Some but not all of the squid caches seem to be serving stale versions of both
thumbnails and original images. Purging or reuploading does not seem to help.
I have personally only encountered this problem with SVG images so far, but I
expect it probably affects all images.
See for example [[Wikipedia talk:WikiProject Mathematics/Graphics#Blank thumb in
svg?]]: the image
http://upload.wikimedia.org/wikipedia/en/thumb/0/05/Paley13.svg/200px-Paley13.svg.png
shows up for me as an old, blank version, while the 201-pixel thumb shows up
just fine. The HTTP response headers I get for the affected thumbnail are:
Connection: close
Date: Sat, 04 Nov 2006 20:12:44 GMT
Via: 1.0 sq6.pmtpa.wmnet:80 (squid/2.6.STABLE3), 1.0 sq12.wikimedia.org:80
(squid/2.6.STABLE4), 1.0 ragweed.knams.wikimedia.org:80 (squid/2.6.STABLE5), 1.0
vandale.knams.wikimedia.org:80 (squid/2.6.STABLE3)
Age: 2618
Server: lighttpd/1.4.13
Content-Length: 271
Content-Type: image/png
Client-Date: Sat, 04 Nov 2006 20:55:41 GMT
Client-Peer: 145.97.39.156:80
Client-Response-Num: 1
X-Cache: HIT from sq6.pmtpa.wmnet
X-Cache: MISS from sq12.wikimedia.org
X-Cache: HIT from ragweed.knams.wikimedia.org
X-Cache: MISS from vandale.knams.wikimedia.org
X-Cache-Lookup: HIT from sq6.pmtpa.wmnet:80
X-Cache-Lookup: MISS from sq12.wikimedia.org:80
X-Cache-Lookup: HIT from ragweed.knams.wikimedia.org:80
X-Cache-Lookup: MISS from vandale.knams.wikimedia.org:80
X-Powered-By: PHP/5.1.4
whereas the headers for the seemingly unaffected 201-pixel thumbnail are:
Connection: close
Date: Sat, 04 Nov 2006 19:59:07 GMT
Via: 1.0 sq7.pmtpa.wmnet:80 (squid/2.6.STABLE3), 1.0 sq12.wikimedia.org:80
(squid/2.6.STABLE4), 1.0 ragweed.knams.wikimedia.org:80 (squid/2.6.STABLE5)
Age: 3452
Server: lighttpd/1.4.13
Content-Type: image/png
Client-Date: Sat, 04 Nov 2006 20:55:57 GMT
Client-Peer: 145.97.39.156:80
Client-Response-Num: 1
X-Cache: HIT from sq7.pmtpa.wmnet
X-Cache: MISS from sq12.wikimedia.org
X-Cache: HIT from ragweed.knams.wikimedia.org
X-Cache-Lookup: HIT from sq7.pmtpa.wmnet:80
X-Cache-Lookup: MISS from sq12.wikimedia.org:80
X-Cache-Lookup: HIT from ragweed.knams.wikimedia.org:80
X-Powered-By: PHP/5.1.4
Of course, it's possible the both thumbs are affected, but the latter one just
happens to have been generated after the original image was fixed, and thus does
not appear blank.
Version: unspecified
Severity: normal
URL: http://en.wikipedia.org/wiki/Wikipedia_talk:WikiProject_Mathematics/Graphics#Blank_thumb_in_svg.3F