If you get a UUID collision, go play the lottery next.
From Wikipedia:
Randomly generated UUIDs have 122 random bits. Out of a total of 128
bits, four bits are used for the version (‘Randomly generated UUID’),
and two bits for the variant (‘Leach-Salz’).With random UUIDs, the
chance of two having the same value can be calculated using
probability theory (Birthday paradox). Using the approximation
p(n)\approx 1-e^{-\tfrac{n^2}{{2x}}}these are the probabilities of an
accidental clash after calculating n UUIDs, with x=2122:n probability
68,719,476,736 = 236 0.0000000000000004 (4 × 10−16)
2,199,023,255,552 = 241 0.0000000000004 (4 × 10−13)
70,368,744,177,664 = 246 0.0000000004 (4 × 10−10)To put these numbers into perspective,
the annual risk of someone being hit by a meteorite is estimated to be
one chance in 17 billion, which means the probability is about
0.00000000006 (6 × 10−11), equivalent to the odds of creating a few tens of trillions of > UUIDs in a year and having one duplicate. In
other words, only after generating 1 billion UUIDs every second for
the next 100 years, the probability of creating just one duplicate
would be about 50%. The probability of one duplicate would be about
50% if every person on earth owns 600 million UUIDs.