Using the Drupal Cache API for Drupal Entity Caching

Question

I am reading up on the Cache API, and have a question about caching users (or objects in general) in the DB, i.e. the cache_default MySQL table.

Please consider the following simple function to retrieve a User object (I know this type of code should probably live in a custom service, but am using a function here, just for clarity):

<?php 

/** 
 * Get a user object
 * @param Integer
 * @return User 
 */
function get_user_data($uid)
{
    if ($uid) {
        $cache_id = 'my_user:' . $uid;
        $user = NULL;
        if ($cache = \Drupal::cache()->get($cache_id)) {
            // Read user object from the default cache.
            $user = $cache->data; 
        }
        else {
            // user not found in the cache.
            $user = \Drupal\user\Entity\User::load($uid);

            // Cache tags from User object, to tell Drupal to invalidate the cache
            // data after any change to the user.
            $user_cache_tags = $user->getCacheTags();

            // Store a serialized user object in the default cache.
            \Drupal::cache()->set($cache_id, $user, Cache::PERMANENT, $user_cache_tags);
        }
        return $user; 
    }

    return FALSE;
}

My goal is to cache a Drupal User object, that also depends on large amounts of data in multiple profiles (using the Profiles module).

The User for my use case might actually require more properties, or some way to an interface with Profile objects, and thus may need to extend User (a "MyUser" class etc), but the design of our objects is out of scope for this question.

My question is:

Does the above code accomplish anything useful? (Or Is Drupal already caching User objects somewhere, and the above code accomplishes nothing?)

Also assume for my use case:

I am not able to use Redis or Memcached.
My Drupal application must rely on many very cumbersome database queries (to read user tables, profile tables) every time I need to gather user data.

Thank you in advance.

Interesting question... I did find this issue that reports entity cache was added to core in D8 — 2pha
– 2pha, Commented Mar 12, 2024 at 23:55

David Fiaty · Accepted Answer · 2024-05-21 19:33:03Z

0

Yes, custom caching can be useful and comes on top of the core caching system. Drupal has a default strategy for caching. But using contexts, tags and age, you can fine tune the caching strategy to fit your needs.

You don't have to, but it's there if needed. Just like Drupal itself comes with a default setup, but allows fine tuning to fit specific needs.

However, caution is required when dealing with user data. Caching user data that doesn't depend on a state is fine. But state data should not be cached, as you will want both the user and your app to see changes instantly.

For example, you probably won't want the information on the login status of the user to be cached.

Have a look here: https://www.drupal.org/docs/8/api/cache-api/cache-api

edited May 21, 2024 at 19:33

answered May 21, 2024 at 19:23

David Fiaty

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