[OSM-talk] Contours server (was: Re: ski pistes)
steve at nexusuk.org
Mon Mar 17 17:43:51 GMT 2008
On Mon, 17 Mar 2008, Dave Stubbs wrote:
> There's also the amount of time it would take to render the tiles. It
> takes over 15 hours to render the contours used on the cycle map, and
> all things considered that covers a very small % of the planet surface
> at any kind of decent zoom level. It's a slow enough process that
> render on demand doesn't work so well either. So any such server would
> need a few TB of disk space or be a "come back in 24 hours" after
> request job, or both.
I've been quite successful with doing render on demand - tiles which
have never been rendered are pushed into a render queue and the HTTP
connection is left idling. If the tile is rendered within 30 seconds the
user gets it sent over the HTTP connection as soon as possible, otherwise
they get a 404 and the tile remains in the queue until it is rendered.
The render-server process is currently set to be able to render up to 4
tiles in parallel and also copes well with requests for tiles that are
already queued or being rendered.
That said, it is running on a pretty meaty server (an 8 core 1.86GHz Xeon
E5320), and it isn't very busy (serving 15k - 36k tiles per day over the
past 5 days). I suspect that storing the contours in PostGIS helps quite
a bit too.
My main performance issues revolve around importing the planet OSM file
(osm2pgsql uses up crazy amounts of RAM (or rather, swap, in my case) -
there is the "-s" option, but that is currently broken...). What I'm
really after is a way to import the daily diffs into the existing PostGIS
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