When are you truly forced to use UUID as part of the design?

Question

I don\'t really see the point of UUID. I know the probability of a collision is effectively nil, but effectively nil is not even close to impossible.

Answer 1

I have a scheme for avoiding UUIDs. Set up a server somewhere and have it so that every time some piece of software wants a universally unique identifier, they contact that server and it hands one out. Simple!

Except that there are some real practical problems with this, even if we ignore outright malice. In particular, that server can fail or become unreachable from part of the internet. Dealing with server failure requires replication, and that's very difficult to get right (see the literature on the Paxos algorithm for why consensus building is awkward) and is pretty slow too. Moreover, if all the servers are unreachable from a particular part of the 'net, none of the clients connected to that subnet will be able to do anything because they'll all be waiting for new IDs.

So... use a simple probabilistic algorithm to generate them that is unlikely to fail during the lifetime of the Earth, or (fund and) build a major infrastructure that is going to be a deployment PITA and have frequent failures. I know which one I'd go for.