[OSM-dev] Daily Planet.osm
frederik at remote.org
Mon Apr 30 09:20:22 BST 2007
I am a fervent advocate of instant access for every imaginable
type of request. Give me all data for Australia, as it is NOW, not as
it was an hour, a day, or a week ago! Databases are for direct
access; anything else must surely be a compromise.
That said, I fully understand that we have to make many compromises
at the moment (but that should not cloud the vision!).
Nick Hill asked:
> Where is a daily dump useful, where a weekly dump is not?
Mostly for map rendering, which is one of our main "shopping windows"
to the outside world. Every mapnik layer renders off a planet dump. A
daily dump is therefore useful for the following six things:
* less than 24h old maps on Thursday
* less than 24h old maps on Friday
* less than 24h old maps on Saturday
* less than 24h old maps on Sunday
* less than 24h old maps on Monday
* less than 24h old maps on Tuesdays
The tiles at home rendering layer would also be affected. As most of you
know, even though we have the RSS feed and the ability to manually
request rendering of tiles, a lot of changes are missed. Most
Wednesdays I take the planet file and the full t at h tile statistics
file (issued daily), and compare last modified times for the area of
each tile, to find out which need re-rendering. At times, I have had
to re-request as much as 10,000 tiles to bump the t at h layer up to a
resonably current view - which led to a big workload for all parties
involved (database server, t at h tile server, and clients) on
Wednesdays and Thursdays, that would much better be evenly spaced.
> And is a daily dump
> likely to lead to an overall benefit to OSM?
If you count our image as viewed from the outside, yes, current maps
are important. If I describe the project to others, it is obvious
that the main fascination there is that "this is a map you can edit"
- and people expect the "edit" to bear visible fruit. It is bad
enough that such fruit needs half an hour to ripen with the
tiles at home layer, but telling people that the edit I just made will
show up on the main map "sometime after next Wednesday" really bursts
a lot of soap bubbles. If I could say "tomorrow", that would still
not be perfect, but make a difference. Every little helps ;-)
Frederik Ramm ## eMail frederik at remote.org ## N49°00.09' E008°23.33'
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