>> I started working on a streaming XML output plugin for Osmosis. I was >> intending to take advantage of PuSH/PubSubHub messaging and maybe even XMPP >> (so that you get a 1-min delayed IM when someone changes something in your >> bbox). >> Anyway, TRAPI could use this same plugin to apply updates to their >> database. > > I've also spent a fair bit of time thinking about this type of thing. When > I first started work on the replication diffs I had in mind a server-side > daemon (using Osmosis internally) that would push changes to all connected > clients. It would allow a client to connect, specify which replication > number it was up to, receive all updates in a single stream, then continue > to receive live changes as they occurred.
These are things we talked about at the recent FOSSGIS conference. I planned to do a more detailed write-up but I don't know when I'll get to that so this is not finished. We too agreed that some kind of streaming/subscription to changesets would be a good idea. Our focus though was on the german dev servers so that not everyone would need to write an .osc parser and download the changeset files etc. > Several issues preventing this are: > 1. Writing it. I don't have much time to do it therefore I went with the > simplest approach that would work at the time. I'm spending some time on something like this as part of the OSMdoc rewrite. > 2. Cacheability. A push approach is non-cacheable and therefore would > increase the amount of bandwidth required. I suspect diff updates are small > compared with planet downloads though so perhaps this is a non-issue. I'd just don't care about that. We have enough resources. So I agree that this is a non-issue. > But I would really like to see it happen :-) I currently use AMQP (RabbitMQ) for message processing and it works very well. It is very flexible and it'd be easy to extend it with a PubSubHubBub or XMPP output. Mitja (of OpenStreetBugs) proposed just yesterday a filter that filters changes by the tags/changes involved so it would be very easy to subscribe to only the events you are interested in. This can be implemented in just a few lines of code. While we only thought about doing this on the german dev servers I've since gotten multiple requests/questions and suggestions that this should be integrated into the main OSM site. All that'd be needed would be a call in the Ruby API that sends a message (asynchronously, very fast) once a change has been made. This would make the generation of the diff files a lot easier and everything more flexible. I haven't yet asked anyone if this would be a possible. I know that this isn't the right topic (although the TRAPI could also use this system) but I wanted to take the opportunity to inform about our ideas. Cheers, Lars _______________________________________________ dev mailing list dev@openstreetmap.org http://lists.openstreetmap.org/listinfo/dev
