[Tilesathome] lowzoom rendering takes forever?

Brent Easton b.easton at exemail.com.au
Sat Nov 24 01:18:57 GMT 2007



*********** REPLY SEPARATOR  ***********

On 23/11/2007 at 7:50 PM Christopher Schmidt  wrote:

>On Fri, Nov 23, 2007 at 11:21:08PM +0100, Thomas Stets wrote:
>>  [#33   0% jobinit] Doing tileset 146,99 (zoom 8) (area around
>> 37.158240,26.015625)
>>  [#33   0% lowzoom] Rendering...
>> 
>> It seems that the client is trying to do a lowzoom rendering, but its
>> been sitting at 0% for several hours now.
>> It still takes up one CPU (of my dual G5 Mac).
>
>Okay, this seems to be a serious problem. Since the enabling of lowzoom
>requests being handed out to clients, we've seen a significant downturn
>in the number of bytes being uploaded to the server, and a lot more
>tiles end up not completing in the 1.5 hours, and re-requested.
>
>I can't comment on exactly why this is, but I can comment that I'm
>seeing xmlstarlet taking minutes -- up to 10 -- to transform a single
>lvl 8 dataset. Tileset 126,83 (zoom 8) is currently on its 15th minute
>of renering, and it's only on 'Transforming zoom level 9'. (Now 22
>minutes in, and transforming level 10.) 
>
>I don't know anything about the client, but *something* isn't right
>here, and it might make sense to figure out what. 

I believe there is nothing wrong, that's just the way the new lowzoom works. 
The amount of data downloaded in a z8 tile can be huge for areas around well mapped cities. 

In the case of 126,83 you are looking at a 20Mb osm file which is equivalent in complexity to a moderately complex  AND Netherlands tiles.

The same problem of unrenderable Z16 and Z17 tiles applies to lowzoom tiles as well. The xslt conversion will probably complete eventually, but you will have a heck of a time rendering this tile with Inkscape.

The 1.5 hours timeout is probably a bit short.

Regards,
Brent.




____________________________________________________________
Brent Easton                       
Analyst/Programmer                               
University of Western Sydney                                   
Email: b.easton at uws.edu.au





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