问题
How can we generate unique id's between two JVMs running at the same time?
I think UUID uuid = UUID.randomUUID(); or UID uid = new UID(); is not enough.
回答1:
You can concat to UUID server ID so UUID will be unique in all servers
回答2:
See UUID docs, you can follow the link to find the rfc4122 explaining how the UUID will be generated. The last 48 bits are concerning your question, the spacial unique node identifier confirming that this value will be a Universally Unique IDentifier.
4.1.2. Layout and Byte Order
To minimize confusion about bit assignments within octets, the UUID
record definition is defined only in terms of fields that are
integral numbers of octets. The fields are presented with the most
significant one first.
Field Data Type Octet Note
#
time_low unsigned 32 0-3 The low field of the
bit integer timestamp
time_mid unsigned 16 4-5 The middle field of the
bit integer timestamp
time_hi_and_version unsigned 16 6-7 The high field of the
bit integer timestamp multiplexed
with the version number
clock_seq_hi_and_rese unsigned 8 8 The high field of the
rved bit integer clock sequence
multiplexed with the
variant
clock_seq_low unsigned 8 9 The low field of the
bit integer clock sequence
node unsigned 48 10-15 The spatially unique
bit integer node identifier
The only risk I can see come from that part
A UUID is an identifier that is unique across both space and time, with respect to the space of all UUIDs. Since a UUID is a fixed size and contains a time field, it is possible for values to rollover
But this would need to run for a long time before it come to you. So, I would not be worried to much with you current solution.
来源：https://stackoverflow.com/questions/44882649/how-to-generate-unique-id