I had issues with Pharo not being random during the first startup: http://forum.world.st/Random-is-not-random-at-startup-td4895905.html
Even though the seed is different during startup, the mask trims the randomness away. Looking at NeoUUID, it actually makes it worse on Linux (and presumably Unix/Mac too), because it uses Pharo's broken seeding and not pooling /dev/urandom. (I can test it on linux machine later today just to be sure.) > Still, UUIDs are not 100% guaranteed to be unique, they are a (very good) > best effort. For all intents and purposes they are considered 100% to be unique. If you generate two identical V4 UUIDs then either PRNG or seeding is broken (seeding in Pharo's case). Peter On Mon, Feb 06, 2017 at 02:35:37PM +0100, Sven Van Caekenberghe 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 > > > > >
