[OSM-talk] Node download limits / Database priority

[Dirk-Lüder Kreie]

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Nic Roets schrieb:
> I recently tried to download a large part of the city I'm working on
> so that I could fix the "motorway" running through it, but I was
> forced to do it in pieces due to the limit on the number of nodes per
> download.
> 
> But anyone (including anonymous users) are able to submit a request to
> re-rendering of the entire city on
> http://dev.openstreetmap.org/~ojw/Browse/?x=2369&y=2351&z=12
> And if I understand correctly many large cities are frequently
> rerendered for various tilesets, taking up significant database
> resources.

This is not so. At least the tiles at home project has a "holdoff" time
that prevents automatic re-renders of tiles that have recently been
rendered.
It is, however, true that anyone could re-request a city tile as often
as they like, resulting in "many" requests to the db, *if* and *only* if
the request is always picked away by a renderer before the new request
is put in. Furthermore such requests are quite small, less than 1/10th
the area allowed by the api, so I suppose that doesn't put too much
strain on the api, and should that already small are contain too many
nodes it switches to areas less than 1/100th in size of the limit.

> Now I'd rather that my city be rendered only once I'm done editing
> than waisting my editing time on splitting downloads.

I agree that the rendering should take place *after* the bulk of the
editing has taken place, not at the first change.
However if you edit with JOSM and only save between steps and upload at
the end of the editing session, the rss, and hence the rendering
projects will not see your changes, until you actually upload, and
therefore only then start re-rendering.

The actual relative loads (renderers, editing software) should be
possible to discern from the web server access logs (user agent).

I presume that the tiles at home project has less a database impact as you
seem to assume, because the requested areas are quite limited in size
and the rendering takes relatively long, so the clients don't request
data that often (again, only the server logs can really show if this is
 indeed the case).

I have confidence that if there was a noticeable negative impact by the
rendering, and especially the excessive re-rendering of the same areas
over and over, measures would be taken to counter that.
if one wanted to DOS the api that could be much easier attained than by
frequently re-requesting the tiles to be rendered.

Dirk-Lüder "Deelkar" Kreie

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