Wikitech-l May 2002

wikitech-l@lists.wikimedia.org

22 participants
89 discussions

response times
by Lars Aronsson 22 Aug '02

22 Aug '02

Today Friday, the front page of the English Wikipedia has been fast all day. Another page (I monitor http://www.wikipedia.com/wiki/Sweden) was slow for one period of 30 minutes (09:30-10:00 am GMT) and another period of two hours (11:40-13:50 GMT). Some other URLs on the international Wikipedias were also affected at the same time. This might be due to maintenance or work being done on the scripts. Subtract 7 hours from GMT to get the server's local time zone (PDT = GMT -0700). Apart from these two limited intervals, every URL that I monitor have been fast all day, including the recent changes pages. I'm very happy with this, and hope Brion and Jimmy (and who else?) will soon get the talk namespace links back without hurting performance. (But hey, never make big fixes five minutes before you leave for the weekend! Better just leave it as is if you have to go.) And now for some more relaxed Friday reading, actually related to performance problems. (The following analysis might be politically slanted. Don't take it too seriously.) The Swedish parliament elections are coming up in September, so the political parties are starting up their campaigns. The problem is there are no big issues to fight about. The four non-socialist parties have unusually boring candidates (Dukakis style), and everybody expects the current social-democratic government to win. The single issue that seems to be coming up is the national sick leave insurance, which is paid by tax money, and far over budget. This is linked to the fact that "burn-out" is now an accepted medical diagnosis for which you are allowed to take a long sick leave on the tax payers' expense. You would expect such welfare excesses to be on the social democrat agenda, and that non-socialists would urge for tax cuts and a balanced budget. However, the current s-d govt has been doing a great job balancing the budget, and they will now have to deal with cutting back this overgenerous sick leave compensation without hurting their voters' feelings. Tough job. The Christian-democratic party's candidate has already hurt a lot of feelings by claiming that "some" of those receiving compensation are "cheating the system". That might be true, but accusing "some" (who? me?) is obviously not the way to attract voters. This issue now has media attention and some interesting example cases are reported. Like this one: Attorneys in Swedish district courts have been right-sized in the past years, as part of balancing the budget. This means that as soon as one gets sick, the rest get too much to do, leading to stress and burn-out, which leads to more sick leaves. Think of the court cases as HTTP requests arriving to Wikipedia. There are some processes/attorneys there to handle the cases, but for some reason one process gets blocked and cannot work. This leaves more work for the remaining workers, but they are probably waiting for the first process to get finished and unlock the resources (database records?) that it is using. If processes are allowed to go to sleep waiting for each other, the work will pile up. It will never end. So, what is the solution? Throwing more attorneys at the problem? Maybe, but more likely the work processes should be redesigned and simplified. That allows the available attorneys to finish up a case and take on the next one. Some of their tasks are more important than others, but the performance or throughput of the system depends on cutting away or redesigning the most time-consuming tasks. The high degree of sick-leave is an indicator of system design flaws (albeit an one), and thus not altogether bad. In the same way, a high "load average" (as reported by the "uptime" or "top" commands) is one indicator that the Wikipedia system is flawed. The load average in a UNIX system is the number of processes that are ready to run, waiting for the CPU to become available. Unfortunately, most of them are just waiting to see if their wanted resource has become available. If this is not the case (e.g. database record still locked), they will go back to the end of the line, waiting again. Do you remember those bread shop waiting lines in Soviet Russia? Training new attorneys is in itself a time-consuming task, which should be avoided if possible. Instead of paying sick leave (for how long?) to the already trained attorneys, a "cure" for "burn-out" should be found that can bring them back to work, thus relieving the overload from their colleagues and saving tax payers' money at the same time. I have no idea how a "cure" for burn-out can be found, but I think it is a necessary political trick, and thus will happen. It will not hurt voters' feelings, and it is my guess that the people who can achieve this will work for the winners of the election. This might be the weakest analogy in history, but I think we should treat the Wikipedia processes with the same dignity and respect that the Swedish voters would expect. After all, they're supposed to work for us. The processes feel self-fulfillment when they can finish their job on time, and get distressed when they get locked up. Any uncalled for delay will only result in more work piling up. That is a flaw in the system design that has to be fixed, and we cannot go around claiming that "some" of the workers are trying to cheat the system. That will only lead to us losing their confidence. -- Lars Aronsson (lars(a)aronsson.se) Aronsson Datateknik Teknikringen 1e, SE-583 30 Linuxköping, Sweden tel +46-70-7891609 http://aronsson.se/ http://elektrosmog.nu/ http://susning.nu/

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links in the sidebar
by Jason Richey 04 Jun '02

04 Jun '02

I couldn't help but notice that the link in the sidebar that refers to today's date doesn't have the spaces escaped. So, instead of clicking through to "http://www.wikipedia.com/wiki/May+21", you go to "http://www.wikipedia.com/wiki/May 21,2002", which puts you at "http://www.wikipedia.com/wiki/May". Perhaps this was intentional... -- "Jason C. Richey" <jasonr(a)bomis.com>

