Re: all python threads hung

dcharno wrote:
> I have a number of threads which collect and queue data.  A separate 
> thread inserts the queued data in to an sqlite database.  Another thread 
> services network requests for statics from the database.
>
> The problem I have is long periods of time where all threads in the app 
> appear to be hung. I've found that the duration of the 'stall' is always 
> a multiple of the pysqlite timeout I've set -- typically 2x or 3x.  My 
> timeout was set to 20seconds, but none of the database transactions are 
> longer than 200ms.
>
> At most, I'd expect my two threads to hang.  I'm not understanding how 
> all the threads in the system could be effected.  Any thoughts would be 
> greatly appreciated.
>   

It's quite easy to get pysqlite threads blocking each other (see #126 
[1] for more about that).
If in addition, one of the blocked thread is also holding a Lock (the 
one protecting concurrent access to your queue?), then any other thread 
trying to acquire that lock will get blocked as well.

Hope this helps,

-- Christian

[1] - http://www.initd.org/tracker/pysqlite/ticket/126