Kai Krueger schrieb: > On 22/07/28164 20:59, Dominik Bay wrote: >> Hi all, >> >> I'm coming up with a topic for discussion on how to save and >> serve OSM data for Slippy Maps, Mobile Devices and handling >> routing-requests. > > I am not entirely sure what you are trying to achieve with this topic > and who you are targeting with it (Osm sysadmin? potential donors? The > community and what they want from OSM, or are you planning on donating > Hardware your self?), but I will try and comment on some of the points > about the rendering.
Mainly OSM Admins/Developers on planned features, resolving bottlenecks and in the end donating/setting up additional infrastructure for it. >> ==== >> >> 2. Why do we need it? >> --------------------- >> Due to growing Software based on OpenStreetMap and OpenRouteService >> we need a more-realtimish behaviour of our data, to serve mobile >> Users with actual tiles and a fast route calculation. > > Not sure what your definition of "more-realtimish" is, but I would say > our rendering is already approaching "near realtime" At least the main > mapnik layer should currently only have a lag of about 5 to 10 minutes > behind the main OSM database. During load spikes it could be more, > although with the new render server put in place a week or two ago, we > haven't really seen any times when the rendering couldn't keep up. > Furthermore, with the new replication mechanism of diffs, that is > starting to be tried out, this lag may get reduced even further to about > a minute. There is a potential that it feels less realtimish to users > though due to client side caching. Tile expiry for proxy servers is set > to something between 3 and 6 hours currently, so if you have visited the > map before the edits, your browser may still cache the old tiles for > that duration. The ti...@home layer I think also aims to achieve > rendering turn-around times of 10s of minutes to couple of hours, so > isn't that much behind mapnik either. Ok, that's something I wasn't aware of. Thanks for pointing out :) >> We also need to get tiles *fast* to our users, this is why they are >> called *Slippy* Maps ;-) >> (They are fast at the moment, thanks for your work on mod_tile, I'm >> impressed!) > > Yes, the current server can quite happily sustain the full 100Mbs link > that we currently have available which was demonstrated again the other > day during the load spike caused by the TV program Quarks and Co. That's good, so the Backend is already being able to serve many Users ... > The response time of a single tile should be anywhere between 50ms if > the tile is currently cached and you have a good connection to where OSM > is hosted to about 3 seconds, if it tries to render the tile on the fly > but is too complex to do so and times out to return a slightly older > cached tile. Which is pretty fast as well. ... but still depends on a low latency to the User who is requesting tiles. Therefore I am aiming to atleast get that on the same level anywhere, which does not count in Latency generated by slow links, packetloss etc. We can't do anything about this problems. > So at the moment the problem with tile serving, if any, is a question of > hosting and the increasing bandwidth requirements OSM has. During > typical daytime tile serving uses about 50 - 60 Mbs sustained with night > time dropping to 10Mbs. (ti...@home and cycle map not included) Which is not much traffic yet but involves a single point of failure. If this box dies, no tiles are served. Do you have any ideas of traffic distribution to US/EU/ASPAC? Serving US out of EU wouldn't be that efficient (to keep the ~50msec as a standard), so it would be nice to start with some proxies in the US. >> 3. A short description of what can be done >> ------------------------------------------ >> We can make use of things like Anycast and Geo-aware Caching. >> This means a user connects to a Tile-Proxy which is near his >> ISP (routing-wise) and holds all tiles which are relevant for >> the users location (Europe for example) plus the Tiles which >> are requested often (big Cities). > > Yes, that could theoretically be done, and there have been two > successful tests in the past with using Wikimedia proxyies. So software > wise this could presumably be done. Software is not everything though > and for this to work, you also need the proxy caches and the hosting. So > again, the issue here as far as I can see it, is hosting. But I am sure, > if ISPs or datacenters are willing to donate free, reliable hosting with > 100Mbs - 1000Mbs network links, we could scale up our current tile > serving quite well. But for the moment, we are limited to the resource > we currently have. I'm working on it ;-) More is coming in the next (two) week(s) I think, so I can give you more details on specific things. >> To get a better understanding of the next lines, feel free to open this >> picture:<http://eimann.etherkiller.de/nmz/osm.png> >> -> Rendering >> ------------ >> The goal is to get nearly-realtime rendering of all map-types and the >> option to easily do customized rendering for supporting events, >> Wikpedia, etc. >> This also enables us to support rendering of 3D Layers with very low >> delay. > > As I said above, we basically already have near-realtime rendering of > the standard mapnik layer. Providing customizabile tiles of maps, I > don't think, should be the core focus of the OpenStreetMap project > itself. For that I think companies and projects like Cloudmade, > Geofabrik, or Tiledrawer.com are much better suited which have sprung up > around the OSM dataset. In my opinion OSM should provide, with respect > to rendering tiles, a sufficiently high quality map so that the general > public is attracted to OpenStreetMap which then hopefully lowers the > barrier of entry to start editing and improving the data. But that goes > into the political question of what OSM stands for and what it wants to > offer. I agree on that, I was just an Idea to present an additional usecase of the data. > But why exactly are you putting specs together? Are you planning on > hosting your own rendering infrastructure or donating hardware to OSM? Yep I'm currently collecting on things which already have been done, and what we can improve. To not just putting a text together I'm also working on getting the ressources in place to kick off with some stuff end of 2009. Thanks for your explanations. :) Best regards, Dominik _______________________________________________ dev mailing list [email protected] http://lists.openstreetmap.org/listinfo/dev
