Re: advisability of closing long-running ZEO connection

On Thu, Nov 10, 2016 at 12:21 PM, Boylan, Ross <[email protected]> wrote:

> Thanks for your response. See below in blue:
> ------------------------------
> *From:* [email protected] [[email protected]] on behalf of Jim Fulton [
> [email protected]]
> *Sent:* Thursday, November 10, 2016 6:40 AM
> *To:* Boylan, Ross
> *Cc:* zodb ‎[[email protected]]‎
> *Subject:* Re: [ZODB] advisability of closing long-running ZEO connection
>
> I assume/hope that your subject is erroneous.  I assume you're referring
> to ZODB connections, not ZEO connections.
>
> From the client I do
> db = ZEO.DB(dbname)
> and then, in each thread,
> conn = db.open()
>

OK, so my assumption is correct. These are ZODB connections, not ZEO
connections.



> On Wed, Nov 9, 2016 at 3:56 PM, Boylan, Ross <[email protected]> wrote:
>
>> My application sets up a lot of objects and the does a commit, with ZEO
>> providing the backend.
>> It then runs a lot of computations in threads, each of which updates the
>> data at the start and the end of the computation.
>>
>
> Do these computations use the database data while the computations are
> underway?
> No.  The computation threads just spawn off a SAS process and wait for it
> to finish.
>

OK. Unless the updates at the beginning and end need to be in the same
transaction, I'd recommend opening a connection to make each change and
then closing it after the commit. In other words, at the beginning of the
thread, open a connection, do whatever and then close it. Then at the end
of the thread, open a new connection for that work. But I don't really know
what you're doing so I may be off base.



> My application's main thread does nothing during this time except launch
>> new threads, and all the information it needs is in the objects as of the
>> first commit.
>>
>> Is it safe to close the connection in the main thread during this time?
>> My concern is that some of the objects I need may dematerialize if I do so
>> (or perhaps might have been dematerialized while the connection was open).
>>
>
> You should **never** hold on to objects from closed connections.
> That's what I needed to know.
>

Cool.

Jim

-- 
Jim Fulton
http://jimfulton.info

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