[OSM-talk] Mapnik rendering update

Robert (Jamie) Munro rjmunro at arjam.net
Sat Jan 26 13:55:50 GMT 2008


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Jon Burgess wrote:
| On Fri, 2008-01-25 at 22:35 +0000, Robert (Jamie) Munro wrote:
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|> Jon Burgess wrote:
|> | Once this first pass of the rendering is complete the mod_tile setup
|> | will have all the existing tiles fully rendered with the current planet
|> | dump and current map style. At that point I will switch over the
URLs on
|> | the server to make the new tiles live.
|> |
|> | The new system has already rendered 5M tiles in just under 24 hours.
|> | This covers all of zooms 0 - 12 and about halfway through zoom 13. At
|> | the current rate all the old 30M tiles will be rendered by about
|> | Wednesday next week.
|>
|> Now that you've done the slowest-to-render low zoom tiles, Why not just
|> bin the old DB and backlog and let the rest of the tiles render on
demand?
|
| I might do this once all the z16 or z17 tiles are done but with only
| z0-12 I fear I'll get lots of complaints about stuff suddenly
| disappearing from the map. The zoom levels 15 - 17 are by far the most
| numerous according to the histogram of tiles per zoom.

Are you able to say how many times each high zoom tile has been viewed?
I suspect that it most cases it will be 1 if they are rendered on
demand, and 0 if they are rendered from a backlog. There will be tiles
that have been viewed a lot - tiles in important cities or places with
lots of OSM activity, for example, but I suspect a lot of the 8 million
z17 tiles will never be looked again, at least not until their content
has been changed.

If we do get a backlog, then it needs to give priority to tiles that
have been viewed more than once, so that on a second viewing, a tile
will be rendered live, even if the system is a bit busy (but not a lot
busy, as it were).

If you do get complaints, you can always switch back.

Out of interest, do you have rough stats on how long tiles at each zoom
level take to render on average?

Robert (Jamie) Munro

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