Thread: [SailfishOS] [Announce] Native offline maps: OSM Scout Server
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rinigus is offline rinigus
2016-12-02 , 21:02
Posts: 1,414 | Thanked: 7,547 times | Joined on Aug 2016 @ Estonia
#43
Originally Posted by MartinK View Post
Maybe it could be also related to the old bundled urrlib3 (issue 146) ? I've updated it in the master branch, but it is not (yet!) in any released version. So users packages from OpenRepos & Jolla Store still run with the old urrlib3 and might be getting those errors.

That should hopefully not be an issue soon as I plan to release updated modRana packages today or tomorrow.
I already forgot about this bug, thank you for reminding about it! Yes, that's probably the reason behind the slower response. It got exposed when I switched from Qt-based HTTP server to microhttpd and is fixed in modRana's master branch. As far as I remember, the symptoms were very similar to what was described.

I am pretty confident that this is a reason for significant slow-down. We just have to wait 1-2 days to test it


Originally Posted by MartinK View Post
This is something I have been wondering about - is that really needed ? Couldn't OSM Scout Server check incoming tile requests against the bounding boxes/shapefiles of multiple data packs and return data for the first match ? Or, depending on cost, just run the query on one pack after another until there is a hit ?

Some heuristic can be applied for this to run all further queries after a hit on the same data pack until there is another miss. Users could also enable just some packs in the OSM Scout Server UI to reduce the number of lookups.
Something like this has been implemented by Lukas (@Karry) in his OSM Scout application, if I understand correctly. There are some significant hurdles to overcome for server if we want to do that.

Server renders the map in as many threads as you have CPUs. For that, it actually shares database access. If we want to render in parallel, we may end up having the same number of databases open. I think this may end up with too much RAM consumed by the server. So, we could start writing in some logic and lock/unlock threads depending on the accessed databases. Its all possible, but not trivial.

Alternative is to limit to a single thread and render one tile in a time. This may slow down it too much taking into account that the mobile devices may start lowering CPU frequency and switching off some cores when the load is about 1.

We can return to it a bit later. Maybe Lukas will implement it that way that it will be exposed via libosmscout anyway :-). Ideally, it would be solved on the library level and all applications using the library would benefit from it (server included).

We can try to formulate it as an issue and see when and how to resolve it.

Originally Posted by MartinK View Post
Also a related idea - client side pack specification. OSM Scout Server clients could specify data pack name for the lookup. They could get the available pack names either from OSM Scout Server via a special query or by other means (listing all folders the OSM Scout Server data folder or even by downloading data packs themselves and pointing OSM scout to them).
I was thinking at one point to add database and the stylesheet as a part of URL. Its possible - we just get the same problems as I was pointing out above.

I would suggest to get other issues solved first: better GUI, search, rendering, and routing come up into my mind on server side. Better routing support on the client part (voice commands?).

Originally Posted by MartinK View Post
Yeah, that's certainly not an easy problem to solve. I wonder how the commercial/proprietary navigation systems handle that ? Or do they just have larger areas (whole Europe, etc.) so they don't have to care about it ?
Routing between maps is possible. Many have solved it with what seems to be separate data packages: OSMAnd, MAPS.ME for example. From Valhalla's docs and few test runs, it seems that they also partition internally all the maps. So, its possible, just have to work on it. Corresponding issue is https://github.com/Framstag/libosmscout/issues/57

Originally Posted by MartinK View Post
Again - just a couple of ideas.
Keep them coming. Let's just hope that we can implement at least a fraction of them.
 

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