[MapProxy] FYI: Possible root cause of 'sqlite3.OperationalError: database is locked'

Oliver Tonnhofer olt at omniscale.de
Tue Mar 17 02:39:32 PDT 2015

Hi Just,

> On 16.03.2015, at 14:33, Just van den Broecke <just at justobjects.nl> wrote:
> I begin to suspect that USLEEP is not the cause here but the underlying filesystem. I've found other causes of this error when an sqlite db is on a networked filesystem like NFS, CIFS/Samba. Several refs found and http://sqlite.org/faq.html#q5. Not a good idea anyway, but it hinted me to look into that direction.

Yes, I think USLEEP is only one cause. It even fails on my system if I put enough pressure on SQLite (500 single inserts/s are still working).

Here is a small test script: https://gist.github.com/olt/fcef7445657be3b60682
You can change the number of concurrent writers or the number of “tiles” for each writer and a "process delay". 


Oliver Tonnhofer  | Omniscale GmbH & Co KG  | http://omniscale.com
OpenStreetMap WMS and tile services         | http://maps.omniscale.com

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