When should I use uuid.uuid1() vs. uuid.uuid4() in python?

Question

I understand the differences between the two from the docs.

uuid1():
Generate a UUID from a host ID, sequence number, and the current time

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Answer 1

My team just ran into trouble using UUID1 for a database upgrade script where we generated ~120k UUIDs within a couple of minutes. The UUID collision led to violation of a primary key constraint.

We've upgraded 100s of servers but on our Amazon EC2 instances we ran into this issue a few times. I suspect poor clock resolution and switching to UUID4 solved it for us.