[OSM-talk] mapnik tile rendering - again

[David Earl]

> -----Original Message-----
> From: Martijn van Oosterhout [mailto:kleptog at gmail.com]
> Sent: 01 April 2007 22:32
> To: David Earl
> Cc: OSM
> Subject: Re: [OSM-talk] mapnik tile rendering - again
>
>
> On 4/1/07, David Earl <david at frankieandshadow.com> wrote:
> > I'm still puzzled by what causes Mapnik tiles to be rerendered.
> And I think
> > there is a rendering bug with highway=secondary at zoom level 11...
>
> http://wiki.openstreetmap.org/index.php/Slippy_Map#Mapnik_tile_rendering


What's described there is not what I'm seeing though. I *have* looked at
these areas many times at different zooms to see if they are rendered yet,
and they don't get re-rendered.

For example, a 'more osm coming soon' tile in the area I'm looking at:
  http://tile.openstreetmap.org/mapnik/15/16389/10784.png/status
  tile created at 2007-03-04 12:44:14
  tile is awaiting re-render: 1

So that's been in the queue since March 4th, nearly a month ago, without
being rendered.

And a rendered but out-of-date tile:
  http://tile.openstreetmap.org/mapnik/14/8193/5393.png/status
  tile created at 2007-03-27 13:45:50
  tile is awaiting re-render: 0
and its up-to-date neighbour
  http://tile.openstreetmap.org/mapnik/14/8192/5393.png/status
  tile created at 2007-03-31 17:49:36
  tile is awaiting re-render: 0

so even though I looked at both those tiles simultaneously, one got rendered
yesterday, and the other isn't even marked for rendering. While the newest
data for the former was uploaded on Wed 21 March, probably missing the
planet dump that day, and is therefore less than a week old but was rendered
with out of date data at that time, I don't understand why it differs from
its neighbour, which would have gone into the same planet file and have been
looked at on the same times as its neighbour.

Even if it is working as advertised, which I'm no convinced about
(especially in respect of the first example above), I have to remember to go
and look at an area a week after I've done the upload for it, and can't then
see the results until some time after that. If I leave it too long, the wiki
says they'll get deleted again.

Surely this isn't the best way. Is space very tight for storing tiles? Can't
I look at an area so it can get marked as dirty for the next planet dump?
And there doesn't seem to be any way I can reliably refer someone to a
particular area of map, because not all the tiles at different zooms will be
available even if I have looked at them myself. Basically the visitor who is
interested in the tiles doesn't get to seem them, but triggers a process of
re-rendering, which is too late as the visitor has lost interest. Should
their interest be revived some time later, chances are the tile will
probably have gone away again. I don't see the logic behind this at all: it
almost guarantees the person who wants to look at won't see what they want
to see.

If osmarender can store all its tiles, why can't mapnik? And if it could,
the queuing mechanism could be 'queue this tile for rendering when the next
planet dump arrives', as the casual visitor isn't going to wait around to
see if the tile is re-rendered (they won't know it might be, and then there
is the caching problem they also won't know about).

But even so, I don't think it is working as intended in the first place.

David