Two players with the same ladder rank. Bug?


#1

The player just below me on the 19x19 ladder just challenged me this morning. Strangely enough, we appear to have the same rank #357 on both ladder screen and game information. Looks like a bug.
Not sure it’s linked, but since a few days, the ladder pages are very slow to upload (like 10s sometimes). Something broken in the ladder data base access?

I found at least another example at #216


Bug : ladder ranking duplicates
#2

Looking at the other ladders, it seems that the bug affects also the 13x13 and 9x9 ladders, since the number of players displayed on the main ladders page is out of sync with the rank of the last player:
13x13 : 408 players, rank of the last one 404
9x9 : 554 players, rank of the last one 545
As I just checked it, but there again, the loading of pages is very slow, and you’re never sure you have actually the last page of results even when it says so. The arrows “next page” changes the number of the page, but the content is lagging behind.


#3

It seems like the same lagginess that is affecting players game history, maybe related?


#4

Pinging @anoek because as @verlane said it sounds related to the game history display lag. Could be some kind of database fetch issue? Maybe check for integer overflow (amateur throwing out random suggestions that have already probably been tried)


#5

Pinging @anoek again, although he has certainly other, more important fish to fry.
@BHydden I don’t think it’s a data base issue. Since deployment on new servers yesterday, the access to ladder pages is far better, but the ranking bug is still there. I suspect it’s linked to the way the computing of new ranks after the victory in a challenge works. One thing is sure, it is that the way it works, once such an error (two identical ranks) is introduced, it is not corrected when new ranks are computed. Since my first post, I have winned a challenge and jumped higher in the ladder. The player skala above me took my rank, and as of today skala and carokarm are both #354. Which means when new ranks are computed, there is no verification of possible duplicates. So, two things might/should be done IMHO.

  1. Correct the current glitches by running a specific script checking for duplicates and pushing the ranks downward accordingly.
  2. The above is just a patch, and does not explain the origin of those glitches, which seem quite random. The origin has to be searched in the way the data base is updated after a winned challenge, is there an in-memory computing followed by a batch update, or is the data base directly updated, one player at a time? In any case, my hunch is that duplicates were caused by conflicting simultaneous updates.

I just ported this conversation under “support” category, where it belongs.


Please follow-up there. Thanks.