Comment by ffsm8
8 hours ago
> your side effects (e.g. database writes) aren't idempotent
What does idempotent mean in this context, or did you mean atomic/rollback on error?
I'm confused because how could a database write be idempotent in Django? Maybe if it introduced a version on each entity and used that for crdt on writes? But that'd be a significant performance impact, as it couldn't just be a single write anymore, instead they'd have to do it via multiple round trips
In the context of background jobs idempotent means that if your job gets run for a second time (and it will get run for a second time at some point, they all do at-least-once delivery) there aren't any unfortunate side effects to that. Often that's just a case of checking if the relevant database updates have already been done, maybe not firing a push notification in cases of a repeated job.
In my experience async job idempotency is implemented as upserts. Insert all job outputs on the first run. Do (mostly) nothing on subsequent runs. Maybe increment a counter or timestamp.