Clearing PHP Apcu cache on Cloud Classic

Issue

I need to clear APCu cache on Cloud Classic.

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/