> With the recent approval of UUIDv7 > (https://datatracker.ietf.org/doc/rfc9562/), this PR aims to add a new static > method UUID.timestampUUID() which constructs and returns a UUID in support of > the new time generated UUID version. > > The specification requires embedding the current timestamp in milliseconds > into the first bits 0–47. The version number in bits 48–51, bits 52–63 are > available for sub-millisecond precision or for pseudorandom data. The variant > is set in bits 64–65. The remaining bits 66–127 are free to use for more > pseudorandom data or to employ a counter based approach for increased time > percision (https://www.rfc-editor.org/rfc/rfc9562.html#name-uuid-version-7). > > The choice of implementation comes down to balancing the sensitivity level of > being able to distingush UUIDs created below <1ms apart with performance. A > test simulating a high-concurrency environment with 4 threads generating > 10000 UUIDv7 values in parallel to measure the collision rate of each > implementation (the amount of times the time based portion of the UUID was > not unique and entries could not distinguished by time) yeilded the following > results for each implemtation: > > > - random-byte-only - 99.8% > - higher-precision - 3.5% > - counter-based - 0% > > > Performance tests show a decrease in performance as expected with the counter > based implementation due to the introduction of synchronization: > > - random-byte-only 143.487 ± 10.932 ns/op > - higher-precision 149.651 ± 8.438 ns/op > - counter-based 245.036 ± 2.943 ns/op > > The best balance here might be to employ a higher-precision implementation as > the large increase in time sensitivity comes at a very slight performance > cost.
kieran-farrell has updated the pull request incrementally with four additional commits since the last revision: - update test - update test - updates - update method to lsb and msb with arraybytes ------------- Changes: - all: https://git.openjdk.org/jdk/pull/25303/files - new: https://git.openjdk.org/jdk/pull/25303/files/c7efd528..33d8ccbf Webrevs: - full: https://webrevs.openjdk.org/?repo=jdk&pr=25303&range=03 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=25303&range=02-03 Stats: 80 lines in 2 files changed: 51 ins; 4 del; 25 mod Patch: https://git.openjdk.org/jdk/pull/25303.diff Fetch: git fetch https://git.openjdk.org/jdk.git pull/25303/head:pull/25303 PR: https://git.openjdk.org/jdk/pull/25303
