> A "tasks fired by tasks" is a perfect example: what if you want to queue > your tasks only if the "parent" completed correctly ?
This makes perfect sense. Also I forget that the "message passing" is being done through the database. I added a db.commit() at the end of the parent task and all is right with the world. You're saving my life today! Thanks, Dean On Wednesday, April 24, 2013 5:14:46 PM UTC-4, Niphlod wrote: > > you're probably missing the part where a task gets executed in a > "shell-like" environment, whose most-notable difference is that you have to > manually db.commit(). > > While a db.commit() is ensured "automatically" at the end of every request > in the normal web environment by web2py, inside a task you may want to > commit() or rollback() "as per requirements". > > That's the reason why queue_task() doesn't enforce a db.commit() .... in a > normal environment your task queued by the "web" is committed only if there > aren't exceptions. Perfect! (you don't want to queue tasks if the > controller function that generated it threw an exception) > > A "tasks fired by tasks" is a perfect example: what if you want to queue > your tasks only if the "parent" completed correctly ? > > e.g. > > def parent_task(): > ... do_something > ... queue_task(child_task, ...) > 1/0 > ...whoopsie! > > def child_task(): > """I must run only if parent_task() completed correctly""" > ... do_something() > > so, just db.commit() at the end of parent_task and you're good to go. > > PS: restating over and over (in case it's not clear). Whatever you do in > your tasks involving a database must be commit()ed. This involves queueing > new tasks cause you're using the database to queue them. > > On Wednesday, April 24, 2013 5:14:46 PM UTC-4, Niphlod wrote: > > you're probably missing the part where a task gets executed in a > "shell-like" environment, whose most-notable difference is that you have to > manually db.commit(). > > While a db.commit() is ensured "automatically" at the end of every request > in the normal web environment by web2py, inside a task you may want to > commit() or rollback() "as per requirements". > > That's the reason why queue_task() doesn't enforce a db.commit() .... in a > normal environment your task queued by the "web" is committed only if there > aren't exceptions. Perfect! (you don't want to queue tasks if the > controller function that generated it threw an exception) > > A "tasks fired by tasks" is a perfect example: what if you want to queue > your tasks only if the "parent" completed correctly ? > > e.g. > > def parent_task(): > ... do_something > ... queue_task(child_task, ...) > 1/0 > ...whoopsie! > > def child_task(): > """I must run only if parent_task() completed correctly""" > ... do_something() > > so, just db.commit() at the end of parent_task and you're good to go. > > PS: restating over and over (in case it's not clear). Whatever you do in > your tasks involving a database must be commit()ed. This involves queueing > new tasks cause you're using the database to queue them. > > On Wednesday, April 24, 2013 5:14:46 PM UTC-4, Niphlod wrote: > > you're probably missing the part where a task gets executed in a > "shell-like" environment, whose most-notable difference is that you have to > manually db.commit(). > > While a db.commit() is ensured "automatically" at the end of every request > in the normal web environment by web2py, inside a task you may want to > commit() or rollback() "as per requirements". > > That's the reason why queue_task() doesn't enforce a db.commit() .... in a > normal environment your task queued by the "web" is committed only if there > aren't exceptions. Perfect! (you don't want to queue tasks if the > controller function that generated it threw an exception) > > A "tasks fired by tasks" is a perfect example: what if you want to queue > your tasks only if the "parent" completed correctly ? > > e.g. > > def parent_task(): > ... do_something > ... queue_task(child_task, ...) > 1/0 > ...whoopsie! > > def child_task(): > """I must run only if parent_task() completed correctly""" > ... do_something() > > so, just db.commit() at the end of parent_task and you're good to go. > > PS: restating over and over (in case it's not clear). Whatever you do in > your tasks involving a database must be commit()ed. This involves queueing > new tasks cause you're using the database to queue them. > > -- --- You received this message because you are subscribed to the Google Groups "web2py-users" group. To unsubscribe from this group and stop receiving emails from it, send an email to web2py+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/groups/opt_out.
