Are there any reputable libraries (with actual production references like Instagram) to deal with data concurrency, consistency and serializability? A typical scenario is: a race condition caused by two clients. Suppose if someone had two browsers open and simultaneously click on [yes] from browser A and [no] from browser B. I have seen the following 3 things mentioned by doing some google search: 1. use model.objects. select_for_update() with filter() 2. use django-concurrency library ( https://github.com/saxix/django-concurrency) 3. use django-locking (https://github.com/stdbrouw/django-locking) I can't find any production references for #2 and #3. I don't really want to apply some kind lab experiment even though they look good and a quick evaluation seems to do what they advertised. As for #1, I'm thinking about using the following steps: 1. locking on some context object using select_for_update() with filter() within which I check for isOKToUpdate. release lock. If not ok, throw error immediately. 2. updateByClones. I will clone all the objects that I will update then update the clones. 3. locking on the same context object again and check isOKToUpdate again and this time I also do an atomic swap and commit if isOK. release lock. If not ok, throw error also. In short, double locking with atomic swap. The locking is in a transaction with commit_on_ok. The locking block calls should be fairly fast because the context object is light weight with just a hash (some random string) to check whether someone else has updated or not.
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