for db(status == 'pending').select():
task.update_record(status == 'processing')
success = do_long_thing_with(task)
fail
if success:
task.update_record(status = 'done')
This way, records that have a status of processing will not get pulled
in by a concurrent thread.
-Thadeus
On Tue, Dec 29, 2009 at 1:07 AM, toomim <[email protected]> wrote:
> What's the best way to use web2py to process a queue of data in a cron
> job without race conditions?
>
> My code basically does this:
>
> for task in db(status != 'done').select():
> success = do_long_thing_with(task) # takes a long time, might
> fail
> if success:
> task.update_record(status = 'done')
>
> I launch this every N minutes in a cron job. But if it takes more
> than N minutes to run, the cron starts another loop in parallel and
> duplicates all calls to do_long_thing_with(task).
>
> What's the best way to fix this? It seems hard without being able to
> manually say where transactions should start with BEGIN.
>
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