https://bugzilla.wikimedia.org/show_bug.cgi?id=41130

Bawolff (Brian Wolff) <[email protected]> changed:

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--- Comment #24 from Bawolff (Brian Wolff) <[email protected]> ---
(In reply to comment #18)
> I found a workaround to fix thumbnails affected by this I think. (though we
> should fix the root cause of course).
> 
> If I run /w/thumb.php?f=name.jpg&width= for the size in question, then I
> think
> this will force generation of a thumb (bypassing the cached copy). This
> causes
> a thumb file to be in the filesystem again, which makes the cached copy of
> this
> image purgeable..
> 
> 
> So thumb.php -> purge page -> purge browser cache

Wouldn't it be easier to view a url like
http://upload.wikimedia.org/wikipedia/commons/thumb/1/14/Button_base.svg/119px-Button_base.svg.png?someStuffAtEndToForceAPurgeMiss

which should force the backend to generate the image, and then do ?action=purge
on image description page.

Another case is https://upload.wikimedia.org/wikipedia/bcl/b/bc/Wiki.png
(provided you're in north america). Note: that's the full-sized version of the
image, so it should always be there in the backend, and ?action=purge on the
image description page seems to have no effect on its cached value.

>a) Change SquidPurgeClientPool to return some status info on run() that checks
>if any of the sockets where marked as "down" (got a non 200/404 message). Then
>change the squid purge code to be first, and to not purge anything in swift
>unless the squid purge succeeded. This would still be vulnerable to race
>conditions (you can purge afterwards again but have the same issue as before).

Unless I missed something, that's not an option unless we give up on the whole
multicast udp htcp thing.


----
Possibly related - I've looked at two specific instances of images not getting
purged out of squid cache. In both cases the image was purged if you were
visiting from europe, but not from N. America. The headers on the request to
North America seem to indicate that it was coming from varnish servers, and the
europe request from squid servers. I imagine there's a pretty good chance that
is coincidence, but thought I should mention that anyhow.



(In reply to comment #22)
> Some people here have reported this as seeming to happen for all of their
> uploads. Is it literally happening for handfuls of re-uploads in a row and
> for
> a large number of people? It would be helpful for more reports here. The bug
> were stale thumbnails can get stuck should still be rare, unless PURGE
> requests
> are failing all the time (sounds like an operations issue).

I think there might be significant issues with PURGE failings. see my comment
at bug 38879 comment 10

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