[Tilecache] multiple tile requests

[Matthew Rushton]

Christopher,
  Thanks for your response. I am seriously considering modifying TileCache as you suggested and will let you know. Multiple tcp connections is an option, but it doesn't seem super attractive to me on mobile. I'm currently using 64x64 tiles which makes for a sizeable number of concurrent connections. RouteMe looks like it does do this but it also has the standard 256x256 tiles I believe so performance is not as much of a factor. Does anyone else have any thoughts on this? Would other people use this potentially?
-Matt 


--- On Thu, 1/1/09, Christopher Schmidt <crschmidt at metacarta.com> wrote:

> From: Christopher Schmidt <crschmidt at metacarta.com>
> Subject: Re: [Tilecache] multiple tile requests
> To: "Matthew Rushton" <mrushton7 at yahoo.com>
> Cc: tilecache at openlayers.org
> Date: Thursday, January 1, 2009, 10:38 PM
> On Thu, Jan 01, 2009 at 05:52:07PM -0800, Matthew Rushton
> wrote:
> > Hi,
> >   I was curious if anyone has used/modified TileCache
> to be be able to
> >   request multiple tiles at once. 
> 
> I'm not sure what you mean.   
> 
> > The need to do this has arisen
> >   because of the extremely high latency on mobile
> phones (for example
> >   the iPhone maps app requests multiple tiles at once
> using a
> >   proprietary request format). Http pipelining is
> possible but it
> >   requires too much work on the client side to get
> right, and on some
> >   platforms simply won't work. 
> 
> Web browsers simply request multiple URLs at the same time;
> I don't see
> a problem with implementing that for other Mobile
> applications as well.
> As I understand it, Route-Me works against standard HTTP
> tilesets; I
> would assume it uses multiple concurrent HTTP threads for
> this. 
> 
> > Any thoughts on this? I was planning on
> >   writing my own apache module to do this but figured
> I would ask. I
> >   think an API involving multiple tiles makes sense,
> especially in the
> >   mobile/high latency world. Thanks!
> 
> I guess you want some kind of url from which you can
> request a set of
> multiple tiles to be returned to you? TileCache's
> extensibility doesn't
> quite extend to that level, but it wouldn't be hard to
> add.
> Specifically, you would use:
>  
>  * A new Service subclass: This would parse the URL,
> pulling out the
>    parameters that tell it which tiles to load.
> 
>    For the sake of the next Chunk, i've assumed this is
> called
>    MultiTile, and that any request for multiple tiles also
> has a
>    'multitile=yes' key/value param in the request.
> 
>  * A change around line 213 of Service.py, to add a second
> conditioal
>    to the 'list of tiles is an array' case:
> 
>     if req_method=="DELETE": xxx
>     elif params.has_key("multitile"):
>         from TileCache.Services.MultiTile import MultiTile
>         return ('application/octet-stream',
>                 MultiTile(self).serialize(tile)
> 
>     else:
>         # PIL case 
> 
> I would gladly accept this change in trunk given sufficient
> documentation of what multitile's 'request
> parameters' are. (It would
> probably make sense to use sets of TMS-Style z/x/y tile
> identifiers in a
> comma seperated list or something similar, possibly encoded
> in some way
> to let you shove more of them into a string.)
> 
> Regards,
> -- 
> Christopher Schmidt
> MetaCarta