fast-forward merge'), help_text: s_('Settings|No merge commits are created.'), radio_options: { disabled: merge_method_locked }

    = render 'shared/namespaces/cascading_settings/enforcement_checkbox',
      attribute: :merge_method,
      group: @group,
      form: f,
      setting_locked: merge_method_locked

// app/assets/javascripts/pages/groups/edit/index.js

import { initCascadingSettingsLockTooltips } from '~/namespaces/cascading_settings';

initCascadingSettingsLockTooltips();

Vue

cascading_lock_icon.vue

Using Vue

1. In the your Ruby helper, you will need to call the following to send do your Vue component. Be sure to switch out :replace_attribute_here with your cascading attribute.

 # Example call from your Ruby helper  method for groups
 cascading_settings_data = cascading_namespace_settings_tooltip_data(:replace_attribute_here, @group, method(:edit_group_path))[:tooltip_data]

 # Example call from your Ruby helper  method for projects
cascading_settings_data = project_cascading_namespace_settings_tooltip_data(:duo_features_enabled, project, method(:edit_group_path)).to_json

1. From your Vue’s index.js file, be sure to convert the data into JSON and camel case format. This will make it easier to use in Vue.

let cascadingSettingsDataParsed;
try {
  cascadingSettingsDataParsed = convertObjectPropsToCamelCase(JSON.parse(cascadingSettingsData), {
    deep: true,
  });
} catch {
  cascadingSettingsDataParsed = null;
}

1. From your Vue component, either provide/inject or pass your cascadingSettingsDataParsed variable to the component. You will also want to have a helper method to not show the cascading-lock-icon component if the cascading data returned is either null or an empty object.

// ./ee/my_component.vue

<script>
export default {
  computed: {
    showCascadingIcon() {
      return (
        this.cascadingSettingsData &&
        Object.keys(this.cascadingSettingsData).length
      );
    },
  },
}
</script>

<template>
  <cascading-lock-icon
    v-if="showCascadingIcon"
    :is-locked-by-group-ancestor="cascadingSettingsData.lockedByAncestor"
    :is-locked-by-application-settings="cascadingSettingsData.lockedByApplicationSetting"
    :ancestor-namespace="cascadingSettingsData.ancestorNamespace"
    class="gl-ml-1"
  />
</template>

You can look into the following examples of MRs for implementing cascading_lock_icon.vue into other Vue components:

• Add cascading settings in Groups
• Add cascading settings in Projects

Reasoning for supporing both HAML and Vue

It is the goal to build all new frontend features in Vue and to eventually move away from building features in HAML. However there are still HAML frontend features that utilize cascading settings, so support will remain with initCascadingSettingsLockTooltips until those components have been migrated into Vue.