Re: objects added via ZEO ClientStorage not making it into the DB

Thanks for the threading tip.  Once I managed to suppress all existing 
ClientStorage instances before running multiprocessing.Process, things 
worked.  Any other state like that I have to worry about?

Bill

On Saturday, April 23, 2016 at 6:41:37 AM UTC-7, Marius Gedminas wrote:
>
> On Fri, Apr 22, 2016 at 09:51:01AM -0700, Bill Janssen wrote: 
> > I'm seeing missing objects. 
> > 
> > Here's my scenario.  Python 2.7.11 on Ubuntu 15 (and 16), ZODB 4.2, ZEO 
> > 3.7.0b3.  I start a parent process; it sets up a ZEO server, then uses 
> > multiprocessing.Process to start a child process.  The child uses 
> > ClientStorage to connect to the server, then adds an object. 
>
> Multiprocessing uses os.fork() a lot.  You need to be very careful about 
> that: ClientStorage relies on a dedicated communication thread to talk 
> to the ZEO server, and os.fork() kills all the threads in the child 
> process (except for the one calling os.fork()).  Things should work fine 
> if the communication thread is created *after* the fork, but things will 
> break badly if the thread is created before the fork. 
>
> You can use threading.enumerate() at the point where you're doing the 
> transaction.commit() in your child process to take a look at all the 
> threads and see if the ZEO communications thread is among them. 
>
> HTH, 
> Marius Gedminas 
> -- 
> All programs have at least one bug remaining and can be optimized by one 
> byte. 
> Thus, by mathematical induction, all programs can be reduced to one byte. 
> And 
> it won't work. 
>

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