On Wed, Apr 9, 2014 at 6:29 PM, Brian Wolff <[email protected]> wrote:

> If you know the exact url of the api request, you can purge it on specific
> events (e.g. edits to a file page). But you need to know the precise url.
>
That's just sad... I was assuming Varnish supports some sort of tag-based
invalidation, but apparently you have to pay for that [1].

It might be easier then to add a cache-breaking parameter to the API
request URLs (something like the last file / file page modification date),
and store that in the HTML. At least there is a sane invalidation mechanism
for HTML pages. This would mean HTML pages needed to be invalidated when a
new file is uploaded or the file page is edited, which sounds hard
(cross-wiki invalidations, ugh) but not impossible. I assume something like
that already exists for file uploads since the thumbnail URL might
potentially change as a result.

Per the IRC discussion with Gilles, we should start caching filerepoinfo,
userinfo, imageusage and globalusage right now, that's an easy win.
Filerepoinfo and userinfo (gender) don't change much, imageusage and
globalusage can, but meh, they are not very useful anyway, we only show the
first three entries. Coming up with some sort of caching mechanism for
imageinfo would be great, but sounds like an epic task.


[1]
https://www.varnish-software.com/blog/advanced-cache-invalidation-strategies
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