JSON serialization error in admin view when using PickleEncoder

[huubbouma]

If you use the PickleEncoder for the serialization of the arguments to actors:

DRAMATIQ_ENCODER = "dramatiq.PickleEncoder"

Then an error will appear if you go to the task details in the admin interface: TypeError: Object of type Application is not JSON serializable

[amureki]

Hey @huubbouma, thanks for the bug report!

I am trying to reproduce this issue; In my simple test, everything worked fine when I switched encoder:

I guess, I am lacking your context. May you share what your actor looks like? I see that type error complains about Application, what is it, Django model?

In general, according to best practices of working with queues (Dramatiq, Celery, regardless of which one) it is important to pass to actors as simple data (arguments) as possible: https://dramatiq.io/best_practices.html#simple-messages

So, for example, instead of passing User object to change its email in a task, I'd recommend passing user_id, so the task can do a query to the database to access and change it. This way we are improving performance (as less data needs to go through the queue) and we are also protected from race conditions (if something will change User object while the task is in the queue, it would mean, task will operate with an outdated object and might overwrite new changes).

But please, correct me if my understanding of your context is wrong, I am happy to hear more to be able to reproduce it.

[huubbouma]

You're absolutely correct and we should use simple data, but my issue is that I'm migrating a hug codebase from another task queue and I don't have the the time now to convert existing code. In my example we have django objects in the kwargs, which are not serializable.