On Oct 1, 2010, at 9:40 AM, James wrote:
Hi all,
i'm using SQLAlchemy in a TG2 web app which has long-running jobs
kicked off by user POSTs.
I'm planning on writing the pending jobs to the DB, then kick off a
threading.Thread at the end of the web app method to actually do the
work.
Question - I'll need to pass the job description (a SA object) to the
child thread; but to use the description, I need to detach it from the
old TG2 thread's SA session, and reattach it to the child thread's SA
session, right?
How best to do that? I don't see a way of getting the current session
from a live SA object...
If you're writing jobs to the DB anyway, why not use a different process to
handle the jobs, and have it poll the jobs table, instead of passing directly ?
That's how I'm currently doing it. The job runner then forks off additional
procs to run N number of jobs simultaneously with multiprocessing. You at
least get true concurrency that way.
Otherwise, the general paradigm to pass state between threads uses merge(), it
leaves the original unaffected.
obj = Session.query(...).first()
start_new_thread(obj)
# in the thread's method:
def start_my_thing(obj):
obj = Session.merge(obj)
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