Question

Let’s say I have a model User with property bands of type StringListProperty. In a request handler, I’m extending/appending to bands list and also I’m creating a lot of tasks for taskqueue, whose handlers will also append to the bands list. Is it possible to have race conditions?

Answer 1

You can use Tasks within Transaction to make sure your tasks are only enqueued if the corresponding Datastore transaction has been committed successfully.

Just add transactional=True keyword arg when adding tasks within a transaction:

taskqueue.add(url='/path/to/my/worker', transactional=True)