When requesting random images from Commons' MediaWiki API and requesting a thumbnail for it, I often get a HTTP 500.
<html><head><title>Error generating thumbnail</title></head>
<h1>Error generating thumbnail</h1>
Error creating thumbnail:
<!-- http://commons.wikimedia.org/w/thumb_handler.php/f/fb/USMC-05934.jpg/400px-USMC-05934.jpg -->
<!-- mw1154 -->
Usually when trying again, it just works.
I've been getting these errors in many different environments:
- When reading articles and HiDPI plugin swaps the src attributes (the larger version would fail maybe)
- When opening the VisualEditor (rendering the new DOM means we re-parse the <img>tag and thus re-request it, thus making it more likely for the error to happen again)
- When working with gadgets that render image galleries through requesting file category members and the thumbnail url.
I don't think the scenario is relevant, there is either something wrong with the thumbnail generator script that is triggered by lots of images. Or there is a few faulty servers in the upload.wikimedia.org pool that cause the errors.