Question

Flarum core integrates with the filesystem to store and serve assets (like compiled JS/CSS or upload logos/favicons) and avatars.

Extensions can use Flarum's provided utils for their own filesystem interaction and file storage needs. This system is based around Laravel's filesystem tools, which are in turn based on the Flysystem library.

Filesystem disks represent storage locations, and are backed by storage drivers, which we'll cover later. Flarum core has 2 disks: flarum-assets and flarum-avatars.

To access a disk, you'll need to retrieve it from the Filesystem Factory. To do so, you should inject the factory contract in your class, and access the disks you need.

Let's take a look at core's DeleteLogoController for an example:

<?php


/*
 * This file is part of Flarum.
 *
 * For detailed copyright and license information, please view the
 * LICENSE file that was distributed with this source code.
 */


namespace Flarum\Api\Controller;


use Flarum\Http\RequestUtil;
use Flarum\Settings\SettingsRepositoryInterface;
use Illuminate\Contracts\Filesystem\Factory;
use Illuminate\Contracts\Filesystem\Filesystem;
use Laminas\Diactoros\Response\EmptyResponse;
use Psr\Http\Message\ServerRequestInterface;


class DeleteLogoController extends AbstractDeleteController
{
    /**
     * @var SettingsRepositoryInterface
     */
    protected $settings;


    /**
     * @var Filesystem
     */
    protected $uploadDir;


    /**
     * @param SettingsRepositoryInterface $settings
     * @param Factory $filesystemFactory
     */
    public function __construct(SettingsRepositoryInterface $settings, Factory $filesystemFactory)
    {
        $this->settings = $settings;
        $this->uploadDir = $filesystemFactory->disk('flarum-assets');
    }


    /**
     * {@inheritdoc}
     */
    protected function delete(ServerRequestInterface $request)
    {
        RequestUtil::getActor($request)->assertAdmin();


        $path = $this->settings->get('logo_path');


        $this->settings->set('logo_path', null);


        if ($this->uploadDir->exists($path)) {
            $this->uploadDir->delete($path);
        }


        return new EmptyResponse(204);
    }
}

The object returned by $filesystemFactory->disk(DISK_NAME) implements the Illuminate\Contracts\Filesystem\Cloud interface, and can be used to create/get/move/delete files, and to get the URL to a resource.

Some extensions will want to group their resources / uploads onto a custom disk as opposed to using flarum-assets or flarum-avatars.

This can be done via the Filesystem extender:

use Flarum\Extend;


return [
    (new Extend\Filesystem)
        ->disk('flarum-uploads', function (Paths $paths, UrlGenerator $url) {
            return [
                'root'   => "$paths->public/assets/uploads",
                'url'    => $url->to('forum')->path('assets/uploads')
            ];
        });

Since all disks use the local filesystem by default, you'll need to provide a base path and base URL for the local filesystem.

The config array can contain other entries supported by Laravel disk config arrays. The driver key should not be provided, and will be ignored.

Flarum selects the active driver for each disk by checking the disk_driver.DISK_NAME key in the settings repository and config.php file. If no driver is configured, or the configured driver is unavailable, Flarum will default to the local driver.

You can define new storage drivers by implementing the Flarum\Filesystem\DriverInterface interface, and registering it via the Filesystem extender:

use Flarum\Extend;


return [
    (new Extend\Filesystem)
        ->driver('aws-with-cdn', AwsWithCdnDriver::class);

Filesystem storage drivers are a very powerful tool that allows you to completely customize file storage locations, attach arbitrary CDNs, and otherwise extend the filesystem / cloud storage integration layer.

danger

Some drivers might try to index their filesystem every time the driver is instantiated, even if only the url method is needed. This can have serious performance implications. In most cases, you'll want to ensure that your driver's url method does not ping the remote filesystem. Similarly, the remote filesystem should usually not be accessed until operations are actually executed.

Flarum does not currently provide a GUI for selecting drivers for disks, or for entering settings for drivers. This might be added in the future. For now, extensions are responsible for providing a GUI for their disks and drivers.

As noted above, if your extension provides a GUI for selecting drivers for a disk, it should modify the disk_driver.DISK_NAME key in settings.