README.md

Feature flag

You can now define feature flags in environment global variables or database.

How to use it?

You can use feature flag to easily switch off/on parts of TAO functionality.

IMPORTANT: It is recommended to use an external cache (i.e redis) instead of phpfile to avoid the need to restart the server after saving a feature flag.

Usage to save a feature flag:

php index.php 'oat\tao\scripts\tools\FeatureFlag\FeatureFlagTool' -s FEATURE_FLAG_EXAMPLE -v true

Usage to get feature flag report:

php index.php 'oat\tao\scripts\tools\FeatureFlag\FeatureFlagTool' -r true

Usage to get info about feature flag

php index.php 'oat\tao\scripts\tools\FeatureFlag\FeatureFlagTool' -i FEATURE_FLAG_EXAMPLE

Clear feature flag cache

Only available for DB feature flags

php index.php 'oat\tao\scripts\tools\FeatureFlag\FeatureFlagTool' -cc true

Feature flag naming standard

It is import tht we will use FEATURE_FLAG_ prefix for our feature flags to recognise them and their purpose.

AbstractFeatureFlagFormPropertyMapper

To hide/show form fields you can extend AbstractFeatureFlagFormPropertyMapper with your configurable service that has OPTION_FEATURE_FLAG_FORM_FIELDS mapped to list of fields that you want to hide/show.

<?php
use oat\taoLti\models\classes\LtiProvider\FeatureFlagFormPropertyMapper;    

return new FeatureFlagFormPropertyMapper(
    [
        FeatureFlagFormPropertyMapper::OPTION_FEATURE_FLAG_FORM_FIELDS => [
                'formField_01' => [
                    'FEATURE_FLAG_NAME'
                ]
            ]
    ]
);

This configuration will display formField_01 when FEATURE_FLAG_NAME is enabled

SectionVisibilityFilterInterface

tao/SectionVisibilityFilter is responsible for listing sections that can be disabled from user. In order to add more sections that have to be disabled/enabled based on feature flag.

<?php

return new oat\tao\model\menu\SectionVisibilityFilter(array(
    'featureFlagSections' => [
        'sectionName1' => [
            'FEATURE_FLAG_01'
        ],
        'sectionName2/actionName' => [
            'FEATURE_FLAG_01'
        ]
    ],
    'featureFlagSectionsToHide' => [
        'sectionNameToHide1' => [
            'FEATURE_FLAG_02'
        ],
        'sectionNameToHide2/actionName' => [
            'FEATURE_FLAG_02'
        ]
    ]
));

This configuration will display sectionName1 when FEATURE_FLAG_01 is enabled. This configuration will display actionName from sectionName2 when FEATURE_FLAG_01 is enabled. This configuration will hide sectionNameToHide when FEATURE_FLAG_02 is enabled. This configuration will display actionName from sectionNameToHide when FEATURE_FLAG_02 is enabled.

Override configs on execution time

These feature helps to dynamically overrride configs according to a featureFlag and therefore, no need for redeployment or server restart.

This is done though the FeatureFlagConfigSwitcher and composition with FeatureFlagConfigHandlerInterface by following the steps bellow:

1. Create a handler implementing FeatureFlagConfigHandlerInterface.

Example:

declare(strict_types=1);

use oat\tao\model\featureFlag\FeatureFlagCheckerInterface;
use oat\tao\model\featureFlag\FeatureFlagConfigHandlerInterface;

class MyClientConfigHandler implements FeatureFlagConfigHandlerInterface
{
    /** @var FeatureFlagCheckerInterface */
    private $featureFlagChecker;

    public function __invoke(array $configs): array
    {
        if ($this->featureFlagChecker->isEnabled('FEATURE_FLAG_EXAMPLE')) {
            //change the config
        }      
        
        //... apply another config changes if required

        return $configs;
    }
}

2. Call the handler in your DI container definition.

use oat\generis\model\DependencyInjection\ContainerServiceProviderInterface;
use oat\tao\model\featureFlag\FeatureFlagConfigSwitcher;
use Symfony\Component\DependencyInjection\Loader\Configurator\ContainerConfigurator;

class MyDIContainerServiceProvider implements ContainerServiceProviderInterface
{
    public function __invoke(ContainerConfigurator $configurator): void
    {
        $services->get(FeatureFlagConfigSwitcher::class)
            ->call(
                'addClientConfigHandler',
                [
                    MyClientConfigHandler::class,
                ]
            )->call(
                'addExtensionConfigHandler',
                [
                    'taoQtiItem',
                    'qtiCreator',
                    MyExtensionConfigHandler::class
                ]
            );
    }
}

We currently support 2 types of configuration override on FeatureFlagConfigSwitcher.

• The ones stored on client_lib_config_registry.conf.php, including featureVisibility.
• The extension/module based ones.

use oat\tao\model\featureFlag\FeatureFlagConfigSwitcher;

/** @var FeatureFlagConfigSwitcher $featureFlagConfigSwitcher */
$featureFlagConfigSwitcher; // Get from DI container...

$configs = $featureFlagConfigSwitcher->getSwitchedExtensionConfig('taoQtiItem', 'qtiCreator'); // Config from extension
$configs = $featureFlagConfigSwitcher->getSwitchedClientConfig(); // Config from client_lib_config_registry.conf.php