[ubuntu-web] Ubuntu Wiki

Alan Bell alan.bell at theopenlearningcentre.com
Fri Nov 12 08:15:48 GMT 2010

On 11/11/10 22:52, John Baer wrote:
> What version of MoinMoin are we running?
> John
moin version 1.6.3

The issue with the wiki is that the Xapian search engine is turned off. 
That is the beginning and the end of all the performance issues, the 
timeouts that cause 500 errors and all the complaints about how much the 
wiki sucks and why we should switch to wikimedia. It is *the* issue with 
the wiki. Without Xapian turned on every search is a brute force full 
text search across the entire corpus of text that is wiki.ubuntu.com. 
OK, so you may thing, what is the big deal, searches take ages, so what? 
Well there are a lot of pages that include search results, 651 to be 
precise, here is a list of them: 
https://wiki.ubuntu.com/AlanBell/fullsearchpages (some are OK and are 
just displaying a search box, some do a search on open of the page)
if you see something that looks like:
then that page will take 30 seconds or so to open as it hammers the heck 
out of the server for 30 seconds reading through the entire wiki. 
<<FullSearch()>> by itself is ok, that just displays a search input box 
and <<FullSearchCached(searchterm)>> is OK as the search is cached (just 
doesn't update until someone deletes the cache for that page then it 
takes 30 seconds to reload)
OK, so these broken pages are slow, and also anti-social as they place a 
massive load on the server slowing it down generally for other people. 
In theory someone could go through these pages and change them to use 
cached queries, or we could just live with these being slow.
Now we come on to the *big* problem. Page subscriptions are not stored 
on the pages themselves, they are stored on the user profiles, you can 
go to your user profile and see the pages you are subscribed to, which 
can include wildcards picking up even new pages in a part of the wiki 
namespace. So when you save a page on the wiki it has to send a 
notification email to anyone who has subscribed to the page. Can you 
guess how it finds the people to send mails to? hint: it takes about 30 
Turning on Xapian is simple. Really simple. Here is how to do it 
http://moinmo.in/HelpOnXapian So why have we endured multiple years of 
pain and frustration? Well we are on sucky old 1.6.3, if you have a look 
at the release notes you will see that a number of Xapian related 
crashes have since been fixed http://moinmo.in/MoinMoinRelease1.8. The 
current release of moin is 1.9.3 and we have this in maverick. 1.9.2 in 
Lucid LTS would be fine too.

python-moinmoin (source: moin): Python clone of WikiWiki - library. In 
component main, is optional. Version 1.9.3-1ubuntu1 (maverick), package 
size 14659 kB, installed size 25140 kB
python-moinmoin (source: moin): Python clone of WikiWiki - library. In 
component main, is optional. Version 1.9.2-2ubuntu3.1 (lucid), package 
size 14469 kB, installed size 25612 kB

So why has nobody gone and upgraded our paleolithic moin instance? Well 
there is a little bit of non-standard tinkering that went on to 
implement Launchpad integration. I don't believe it is much, and I am 
fairly sure it would not be a big job to port that to a modern version, 
if indeed any change was required. Moin has not had any major 
architectural change that I can see and themes I have been developing on 
1.9.2 seem to run just fine on 1.6.3.

Having discussed this with the web team it was suggested that I should 
push for an upgrade to be discussed at the next UDS as nothing is likely 
to be done before then, so this is me, starting to push for it, right 
now. If you are a wiki user, particularly if you have been doing less 
stuff on the wiki because it is just such an unproductive place to work 
then do join in the conversation and lets get this thing fixed. The 
problem is not unknown, moin does not inherently suck, transitioning to 
mediawiki would be disruptive and much much more work than just 
upgrading to the supported and packaged version in Ubuntu and turning on 
the Xapian option.


Alan Bell
The Open Learning Centre

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