[OpenStreetMap] #4501: Include API usage policy technical limitations into Capabilities

[Frederik Ramm]

Hi,

On 07/31/12 20:11, Kai Krueger wrote:
> On the other hand some of the more complex queries, like relation/full,
> the bottleneck is likely the rails processing. In that case, as long as
> there are still some spare CPU cycles left on the frontend/backend
> servers, again adding multiple threads might be a benefit. However, the
> backend servers will then run out of steam much sooner.

I think the situation is this:

1. People use relations as easy download handles all the time

2. This increases demand for /relation/full

3. The API has a habit of sending you "internal server error" for every 
second /relation/full that you try, likely because of some Postgres 
buffer limitations

4. Therefore people resort to downloading the relation without members 
and then hitting "download incomplete members" in JOSM

5. This results in JOSM fetching lots of "packages" of nodes/ways using 
the /node?nodes=id,id,id and /way?ways=id,id,id calls

Of course this is more wasteful than a working /relation/full call, and 
if /relation/full becomes more stable by moving it to cgimap, then the 
whole problem would probably be gone anyway.

People would then feel encouraged to use relations as easy download 
handles even more, and we'll see useful relations like "park benches in 
Bordeaux" and "picnic areas in Paris" more often. Yay!

Bye
Frederik


-- 
Frederik Ramm  ##  eMail frederik at remote.org  ##  N49°00'09" E008°23'33"