3 2

Stream-oriented diff algorithms
by Axel Boldt 30 May '02

30 May '02

The difflib code which I took from phpwiki can be used for stream based diffs (in fact, we do that: we first use a line based diff to figure out the lines to present, and then we do a word based diff on those lines in order to mark the changed words red.) The code works as follows (see http://cvs.sourceforge.net/cgi-bin/viewcvs.cgi/wikipedia/phpwiki/fpw/diffli…): The main workhorse is the Diff class. You construct it with two arrays of strings that you want to compare. You then get a list $this->edits; this is a list of _DiffOp's which describe how to get from the first array of strings to the second array of strings with a minimal number of changes. With that, you can do whatever you want. Normally, you'd pass such an Diff object to a DiffFormater (which you should extend), which then looks at the edits list and produces some output. Currently, we cut the two article version into lines, pass those two arrays to Diff, then to TableDiffFormatter for presenting in a table. This TableDiffformatter, when printing out changed lines, calls a WordLevedDiff (which extends Diff) to color changed words in red. It might be nice to change TableDiffFormatter to produce side-by-side output, similar to what the sourceforge cvs viewer does. Axel

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Stream-oriented diff algorithms
by lcrocker＠nupedia.com 29 May '02

29 May '02

The next major issue to tackle with the new code is diffs. What I'd really like to find is a stream-oriented difference algorithm rather than a line-by-line one. I'm not familiar enough with the existing difflib to know if it could be used that way--perhaps its contributor could point me to some documentation on it?0

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Status of new codebase
by lcrocker＠nupedia.com 28 May '02

28 May '02

The new codebase running on http://www.piclab.com/newwiki/wiki.phtml is now ready for some real testing. I intend to keep this one "stable" as I add the remaining features--I have another experimental setup to use during development. It now has the basic features needed for view and editing articles, including redirects, article histories, recent changes, and all the user login functions. It has the full wikipedia database from 5/20. So I'd appreciate it if you could take a minute and test the existing features and tall me (1) if anything is broken, and (2) if the small changes I've made to aren't so small in you opinion. Don't bother telling me what's missing--I know most of it still is. 0

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google and umlauts
by Kurt Jansson 27 May '02

27 May '02

Google doesn't seem to like our umlauts in page titles. Try http://www.google.de/search?q=%C3%84nderungen+site%3Ade.wikipedia.com&hl =de&ie=UTF8&oe=UTF8 Google says "Ungültige Seite Letzte_Ãnderungen. " (which means "invalid page Recent_Changes"). Is it a problem on google's or on our side? Will it be solved with the new software? ---- The most important bug in the new software on test-de.wikipedia.com seems to be that the upload feature doesn't work. All others shouldn't be too hard to solve, but I'm no programmer :-) http://test-de.wikipedia.com/wiki/wikipedia:Beobachtete+Fehler Bye, Kurt

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What happened?
by Pierre Abbat 27 May '02

27 May '02

After half an hour of trying to access Procellariiformes to see what someone else added to it, I get this: Warning: Supplied argument is not a valid MySQL result resource in /home/wiki-newest/work-http/wikiUser.php on line 24 Warning: Supplied argument is not a valid MySQL result resource in /home/wiki-newest/work-http/wikiUser.php on line 32 Warning: Cannot add header information - headers already sent by (output started at /home/wiki-newest/work-http/wikiUser.php:24) in /home/wiki-newest/work-http/wiki.phtml on line 48 Warning: Cannot add header information - headers already sent by (output started at /home/wiki-newest/work-http/wikiUser.php:24) in /home/wiki-newest/work-http/wiki.phtml on line 50 Warning: Supplied argument is not a valid MySQL result resource in /home/wiki-newest/work-http/databaseFunctions.php on line 33 What happened? phma

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Database dumps
by lcrocker＠nupedia.com 26 May '02

26 May '02

I've spent more time than I care to admit loading, dumping, reloading, tranforming, testing, reloading...various wikipedia databases before settling on what I think the new format will be, but I made a discovery along the way that might be useful: The 05/20 database dump from wikipedia weighs in at close to 600 MB. It turns out that almost 200 MB of that is cache. In the new system, I'll write a function specifically for doing database dumps, but in the meantime I'd suggest that the next time you dump a tarball, clear the cache first (and don't forget to be careful of the timestamps when you do). 0

1 0

Linked list in "old" table
by Axel Boldt 24 May '02

24 May '02

>replacing the odd linked-list mechanism of >old page versions seems awkward. It could be replaced by simply >using revision numbers that would be common to both the "cur" and >"old" tables. Yes, I think the linked-list approach should go. Especially since the current codebase doesn't seem to use it. We saw a while ago that the [[Pim Fortuyn]] article has a broken linked list, probably produced by some database timeout, and yet the history page shows up fine, only the diffs are computed incorrectly. Every article should have a clean revision number, period. That way, there would be an unambiguous way to the n-th version of some article. The current mixture of oldid and version (look at the links on a history page) is a mess. Axel

2 1

php-wiki de
by Jason Richey 23 May '02

23 May '02

I have set up the test site at http://test-de.wikipedia.com/, I had to remove an insert from the newiki.sql because it was causing an error. Of course, I lost the exact text of the error somewhere, but it basically said that there was already an entry for Main_Page (the entry I removed looked like it may have been a discussion forum for the actual main page). However, it was a fairly large chunk. So, take a look. A diff to my modified newiki.sql is attached. -- "Jason C. Richey" <jasonr(a)bomis.com>

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Wikitech-l May 2002