https://bugzilla.wikimedia.org/show_bug.cgi?id=49118
Faidon Liambotis <fai...@wikimedia.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|RESOLVED |REOPENED
Resolution|FIXED |---
--- Comment #3 from Faidon Liambotis <fai...@wikimedia.org> ---
The patchset is a good first step, but I don't think it's enough.
First of all, if I'm reading the code right, the attempt key is keyed by
original _and_ thumb size; my impression is that almost always, scaling errors
are because of properties of the original file, not the thumb size specifically
(very large, like the 100MB TIFFs, or very complex, like the animated DNA
helix). I think that it'd be better to just count hits with just the original,
as otherwise we are getting DoSed by people hitting the same image in different
pages, e.g. Special:NewFiles' 120px vs. Special:ListFiles' 180px.
More importantly, the code seems to add a key in memcache with TTL 3600. This
won't actually fix the effect that the /tmp listing presented in the original
description, since those images were apart hours, or even days from each other.
It will also not protect us from the general issue of "unscalable images",
images that we can never render with our current thresholds but we will forever
try to (hundreds of megabytes old multipage TIFFs, for instance).
I think a short memcached-based approach is fine for short temporary errors,
like protecting us from bursts, but my original thought -and one that would
probably save us from today's recurring rendering outages- would be to actually
store this in a flag the image table in the database and *never* try again,
unless the flag is reset by an admin or the epoch is bumped. The flag could
even be set to the current date, as to be able to quickly reset it with a
query, if our infrastructure goes nuts for a day and we get flooded with false
positives.
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