[Tilecache] Two tilecache instances not behaving identically.

Gissur Þórhallsson gissur at loftmyndir.is
Fri Mar 11 05:23:59 EST 2011


I've got a peculiar problem.

I have two tilecache services running on two separate machines. Let's call
them LIVE and SEED.

LIVE is in an active production environment delivering tiles to our clients
and works without a hitch.
SEED is an machine I have in-house on which I generate caches for LIVE.

LIVE is running:

   - Ubuntu Server 8.04. LTS
   - Apache 2.2
   - Python 2.5.2
   - Tilecache 2.11 running under mod_wsgi

SEED is running:

   - Ubuntu Server 10.10
   - Apache 2.2
   - Python 2.6.6
   - Tilecache 2.11 running under mod_wsgi

I've been accessing TileCache from OpenLayers using TMS requests for a while
and it seems to work fine - but if I try WMS requests I run into a problem.

Here is a an overview of what I'm facing, the following are snips from the
same OpenLayers client:
Live WMS <http://i.imgur.com/K58Qu.jpg> - ok
Seed TMS <http://i.imgur.com/nbnMA.png> - ok
Seed WMS <http://i.imgur.com/z3QdR.png> - not ok

Here are the configs for these layers. <http://pastebin.com/KN74QT2Y>

If I inspect one of those missing Seed WMS tiles at the following URL (split
up for readability):

I get the following:
An error occurred: Current x value 296528.805983 is too far from tile corner
x 143000.000000

These same coordinates work fine against LIVE - and if I take the  x value
and round it up I get
An error occurred: Current y value 408528.805983 is too far from tile corner
y 255000.000000

If I round the y value also ending up with:

I suddenly get the correct image.

So what that tells me, unless I'm missing something (which I guess I must
be), is that LIVE and SEED are not handling the coordinates the same way on
SOME tiles.
Which makes no sense what-so-ever.

Anybody have any ideas?

Gissur Þórhallsson

Loftmyndir ehf.
Laugavegur 13
IS 101 Reykjavík - Iceland
sími (tel): (+354) 540 2500
tölvupóstur (email): gissur at loftmyndir.is
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