When I got the warning that the apc.shm_size is almost full It took me a long time to figure out how to cleanly fix it in docker and where the config PHP is stored.
It feels a bit odd to me that a setting that the docs recommend to change requires me to figure out where the PHP config dir is and add a file to it.
I would suggest adding a PHP_APC_SHM_SIZE environment variable similar to PHP_UPLOAD_LIMIT.