I like that idea. Thanks, Gergo!

On Thu, Aug 14, 2014 at 2:41 AM, Gergo Tisza <[email protected]> wrote:

> On Wed, Aug 13, 2014 at 10:36 AM, Gilles Dubuc <[email protected]>
> wrote:
>
>> Currently the file page provides a set of different image sizes for the
>> user to directly access. These sizes are usually width-based. However, for
>> tall images they are height-based. The thumbnail urls, which are used to
>> generate them pass only a width.
>>
>> What this means is that tall images end up with arbitrary thumbnail
>> widths that don't follow the set of sizes meant for the file page. The end
>> result from an ops perspective is that we end up with very diverse widths
>> for thumbnails. Not a problem in itself, but the exposure of these
>> random-ish widths on the file page means that we can't set a different
>> caching policy for non-standard widths without affecting the images linked
>> from the file page.
>>
>> I see two solutions to this problem, if we want to introduce different
>> caching tiers for thumbnail sizes that come from mediawiki and thumbnail
>> sizes that were requested by other things.
>>
>> The first one would be to always keep the size progression on the file
>> page width-bound, even for soft-rotated images. The first drawback of this
>> is that for very skinny/very wide images the file size progression between
>> the sizes could become steep. The second drawback is that we'd often offer
>> less size options, because they'd be based on the smallest dimension.
>>
>> The second option would be to change the syntax of the thumbnail urls in
>> order to allow height constraint. This is a pretty scary change.
>>
>> If we don't do anything, it simply means that we'll have to apply the
>> same caching policy to every size smaller than 1280. We could already save
>> quite a bit of storage space by evicting non-standard sizes larger than
>> that, but sizes lower than 1280 would have to stay the way they are now.
>>
>> Thoughts?
>>
>
> A workaround would be to add an extra parameter to height-constrained
> images, such as 623px-heightconstrained-Foo.png (as far as I can see, this
> is a non-scary change), and not purge files which have this parameter. A
> bit messy, but if the purging itself is also a temporary workaround until
> we have a new storage mechanism with proper usage-based cache eviction,
> there is no point messing with fundamentals of the thumbnail url syntax.
>
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