The "post_comment" example of sessions appears to be incorrect: https://docs.djangoproject.com/en/3.1/topics/http/sessions/#examples
Imagine two HTTP requests coming in at the same time, both seeing that "has_commented" is False, and then both create a comment and set the session variable to True. I just experienced this issue myself, which is why I bring it up. I would offer to update the documentation...but I'm struggling to come up with a way to actually make this pattern work with sessions! Assuming there are other views that update other variables in the session, it seems like you must lock the session when you read it (i.e. "SELECT...FOR UPDATE"). So anything that reads or writes to the session must be wrapped in an atomic block. I think it might be useful to add a method to support locking the session before any reads/writes. Or maybe we should just update the docs to warn people about how race prone sessions are? Any thoughts? -- You received this message because you are subscribed to the Google Groups "Django developers (Contributions to Django itself)" group. To unsubscribe from this group and stop receiving emails from it, send an email to django-developers+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/django-developers/89941f4b-61a2-446e-ba72-dfe428e0a9dbn%40googlegroups.com.
