"""
We patch uuid.uuid1() to take a random `node` (used to be the 48 bit MAC
address) according to RFC 4122 section 4.5 and CSPRNG 14 bit `clockseq`
See: https://docs.python.org/2/library/uuid.html#uuid.uuid1
and https://svn.python.org/projects/python/branches/release27-maint/Lib/uuid.py
and https://tools.ietf.org/html/rfc4122#section-4.5

The primary use-case for a UUID like this is to guarantee a virtually
collision-free monotonically-increasing value (based on the clock) such
that it can replace an object like an 'autoincrementing' integer primary
key field in a database that plays nicely with clustered indexing.
"""

from random import SystemRandom
from uuid import uuid1 as _uuid1

def uuid1(node=None, clockseq=None):
    if node is None:
        node = SystemRandom().randrange(0, 1<<48) | 0x010000000000
        # according to RFC the LSB of the first octet should be set to 1    
    if clockseq is None:
        clockseq = SystemRandom().randrange(1<<14) 
    return _uuid1(node, clockseq)