[Tilesathome] Towards a more efficient lowzoom

[Martijn van Oosterhout]

On 6/5/07, Frederik Ramm <frederik at remote.org> wrote:
> Can you not simply download the latest.txt.gz metadata file each day and
> run your script based on that? No database access required, and if you
> envisage a 1-day latency anyway...

Almost. There is currently no way to detect changes in the blank tiles
list. But that will come eventually I suppose.

> One big problem I see with your method is that, if you miss a change for
> any reason, you might upload lowzoom tiles that do not reflect the
> current situation, e.g.

<snip>

Yes, it's a corner case, and a fairly big one, especially if you're
dealing with data from latest.txt.gz. Ideally the timestamp in the
database after uploading the lowzoom tiles should reflect the
timestamp of the latest.txt.gz so that changes will be picked up the
next day, but I'm not sure if the server recognises the timestamp of
the files anyway.

Similarly tiles uploaded by normal clients should be timestamped with
the moment the data was downloaded from the server. I don't know if
that happens currently either.

These are both solvable, *if* the server can be told the timestamp to store.

> Otherwise, +1 for any kind of automated lowzooming. (Your optimisation
> would probably be irrelevant if we had a resonably fast machine. I used
> to be able to refresh *all* level-11 and smaller tiles in less than a
> day, back then when the server was responsive. And if it were done on
> the server's local network, it would be even faster. Sigh.)

I agree, but the machine isn't responsive, so I'm thinking of ways to
minimise the load...

Have a nice day,
-- 
Martijn van Oosterhout <kleptog at gmail.com> http://svana.org/kleptog/