https://bugzilla.wikimedia.org/show_bug.cgi?id=41130
--- Comment #15 from Derk-Jan Hartman <[email protected]> 2012-10-25 13:34:54 UTC --- @TMg purging sometimes fails, because cache purging is a fire and forget system. It is too resource intensive to request confirmation for every single 'purge' request sent to every single caching server. If the squid/varnish that has been sent the purge request, never receives the request (lost UDP packet, dropped connection between america and europe, or stray electron), then it will never know it was supposed to purge it. Now the problem here is that when this has happened, we no longer have an accurate list anymore ( the thumbnails have disappeared from the filesystem) of what we NEED to purge. This combined with the problem that you cannot create 'wildcard' requests on squid (or varnish) because they don't store the original urls, just unique hashes of those urls, causes the problems that we see. There is no way left to get rid of the cached copy, until the cached copy expires automatically (30 days ?). For wildcard, you propose sending a purge request for every possible image size. This would be highly inefficient however. You would replace one bounded set of requests (often no more than 10 or so) with 10000 of requests (for each possible size) and that for thousands of images that are purged every hour. Caching really is a rather special problem that breaks the rules of many of the expectations that people tend to have. -- Configure bugmail: https://bugzilla.wikimedia.org/userprefs.cgi?tab=email ------- You are receiving this mail because: ------- You are on the CC list for the bug. _______________________________________________ Wikibugs-l mailing list [email protected] https://lists.wikimedia.org/mailman/listinfo/wikibugs-l
