80n schrieb: > On Tue, Feb 10, 2009 at 8:07 AM, Florian Lohoff <[email protected] > <mailto:[email protected]>> wrote: > > On Tue, Feb 10, 2009 at 07:47:12AM +0000, 80n wrote: > > How well will mapnik scale under load? > > > > As I understand it, most mapnik tiles are generated on-the-fly. > This is > > fine when you have a big server and only a few users. But when > you have a > > very large number of users (think Google maps) then would the mapnik > > approach cope with the load? > > > > It seems to me that t...@h is likely to be more scaleable when there > are large > > numbers of users. The t...@h machine will be mainly concerned with > serving > > images to the user rather than rendering and then serving. > > My guess is that mapnik can scale very good with little code added. > With the CPU power beeing the limit you can either limit the maximum > number of requests or when appropriate cacheing is applied limit the > currentness of the map. > > Pseudo code like this: > > if (!datachanged() && cachedtileavail) { > send(cached-older-tile) > } else { > if (length(renderqueue)*timetorender > 500ms) { > queuererenderrequest(prio 2) > if (cachedtileavail) > send(cached-older-tile) > else > send(More OSM Coming) > return > } > rendertile(prio 1) > updatecachewithnewtile > send(new-tile) > } > > Then one could use a squid to proxy to multiple mapnik backends based > on URL (e.g. tile xy number - read: geographic region) so one could > use a couple smaller machines which do not need to keep the full > database which makes the working set smaller and thus the database > faster. Once you are at google scale you have a machine per Z12 ;) > > Annother approach would be to seperate database, render engine and web > frontend. Rendering is typically CPU intensive and the database is > memory and io bandwidth intensive - So the renderer would have just a > "normal" amount of memory like 1-2 GB but tons of cores. The Database > would have tons of memory and tons of spindles but not necessarily a lot > of CPU. > > The only problem with mapnik would be a tons of user panning around > on previously unrendered territory which obviously cant happen to t...@h. > > > Well, yes, that is the scenario that I'm describing. What percentage of > the planet's tiles have actually been pre-rendered on the mapnik tile > server? >
I thought mapnik only renders the hourly diffs, not the tiles being requested? _______________________________________________ Tilesathome mailing list [email protected] http://lists.openstreetmap.org/listinfo/tilesathome
