Historically, we've allowed clients to request image thumbnails of arbitrary size and relied on live-rendering those and then storing them in a cache.
This is not really sustainable long term, and we want, in the context of responsible use of our resources, to limit the ability of clients to generate arbitrary thumbnails sizes.
To this end, we want to do the following:
- Compile a complete list of all the "canonical" thumbnail sizes, including the ones we show on the commons file pages, the ones we pre-generate, and the ones used on-wiki (T408715)
- Measure the frequency of use of thumbnail sizes, including canonical and popular non-canonical ones (T410304)
- Drop seldomly used sizes from this list; also rationalize the pre-generation list (T412971)
- Start rate-limiting generation of thumbnails at sizes different from the canonical ones. (cf. T402792 )
- [Stretch] Block non-standard sized requests from untrusted, suspect-bot traffic
Follow-up work on moving to only serve standard-size thumbnails is going to be done under WE 5.4.10 - T414805