I'm sorry but I cannot write down the full documentation of reaction caching. This is not as you're trying to imagine or explain. The number of reaction cache files is equal to the number of cached posts so it doesn't matter how many reactions you get per day and this doesn't make the reaction faster, instead it makes the whole forum faster starting from topic and post loading time.

Even the empty cache file makes one query less saying there is no reaction. So when posts re loaded they should not check in the database for reactions. This is all I'd explain about the reaction cache. Again if you have file limitation on your hosting you can disable the reaction cache as I instructed above.

This is where some of my confusion lies because my forums might be getting 10 Likes/Dislikes a day but Im generating 10s of thousands of /reaction cache files -- nearly all of them empty. 

The same can be said for the other cache directories where many of the files just have what appear to be garbage null strings in them and not any relevant data. This is why a large portion of the cache files are 6 bytes.

Some of the topic and post cache files do have referencing forum data in them and are legitimate.

What is the purge/expiration lifecycle on the cache directories?

There are more than ten type of caches in wpForo, they are being auto-purged for sure:

1. forum / single
2. forum / list
3. topic / single
4. topic / list
5. post / single
6. post / list
7. member / single
8. member / list
9. tags
10. avatars
11. urls
12. options
13. reactions

Only one of them, the reactions type, is not being auto-purged. They will be deleted if the reacted post is deleted. So this type of cache stores likes/dislikes and other reactions of each post, making the performance dozens of time higher if you have hundreds of thousands reactions. Sometimes forums have millions of reactions, each post may have dozens or hundreds of reactions, so you may have tens of thousands of reactions cache files, but they will make your forum very fast. 

https://wpforo.com/community/postid/116761/

Thank you for this solution, after following your advice it has now allowed me to run with caching re-enabled 👍 I have now quadrupled my previous number of free file allocations.

Is there purging process of these files or do they create in perpetuity without any automated cleanup? 

When creating a backup archive of the entire node (web site) I will probably exclude these folders.

https://wpforo.com/community/postid/116761/

It looks like that around 150000 files are coming from /home/mydomain/public_html/wp-content/uploads/wpforo/cache/item directory, more specifically, its subdirectories: ---

110416 ./reaction

34240 ./url

6399 ./topic

3357 ./avatar

Hi @udpride,

Cache files allow you to have many times better performance and keep small amount of requests to the database. Please note that running a not-small forum on a shared hosting is not a good idea.

1. Shared Hosting: Shared hosting providers limit the number of files (also known as inodes) you can have. This can range from 100,000 to 500,000 files, depending on the provider and plan. So if yours allows 200k files then this is one of the bad shared hosting service.

2. VPS (Virtual Private Server): On a VPS, the number of files is generally limited by the amount of disk space.

3. Dedicated Hosting: With dedicated hosting, there are no specific limits on the number of files as well.

4. Cloud Hosting: Cloud hosting often offers more flexibility and there are no limits as well.

However you can still use your shared hosting service by disabling the reactions and URL cache. It's the 90% of all your cache files. Just use Code Snippets plugin to add this code or add this code directly in the functions.php of your child theme:

add_filter('wpforo_cache_url', '__return_false' );
add_filter('wpforo_cache_avatar', '__return_false' );
add_filter('wpforo_cache_reaction', '__return_false' );

Then use your FTP client or some File Manager plugin to delete the /cache folder in this directory:

wp-content/uploads/wpforo/

The /cache folder will be re-created by wpForo for topic and posts caches, but the number of those files will be small.