Hi Everyone,
Next week we're going to switch the back end system that hosts thumbnail[1]
images. We have been using
ms5<http://ganglia.wikimedia.org/latest/?r=day&cs=&ce=&m=&am…
Sun server running linux) to serve all thumbnails. We are switching
to Openstack
Swift <http://wikitech.wikimedia.org/view/Swift>, a clustered object
store. Though we have done testing and expect no problems, I want to
publicize the change so that if issues do appear, they are quickly directed
to the right place.
Here's the schedule:
* Monday Feb 6th: move 0.4% of all thumbnail traffic from ms5 to swift.
Only thumbnails with "/thumb/a/a2/"[2] in the URL will be affected.
* Tuesday: move 12.5% of traffic - thumbnails with "/thumb/a/" or
"/thumb/b/" will be affected
* Wednesday: move 50% of traffic - thumbnails with "/thumb/(a-f or 0 or
1)/" will be affected
* Thundlay: move 100% of traffic - all thumbnails will be served from Swift
Potential symptoms that might be related to this change on Monday:
* a thumbnail image with /a/a2/ simply fails to load
** try changing the number preceding 'px' to generate a different size
image[3]
* you delete an image and the thumbnail is still available
** try purging the cache[4] and see if that makes it go away
** try changing the number preceding 'px' and see what happens
* you move an image to a new name and it's still available at the old name,
when either the new or old name has /a/a2/ in the URL
** please provide full URLs for both the new and old names
If any of these things happen, or if something else odd happens with images
or thumbnails and you feel it might be related, please join #wikimedia-tech
in IRC and ping me (maplebed) or Aaron (AaronSchulz). If neither of us are
available or you would prefer to just leave us a message, add a note to
https://www.mediawiki.org/wiki/SwiftMedia/Issues. :) If things are
severely broken, you can ask someone in the #wikimedia-tech to page me.
Thanks for your help!
-ben
[1] In case you don't know what I mean by thumbnail images, I'm talking
about all URLs that start
http://upload.wikimedia.org/ and have /thumb/ in
the path. When an image is uploaded to a wiki (or commons), Mediawiki
automatically generates scaled versions of the image. These are what I
call 'thumbnails'. Nearly every time an image is used in a wiki page it is
actually a thumbnail being used. Try going to any wiki page with an image,
right click on the image, and choose 'view image'. You'll get something
like
http://upload.wikimedia.org/wikipedia/commons/thumb/4/45/Liberty_Head_Nicke…
as the URL (this was taken from enwiki's featured article today)
[2] For example,
http://upload.wikimedia.org/wikipedia/commons*/thumb/a/a2/*Little_kitten_.j…
[6]
[3] For example,
http://upload.wikimedia.org/wikipedia/commons/thumb/a/a2/Little_kitten_.jpg/
*799px*-Little_kitten_.jpg
[4] Find the URL for the main image file (rearrange the URL to find the
original image - /wikipedia/commons ->
commons.wikipedia.org) and add
"?action=purge" to the end of the URL (eg
http://commons.wikimedia.org/wiki/File:Little_kitten_.jpg?action=purge
[5] Image in the public domain
[6] cc-by 3.0,
Alexanderwdark<http://commons.wikimedia.org/w/index.php?title=User:Alexa…
