[Openstreetmap] tile cacheing

[SteveC]

I was thinking of the opposite. We use squid for caching and there are
some fairly powerful tools for removing things from the cache, so a cron
job could wake up every ten minutes and look for whats changed in the
database and kill the tiles in the cache that contain those changes.

First I want to replace mapserver and speed up tile generation and only
render streets if the zoom level is sufficient...

* @ 20/10/05 10:10:34 AM simon at zymurgy.org wrote:
> Here's a thought:
> 
> if, as Steve said, the tiles are cached on the tile server for 48 hours, 
> then that means that even parts of the world that haven't changed still 
> end up with their cached tiles invalidated, and all the processing 
> required to re-generate them (and harassing the landsat server) happens 
> again.
> 
> It's clear within the database what parts of the planet have had new 
> line segments or nodes on them since they were generated, so rather than 
> just having a simple http cache expiry, when it does expire, it could go 
> off to the database and look to see if there's any alteration to the 
> bounding box covered by the tile since it was last generated. If so, it 
> would keep the same image cached for a futher 48 hours, or whatever. In 
> fact, if the database check is lightweight enough, the expiry time could 
> be a several minutes, rather than hours/days.
> 
> I'm not sure that the current API supports this (has anything in this 
> bounding box changed since time T) query, but it could be of huge benefit.
> 
> -- 
> Simon Hewison
> 
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have fun,

SteveC steve at asklater.com http://www.asklater.com/steve/