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

--- Comment #75 from Rob Lanphier <[email protected]> ---
Hi everyone.  Our apologies for the problems with caching.  We're monitoring
the situation, and will continue to monitor it.  As of right now, things
*should* be better, but there's still work that Ops needs to do to know that
for sure.

This bug, unfortunately, isn't a useful description of anything anymore, and I
can't in good conscience assign this to a developer or an ops engineer.  It has
become a place that people to vent about caching issues generally, and is more
heat than light.

There are at least three different issues that I can see:
1.  Squid/varnish cache contains images that aren't in Swift, and don't purge
because only images in Swift get purged.  This is the problem that Aaron
described in comments 8 and comment 9 of this bug.  We plan to fix this problem
after we fully migrate to Varnish, but it's a complicated fix, and won't happen
right away.  The workaround for this problem is in comment 18.  My response is
unchanged from comment 34.
2.  Multicast purge requests don't make it to all of the Varnish & Squid
caches.  This is most likely the problem that people are actually complaining
about the most in the past week.  This is generally an Ops issue, and in fact,
Leslie Carr is working on the problem, with help from others.  The issue is
that some of our routing/switch equipment doesn't reliably route the purge
requests to all of the places they need to be.  They have periodic fixes for
the problem, but we don't know yet if they have things configured such that the
problem will remain fixed.
3.  Cache purging issues are not monitored sufficiently.  This is bug 43449,
and is another issue that needs to be addressed by the Ops team.

I'm going to leave this issue open for now, but at this point, but once the
other issues get filed, I plan to close this issue and use the other bug
reports to track this.

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