[OSM-dev] Rendering Strategy

[Stephan Knauss]

Mi Markus,

On 20.12.2010 11:33, marqqs at gmx.eu wrote:
>> Why not rendering them as soon as possible? mod_tile[1] will help you
>> with
>> this.
> Yes, interesting software. That would mean to render on the fly. I am
> not sure if my weak virtual server would cope with the task doing both
> at the same time, rendering tiles and serving tiles.
Try to mark tiles dirty when they are updated.

For mod_tile:
You should play a bit with the timeout parameters.
ModTileRequestTimeout

If you set a very short timeout the user will receive the old tile. In 
the background you will have tirex render the tiles. This can be done on 
a low priority.
Worst case: the tiles will not be rendered until load is low (maybe 
during the night) This would be the same as your original plan.
In the best case the load during daytime is low enough, so tiles are 
fresh earlier.
You can even start to render dirty tiles in the background in case a 
user requests them in the future.

> Thus, the rendering process could pick all the old
> tile image files at night and start their rerendering.
In case the load gets not low enough to finish rendering of the queue 
you have a problem.
Then also your original idea can not work. You could switch off tile 
expiry and expire based on the age of tiles. Or do the rendering on a 
different machine and upload tiles to the server.

Stephan