[OSM-dev] Daily Planet.osm

Frederik Ramm 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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