On Sun, Jan 20, 2008 at 10:17:21AM +0000, Tom Evans wrote: > Christopher Schmidt wrote: > > I'm working on creating interfaces that display OSM data as you > > drag > the map around. The interface requests data from OSM > > "on the fly" -- so every time the map stops moving, the old features > > are removed, and a new request is sent out. > > I had thought about something similar, but I must admit I hadn't even > considered sending the requests to the main database API. Data a > few days to a week old is adequate, so surely OSMXAPI or even a > server with pre-tiled static .osm files (if the volume really picks up) > would be better. > > Scaling read-only requests with multiple servers is easy, but read/write > much harder. Better to avoid hitting the core database unless you're > using an editor and actually need to check the up-to-date data.
Let me state some of the use cases I'm currently working against: * The Coastline viewer displayed a small section of disconnected coastline after last night's update. These are disconnected nodes that I'm having problems finding in JOSM. I want to display the section of coastline, select them in OpenLayers, and delete them. Potlatch won't work, because I can't see the coastline errors in Potlatch, and the section of map I'm working in is simply a total mess coastline wise, and I can't find the section that coastline editor is complaining about. * I'm going on vaccation in a couple weeks, so I've been tracing out my destination against Yahoo!'s imagery. Then, when I'm there, I want to use my OpenLayers editor (displaying tiles from my locally loaded planet) to edit the streets I haven't gotten yet. I can download data from the local db or from osmxapi -- but as soon as I want to edit a name of a road, I have to switch to the real API, because otherwise I might be editing against old data. * I'm editing and want to understand the tagging scheme that someone used on a particular set of data, so I can mimic it because it seems like what I'm looking for. I want to download the tags, click them to view them, and then use them i my other editor. This case is obviously served by the osmxapi without any problems. > Having said that, I agree it does pause a bit sometimes. But scaling > the read-only access and keeping the read/write access stable and > bug-free seems more sensible to me. Sure. Maybe the answer is "Sorry, waiting 5s for a request to start is the penalty you pay for needing read-write access." If so, that's fine. But if the reason that that is is because we don't have hardware -- that is, it scales trivially, as compared to the database being slow, which clearly does not scale trivially -- then it's good to at least know that's the reason. Regards, -- Christopher Schmidt MetaCarta _______________________________________________ dev mailing list [email protected] http://lists.openstreetmap.org/cgi-bin/mailman/listinfo/dev
