Redis and Formidable Pro not working together

so I worked with their support to resolve it and apparently there is a issue with the WP_Object_Cache::set() function?

Can you link to where you had this conversation, or ask them to weigh in with the technical details on this thread?

When I deactivated Pantheon’s Redis and the WordPress plugin and deleted the additional file that the Pantheon instructions guided me to do, Formidable now is working but now I can’t use Redis. Is there a work around?

If it’s a genuine bug, then we should fix the bug and then you’ll be able to use WP Redis.

Hi Daniel,

Here is Jamie from Formidable Pro support’s entire email:

Permalink:
https://formidablepro.com/help-desk/deleting-multiple-entries/#comment-305229
From: Jamie

Post:
Thank you for letting me check this out. Something on your site is
affecting the wp_cache_set function. Could you check with your webhost
to see if they have anything that affects the wp_cache_set function or
the WP_Object_Cache::set() function?

If they are modifying the wp_cache_set or WP_Object_Cache::set()
functions, could you request that this be turned off on your site? You
could let them know that other plugins are dependent on these core
WordPress functions and when they are modified, it causes issues for
these plugins.

Also, I just want to add some notes for myself to help me remember
what the issue was.
– The expected index in the $wp_object_cache is [ $group ] but it was
actually [ $group . $key ] on this site.
– Expected index: frm_actions
– Actual index:
frm_actions:a:7:{s:9:”post_type”;s:16:”frm_form_actions”;s:11:”post_status”;s:3:”any”;s:11:”numberposts”;i:99;s:7:”orderby”;s:5:”title”;s:5:”order”;s:3:”ASC”;s:10:”menu_order”;i:49;s:16:”suppress_filters”;b:0;}_type_email
– This modification of the typical format prevents the clear_cache
function from working as expected. Also, this will still retrieve the
incorrectly formatted cached data:
$results = wp_cache_get( $key, $group);
It’s possible that wp_cache_get is being modified as well.

This is an autogenerated message. Please do not reply directly to this
email.

I took a look at the Formidable Forms WordPress plugin. Unfortunately, it appears the plugin is incompatible with object cache drop-ins because of the way it works (incorrectly) with the WordPress object cache.

If you’d like to send this thread to their developers, I’d be happy to offer some pointers on how they can make their plugin more compatible with object cache drop-ins.

Hi Daniel,
I sent along your message to Steph Wells of Formidable Pro and they would be happy to understand what they need to do to make the object cache work. Would you mind if I sent them information to get in touch with you?

Dave

Would you mind if I sent them information to get in touch with you?

Sure — my email address is in my Github profile: https://github.com/danielbachhuber

For the next person to run into this, here’s my diagnosis:

Under the hood, WP Redis acts as an interface between WordPress and Redis (example). The references to _call_redis() make a request to Redis to either get, set, or delete cache data. Notably, because Redis is a key=>value persistent storage engine, WP Redis concatenates the cache key and group into one key (reference). Other object cache drop-ins employ a similar approach (WordPress PECL Memcached drop-in).

Formidable is doing everything right, except there’s a bit of grey area in how groups should be treated. To delete all cache data for a group, Formidable iterates through $wp_object_cache->cache (reference). The immediate problem is that the object cache drop-ins concatenate the key and the group into a single cache key, meaning it isn’t stored in a format Formidable expects. The more conceptual problem is that object cache drop-ins lazy-load data into the $wp_object_cache global as it’s requested. *Meaning* cache_delete_group() won’t reliably delete all group data, because an unknown amount of group data is still stored in the persistent storage backend.

Daniel,
Thank you for working through this. This is out of my league.
Dave