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WooCommerce: Controlling an Asset CDN

Continuing on from my last post, I faced a new issue when it came to adding products and the associated images I was putting in (from Cloudinary) was getting uploaded to the WordPress media library. Not only that, using the URL from my site instead of the CDN it had come from. Double up on all of my images, what a waste - and I want to host from the CDN to keep costs of bandwidth down.  So let me show you how I overcame it.

Separating the herd

What was interesting, is that it was keeping a record of the original source location, and I found I could filter these apart from the rest of my media library:


With this in mind, I wrote a function around it so I could use it to give me a true/false if the given attachment was from this source.


Attaching the hook

Next, needed a way that as soon as an image was added, that it would update the attachment (post) pointing to the correct reference, and not to the file on our server. I found the add_attachment hook, which fires only when an image is added.  So I made the following function which not only updates the item to the external URL, but also deletes the file off our server:

It appears we are moving with steam - but somehow the URL persists to be from our server, only this time the file is not found, be we had deleted it.  So we need to alter the logic WordPress is using to resolve the domain and path.  I found the filter wp_get_attachment_url, which provided this cure:


Final cleanse

Short and sweet. But hang on? Large images are now ok, correctly coming from our CDN, but our thumbnails are not?  Generally, with WordPress generating thumbnails, this is a good thing, but in this case it was not desired.  Here, the system attempts to put together the path of the URL, along with the file it would had generated previously when it was uploaded, but our aim now is to keep that clean and only point to the original URL.

The information for these filename and image properties lives in a serialized wp_attachment_metadata key in the wp_postsmeta table.  With time against me, I've taken the quick and nasty (but still clean) method of renaming all sizes for each thumbnail:


As you can see, this pulled me through quite a re-factor, but all problems were solved.

Preventative cure

There is one more thing needed to be implemented to tie things down.  It appears WooCommerce has a background task of attempting to re-generate thumbnails, likely if they are missing.  Fortunately, I quickly came across this small tip:


And that's it!  I hope this helped any of you facing the same hurdles.

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