Issue¶

I need to clear APCu cache.

Resolution¶

First, try drush cr to rebuild all the caches. It's rare that you actually need to clear APCu cache separately.

APCu is a very small cache, usually 32M, and it's just for the PHP Caches that were previously a part of APC, and are now User Cache see https://www.php.net/manual/en/book.apcu.php for more information. 

• Place a script you can call via HTTP that calls apcu_clear_cache()
• Request it twice in the web browser following the process outlined in https://www.drupal.org/node/2752961

Each time, you will need to specify the instance to load on each request by adding a ah_app_server=ded-20746 or ah_app_server=ded-20747 cookie.

Example code of the PHP apcu_clear_cache() script 

<?php
echo "APC-User cache: " .  apcu_clear_cache ( ). "\n";

This function always returns true. It's a little confusing.

This can also be helpful to monitor and tune APCu cache: https://anavarre.net/how-to-monitor-and-tune-apcu/