How to generate unique Auto increament id field across multiple data centers
If you are using replication to 'replicate' data between the different data centers then you can use something like:

auto_increment_increment=3

auto_increment_offset=1 #data center 1

auto_increment_offset=2 #data center 2

auto_increment_offset=3 #data center 3

which will then offset the auto increment accordingly. e.g. 

data center1 - 1, 4, 7

data center2 - 2, 5, 8

data center3 - 3, 6, 9