[Magento 2] How to clean the cache by TAG

Cleaning the cache by TAG is quite easy in Magento 2. You will need to:

• Inject the classes in your construct function
• Know the exact tags you want to cache
• Flush the actual Cache

Start creating your class injecting the classes we need:

use Magento\Backend\App\Action\Context;
use Magento\Framework\App\CacheInterface;

class YourClass extends AnyClass
   /**
     * @var CacheInterface
     */
    protected $cacheManager;    

    public function __construct(
        Context $context,
        CacheInterface $cacheManager
    ) {
        parent::__construct($context);
        $this->cacheManager = $cacheManager;
    }

Create a function to retrieve the tags you want to flush. For example, for a CMS page with an ID 2:

    /**
     * Return cache tags to flush
     *
     * @return array
     */
    public function getCacheTags()
    {
        return [\Magento\Cms\Model\Page::CACHE_TAG . '_2'];
    }

And, in a custom function you can just execute the cache cleaning with:

$this->cacheManager->clean($this->getCacheTags());

Important note: As I have experienced myself, if you use Varnish, this command won’t flush the varnish cache for that page. I’ve created the following question in StackExchange to see if someone can help.