[Tilecache] Permissions and TileSize

Dane Springmeyer blake at hailmail.net
Thu Jan 8 17:13:40 EST 2009 

Matthew,

The first step in rendering smaller size tiles with TileCache Mapnik  
is to request 8-bit pngs.

Using TileCache trunk you can do that with:

extension = png256

Dane


On Dec 26, 2008, at 5:03 PM, Matthew Rushton wrote:

> Much better, that works as expected. Right now I'm looking into the  
> size of the png files that are produced which are ~3x bigger than  
> those I was producing previously. I was not using PIL before and I  
> suspect the images are not getting properly compressed. I'll keep  
> digging, if anyone knows of a quick fix let me know.
> -Matt
>
> --- On Fri, 12/26/08, Christopher Schmidt <crschmidt at metacarta.com>  
> wrote:
> From: Christopher Schmidt <crschmidt at metacarta.com>
> Subject: Re: [Tilecache] Permissions and TileSize
> To: "Matthew Rushton" <mrushton7 at yahoo.com>
> Cc: tilecache at openlayers.org
> Date: Friday, December 26, 2008, 1:34 PM
>
> On Fri, Dec 26, 2008 at 09:43:44AM -0800, Matthew Rushton wrote:
> > Thanks Chris
>  here's some more info:
> >
> > From my tilecache.cfg:
> >
> > [basic]
> > type=MapnikLayer
> > layers=basic
> > mapfile=/opt/tile_server/mapnik/osm.xml
> > size=64,64
> > tms_type=google
> > spherical_mercator=true
> > metaTile=true
> >
> > a request which I expect to produce the entire world but is part  
> of a 4x4
> grid:
> > myserver.com/tilecache.py/1.0.0/basic/0/0/0.png
>
> spherical_mercator=true implies maxResolution 156543.0339. You want a
> maxResolution of 4x that, if  you want the whole world in one 64 pixel
> tile: 626172.1356 . I don't know if the OSM.xml file actually has  
> rules
> to account for that, but adding maxresolution=626172.1356 to your  
> config
> will certainly get you closer.
>
>
>
> > Also I am using mod_python so perhaps the performance isn't as a big
> > deal if the xml isn't being read with every request that was a cache
> > miss. My basic concern
>  was how much faster could I make a custom
> > apache module if I were so inclined. Thanks again!
>
> Much faster, probably, but not in any important way. I've *never* seen
> anyone peg a CPU with serving cached tiles: I have seen TileCache  
> peg a
> 1gbps network connection, though.
>
> Again, the time to read the XML vs. time to render a tile is tiny. If
> you're concerned about speed, the most important thing to do is make
> sure your tiles are pre-cached, not worry about the TileCache time,
> which will be miniscule by comparison.
>
> -- Chris
>
> > -Matt
> >
> > --- On Fri, 12/26/08, Christopher Schmidt <crschmidt at metacarta.com>
> wrote:
> > From: Christopher Schmidt <crschmidt at metacarta.com>
> > Subject: Re: [Tilecache] Permissions and TileSize
> > To: tilecache at openlayers.org
> > Date: Friday, December 26, 2008, 11:47 AM
> >
> > On Fri, Dec 26, 2008 at 08:17:22AM -0800, Matthew
>  Rushton wrote:
> > > I finally figured out the issue, it ended up being a boundary file
> > > that had the wrong permissions, so all is good and appears to be
> > > working. One issue that remains is my tile size. I'm using 64x64
> and
> > > this makes zoom level zero not be the entire world.
> >
> > This isn't enough information to understand what you're hoping
> for.
> > Please share your TileCache config and a tile that you're looking  
> for.
>
> >
> > > The only other issue I was curious about was performance with osm
> > > data. I'm worried about the xml file being parsed too frequently.
> > > Does  anyone have experience with this? Is my concern valid?
> >
> > Since:
> >  * Pre-cached tiles never touch the XML file
> >  * Non-precached tiles will take much longer to render than to use
> >    a C-based XML parser to read the XML file
> >
> > My
>  guess is that your concern is a case of premature optimization.
> >
> > If you are using mod_python, the config file is read once per apache
> > child startup. If you are using CGI, it is read with every request  
> that
> > needs to generate tiles.
> >
> > -- Chris
> >
> > > -Matt
> > >
> > > --- On Thu, 12/25/08, Matthew Rushton <mrushton7 at yahoo.com>
> wrote:
> > > From: Matthew Rushton <mrushton7 at yahoo.com>
> > > Subject:
> > > To: tilecache at openlayers.org
> > > Date: Thursday, December 25, 2008, 10:09 PM
> > >
> > > I'm trying to set up TileCache and running into a few problems
> with
> > likely simple solutions. I'm using Mapnik to render the tiles to a
> disk
> > cache. I previously was using another tile server, so I know  
> mapnik is
> working
> > great. This is the error I'm getting below. I know it's a problem
> with
> >
>  loading the osm.xml file I just don't know why. I've changed
> > persmissions so it shouldn't be an issue. What sort of problem could
> this
> > be? What do people generally keep the permissions of this file and  
> others,
> > including tiles, at. Thanks in advance.
> > > -Matt
> > >
> > > An error occurred
> > >
> > > : failed opening file: Bad file descriptor
> > >   File "/var/www/tilecache-2.04/TileCache/Service.py", line
> 224,
> > in modPythonHandler
> > >     host )
> > >   File "/var/www/tilecache-2.04/TileCache/Service.py", line
> 208,
> > in dispatchRequest
> > >     return self.renderTile(tile,
> > >  params.has_key('FORCE'))
> > >   File "/var/www/tilecache-2.04/TileCache/Service.py", line
> 138,
> > in renderTile
> > >     data = layer.render(tile)
> > >   File "/var/www/tilecache-2.04/TileCache/Layer.py",
>  line
> 437,
> > in render
> > >     return self.renderTile(tile)
> > >   File
> "/var/www/tilecache-2.04/TileCache/Layers/Mapnik.py",
> > line 40, in renderTile
> > >     mapnik.load_map(m,self.mapfile)
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > > _______________________________________________
> > > Tilecache mailing list
> > > Tilecache at openlayers.org
> > > http://openlayers.org/mailman/listinfo/tilecache
> >
> >
> > --
> > Christopher Schmidt
> > MetaCarta
> > _______________________________________________
> > Tilecache mailing list
> > Tilecache at openlayers.org
> > http://openlayers.org/mailman/listinfo/tilecache
> >
> >
> >
> >
> -- 
> Christopher Schmidt
> MetaCarta
>
> _______________________________________________
> Tilecache mailing list
> Tilecache at openlayers.org
> http://openlayers.org/mailman/listinfo/tilecache

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