[OSM-dev] JOSM patch to request T at H renders

Robert Hart bathterror at gmail.com
Fri Mar 23 08:25:29 GMT 2007


On 23/03/07, Frederik Ramm <frederik at remote.org> wrote:
>
> Hi,
>
> > I've been working on a patch for JOSM that will request tiles at home
> > updates whenever data is uploaded.
>
> I don't know if you have seen my "slippymap" plugin (in SVN). It
> currently displays a map tile grid and has the ability of loading and
> displaying slippymap tiles. I had the intention of expanding that to (a)
> be able to request and display tile metadata ("this tile last rendered
> at ...") and (b) to allow the manual issue of re-rendering requests.
>
> I still think that avenue would be worth pursuing; especially trying to
> support various (probably even configurable) slippymap layers instead of
> only t at h, but I also believe that manual requests make more sense than
> automated ones.
>
> In the worst case, your automated solution will lead to a tile being
> re-requested multiple times in short intervals, and given that some
> renderers are faster than others, it might actually happen that a
> generated tile is overwritten by an older version (JOSM user uploads
> change, slow renderer grabs request, JOSM user uploads other change,
> fast renderer grabs request, fast renderer uploads latest tile, slow
> renderer uploads older tile).



Bear in mind that requests are already automatically queued on upload via
the RSS feed. This approach just makes it more bullet proof, and avoids the
need for T at H polling the main server.

Problems with multiple renders can, and should be, fixed with the
T at Hserver. For example, it could pass an ID to the client with each
batch of
work, which the client will pass back on upload. Alternatively the client
could set the modification time on images to that of the OSM data, and then
the server will be able to only update images that are newer than those
existing.

I can add a "request tile updates" check box to the upload data confirmation
window, and of course I will add preference file entries for the t at h server.

Rob
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