[Tilecache] Missing Tiles

[Christopher Schmidt]

On Tue, Feb 17, 2009 at 10:25:00AM -0600, Terry Austin wrote:
> All,
> On a Windows Vista / Apache 2.2 / mod_python / TileCache 2.10 -> MapServer
> WMS / OpenLayers setup with no pre-seeding, I'm seeing missing tiles on
> virtually every significant load of tiles in a given view like when changing
> resolutions or when the view requires loading a lot of tiles because of a
> pan.  This only occurs when the metaTile option is on.  Turning off
> metaTiling makes all tiles appear (but has the visual limitations of not
> using metatiles).  I'm seeing this in my Apache logs with about the same
> frequency as the missing tiles:
> 
> unlock
> D:\Data\Gis\TN\tilecache\tn\version00001\all\07\000\000\060\000\000\013.png.lck
> failed: [Error 2] The system cannot find the file specified:
> 'D:\\Data\\Gis\\TN\\tilecache\\tn\\version00001\\all\\07\\000\\000\\060\\000\\000\\013.png.lck'
> 
> Not sure if that has anything to do with it.  Does this seem like a locking
> issue (only metatiles use locks?), or is it some wacky Vista TCP limitation
> thing?  I think that the tile is actually generated because reloading the
> page makes everything appear correctly.  Also, just using the URL of the
> missing tile in another browser tab works correctly, so I know the tile can
> be generated.

How long do your metaTiles take to render? if your metaTiles take > 30s,
then this is expected behavior; anything that waits longer than 30s by
default will get an error message (specifically,                 raise
Exception("You appear to have a stuck lock. You may wish to remove the
lock named:\n%s" % self.getLockName(tile))
).

You can configure this timeout by the 'timeout' parameter of the Disk
Cache section.

Regards,
-- 
Christopher Schmidt
MetaCarta