[OSM-Devserver] mod_tile/Tirex sometimes rendering checkered tiles

[Jochen Topf]

The black/yellow tiles are error tiles created by the backend if rendering
fails for some reason. In this case the WMS backend. I guess its because
the WMS request timeouted in the HTTP library. There is no timeout code
in Tirex at that point, so I guess it must be the library.

Jochen

On Thu, Jul 08, 2010 at 10:33:41AM +0200, Kay Drangmeister wrote:
> Date: Thu, 08 Jul 2010 10:33:41 +0200
> From: Kay Drangmeister <kay at drangmeister.net>
> To: "devserver at lists.openstreetmap.de" <devserver at lists.openstreetmap.de>
> Subject: [OSM-Devserver] mod_tile/Tirex sometimes rendering checkered
>  tiles
> 
> Hi.
> 
> I have a working setup with mod_tile + tirex/wms-backend + my_own_slow_wms_renderer
> 
> Sometimes, however, there are black/yellow checkered tiles like this one:
> http://drangmeister.net/tmp/44568.png
> 
> The according metatile looks like this:
> -rw-r--r--  1 tirex tirex    9108 2010-07-07 23:21 8.meta
> 
> i.e. is very short. About 70% of the metatiles are like this. This is although
> my renderer produced a valid image (seen in the rendering temp dir). So I presume
> this may be due to a timeout somewhere. I already set the following timeouts:
> 
> /etc/tirex/tirex.conf:
> 
> #  If the rendering of a metatile takes more than this many minutes the master
> #  gives up on it and removes the job from the list of currently rendering tiles.
> master_rendering_timeout=60
> (one hour)
> backend_manager_alive_timeout=57
> 
> /etc/tirex/renderer/wms/myrenderer.conf
> 
> - there is no timeout here. Correct?
> 
> /etc/apache2/conf.d/mod_tile.conf
> 
> # Timeout before giving up for a tile to be rendered
>     ModTileRequestTimeout 300 [<- pretty sure this means minutes, please confirm]
> # Timeout before giving up for a tile to be rendered that is otherwise missing
>     ModTileMissingRequestTimeout 100
> # If tile is out of date, don't re-render it if past this load threshold (users gets old tile)
>     ModTileMaxLoadOld 2
> # If tile is missing, don't render it if past this load threshold (user gets 404 error)
>     ModTileMaxLoadMissing 5
> 
> No other timeout that I can think of.
> My metatiles take about 3 to 5 minutes to generate.
> 
> Question: what part of my chain renders that checkered metatiles and why?
> 
> Thanks,
> Kay
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-- 
Jochen Topf  jochen at remote.org  http://www.remote.org/jochen/  +49-721-388298