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jolla map tiles are not cached (high mobile data usage)

asked 2015-04-08 09:20:10 +0300

c.la gravatar image

updated 2015-04-08 09:25:03 +0300

Hi, over several days I kept Jolla maps app open to cahe the tiles of an area where I commute often, so I can know where I am without eating much data. I did so sacrificing one month of 3G data allowance to download tiles.

I have downloaded for sure the tiles of a 200km trip on three different zoom levels. Data usage about 1,2 -1,5 GB.

Yesterday I opened the maps app and I saw the tiles showing up slowly, first the grey squares and then the map squares. Afeter few minutes I found out it was downloading the same tiles (max zoom level) again, eating up my mobile data (about 50MB or so).

Today I just turned off all internet connections and in fact the map is all grey at the lowest zoom levels.

I am surprised by this, I have plenty of space free on jolla (about 3,5 GB used) and no sdcard. How can I be sure to cache the here maops tiles once for all? Is that a bug?

Before returning the phone for repairs I never had this issue. The tiles were cached and retrieved from cache when I was on the same location.

Thank you

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My giess is Jolla cant cache the files because phone would soon encounter the btrfs balance bug.

alloj ( 2015-04-08 10:24:43 +0300 )edit

Ouch... ;-D

lispy ( 2015-04-08 10:37:51 +0300 )edit

so what should I do? My old jolla (it has been replaced by care) never had filesystem issues

c.la ( 2015-04-08 13:33:42 +0300 )edit

Maybe it help IF you put big sdcard in Jolla?

alloj ( 2015-04-08 14:12:50 +0300 )edit
4

I'll just note that modRana caches map tiles by default. :)

MartinK ( 2015-04-08 14:58:22 +0300 )edit

2 Answers

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answered 2015-04-17 06:12:26 +0300

Aaron McCarthy gravatar image

Sailfish Maps currently has a fixed 100MB tile cache. One of the reasons for the limit is that there is currently no mechanism for clearing the cache when storage space gets low.

There is no interval for redownloading tiles. However the most recent version is always used. When the tile version on the server is updated it does cause Sailfish Maps to not use the old versions in the tile cache.

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what tiles are cached? THe first ever 100MB of them or the latest 100MB (like in a circular buffer, older ones get overwritten)?

Because if it's the latter (circular buffer) then my jolla maps app doesn't behave as such.

c.la ( 2015-04-24 09:18:28 +0300 )edit

@cla All tiles are cached, the least recently used tiles are removed when new tiles is downloaded.

Aaron McCarthy ( 2015-10-30 03:18:36 +0300 )edit
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answered 2015-04-08 22:30:58 +0300

I have no explanation for any perceived change in caching, but in there's at least three possible reasons for lack of caching in general.

  1. sailfish-maps uses QtLocation, which seems to be very eager to redownload tiles. QtLocation apparently hasn't been designed to work in any sensible predefined way when offline or to minimize tile downloads.

  2. Whatever deal Jolla has with HERE might force them redownload tiles at some interval specified by HERE. Commercial map tile providers usually want make sure you have the latest data, even if you don't care about it.

  3. Current Btrfs trouble on the Jolla phone make unlimited caching dangerous. If your data use has been "about 1,2-1,5 GB", that means a seriously huge amount of tiles -- probably over 100,000. Even if caching would be limited by total file size or age and even if you have space left, with a 100,000 tiles you'd be likely to hit the Btrfs metadata limits.

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Asked: 2015-04-08 09:20:10 +0300

Seen: 459 times

Last updated: Apr 17 '15