Ori, thanks for following up.

I think I saw somewhere that there is a list of postmortems for tech ops disruptions that includes reports like this one. Do you know where the list is? I tried a web search and couldn't find a copy of this report outside of this email list.

I personally find this report interesting and concise, and I am interested in understanding more about the tech ops infrastructure. Reports like this one are useful in building that understanding. If there's an overview of tech ops somewhere I'd be interested in reading that too. The information on English Wikipedia about WMF's server configuration appears to be outdated.

Thanks,

Pine

Date: Thu, 29 May 2014 22:38:10 -0700 From: Ori Livneh ori@wikimedia.org To: Wikimedia developers wikitech-l@lists.wikimedia.org Subject: Re: [Wikitech-l] 404 errors Message-ID: CAHXK4ByYa8ae0EVGAUFWSCrjZtAQh+sjTW6ccJ14mB8o-teSoQ@mail.gmail.com Content-Type: text/plain; charset=UTF-8

On Thu, May 29, 2014 at 1:34 PM, ENWP Pine deyntestiss@hotmail.com wrote:

...

Hi, I'm getting some 404 errors consistently when trying to load some English Wikipedia articles. Other pages load ok. Did something break?

TL;DR: A package update went badly.

Nitty-gritty postmortem:

At 20:25 (all times UTC), change Ie5a860eb9[0] ("Remove wikimedia-task-appserver from app servers") was merged. There were two things wrong with it:

1. The appserver package was configured to delete the mwdeploy and apache

users upon removal. The apache user was not deleted because it was logged in, but the mwdeploy user was. The mwdeploy account was declared in Puppet, but there was a gap between the removal of the package and the next Puppet run during which the account would not be present.

2. The package included the symlinks /etc/apache2/wmf and

/usr/local/apache/common, which were not Puppetized. These symlinks were unlinked when the package was removed.

Apache was configured to load configuration files from /etc/apache2/wmf, and these include the files that declare the DocumentRoot and Directory directives for our sites. As a result, users were served with 404s. At 20:40 Faidon Liambotis re-installed wikimedia-task-appserver on all Apaches. Since 404s are cached in Varnish, it took another five minutes for the rate of 4xx responses to return to normal (20:45).[1]