问题
Offtopic:
I'm new to stack overflow, and I wanted to say hello!
On topic:
I'm generating a version 5 UUID for an application that needs randomized folder creation and deletion via a timestamp time() through
my $md5_UUID = create_uuid_as_string(UUID_MD5, time."$job");
These folders are generated per run on each job, and are deleted after running. If the same UUID is somehow generated, the +-1000 jobs that are running could halt.
Is there any information that I can pull from this or any possibility of collisions (different data generating the same UUID)? Are they truly unique? Also, which version of UUID should I use between SHA1 and MD5?
回答1:
Use OS Tools
There's probably a pure Perl solution, but it may be overkill. If you are on a Linux system, you can capture the results of mktemp or uuidgen and use them in your Perl script. For example:
$ perl -e 'print `mktemp --directory`'
/tmp/tmp.vx4Fo1Ifh0
$ perl -e '$folder = `uuidgen`; print $folder'
113754e1-fae4-4685-851d-fb346365c9f0
The mktemp utility is nice because it will atomically create the directory for you, in addition to returning the directory name. You also have the ability to give more meaningful names to the directory by modifying the template (see man 1 mktemp); in contrast, UUIDs are not really good at conveying useful semantics.
回答2:
If the folders last only the length of a job, and all the jobs are running on the same machine, you can just use the pid as a folder name. No need for uuids at all.
回答3:
Use a v1 UUID
Perl's time() function is accurate to the second. So, if you're starting your jobs multiple times per second, or simultaneously on separate hosts, you could easily get collisions.
By contrast, a v1 UUID's time field is granular to nanoseconds, and it includes the MAC address of the generating host. See RFC 4122 for details. I can imagine a case where that wouldn't guarantee uniqueness (the client machines are VMs on separate layer-3 virtual networks, all with the same virtual MAC address), but that seems pathologically contrived.
来源：https://stackoverflow.com/questions/17222428/version-5-uuid-in-perl