> On 6 Feb 2017, at 15:21, Yuriy Tymchuk <yuriy.tymc...@me.com> wrote: > > Of course UUID is not guaranteed to be absolutely random. But it is > suspicious these similarities happen is a small timeframe, so I think that > the image got restarted a few times, but generated the same ID.
If you say a timestamp is more reliable in your use case, note that NeoUUID contains a ms clock value, so it should not be possible that you get 2 similar values for 2 distinct runs. If you are limited to macOS/Linux one can always do '/dev/random' asFileReference binaryReadStreamDo: [ :in | in next: 8 ]. to get random bytes. > Uko > > >> On 6 Feb 2017, at 14:35, Sven Van Caekenberghe <s...@stfx.eu> wrote: >> >> >>> On 6 Feb 2017, at 14:17, Yuriy Tymchuk <yuriy.tymc...@me.com> wrote: >>> >>> Hi everyone, >>> >>> I’m using the session id (Smalltalk session id) for my data recording, so I >>> can distinguish if the recorded events came from the same session. The idea >>> is that each time an image is started a new session is created and assigned >>> a new UUID. Now when I started to look on the data I noticed that I have >>> some cases where I have same session IDs with different session creation >>> times (yes a new session is initialized with a current timestamp). The time >>> difference for the sessions with the same UUID and a different timestamp is >>> within 2 hours. Then another thing that I did is to group the data by the >>> timestamp and there are no cases where I have a different ID for the same >>> timestamp, which shows that the timestamp is a more reliable ID. Now I will >>> deal with my data just fine, but maybe we need to look in the >>> implementation why do we get sessions with the same IDs? >>> >>> Cheers. >>> Uko >> >> I would be very surprised it would happen with NeoUUIDGenerator >> (NeoUUIDGenerator next). The idea was to replace UUIDGenerator and the VM >> plugin by it. That got stalled when there was unforeseen interaction with >> WorkingSession. I believe that should be solved by now. >> >> Still, UUIDs are not 100% guaranteed to be unique, they are a (very good) >> best effort. >> >> But I agree that if they repeat in such a short time frame, that should be >> considered a bug. >> >> Sven >> >> >> >> >> > >
