JDK 21 enters Rampdown Phase One next Thursday

[Mark Reinhold]

JDK 21 enters Rampdown Phase One next week on Thursday, 8 June.
Changes intended for JDK 21 should be in the main-line repository
(https://github.com/openjdk/jdk) by 16:00 UTC on that day [1].

At that time we’ll fork the main line to the JDK 21 stabilization
repository, jdk21, and promote next week’s build and all remaining
JDK 21 builds from there.

In contrast to past practice, in this release we will integrate most
stabilization changes via backports.

  - Most fixes and enhancements intended for the stabilization repository
    will also be applicable to the main-line repository.  Integrate such
    a change into the main-line repository first.  Then, after you have
    obtained any required approvals, backport it to the stabilization
    repository using the Skara `/backport` command [2] or, if necessary,
    by manually opening a backport PR with the title `Backport $HASH`,
    where `$HASH` is the original commit hash.  (The Developers’ Guide
    contains more information on working with backports [3].)

  - Some fixes will be specific to the stabilization repository and not
    applicable to the main-line repository.  Integrate such a change
    directly into the stabilization repository.

In order to make sure that no backports are missed, prior to the RDP 2
and RC phases JDK Contributors will be reminded to review changes that
have been integrated into the main-line repository but not backported
to the stabilization repository.

The Rampdown Phase One process is defined in JEP 3 [4], which has been
updated to describe the new stabilization-via-backports idiom.

To answer a potential FAQ, one more time: Now that we’ve moved over
to Git, why don’t we just use a branch in the main-line repository for
JDK 21 stabilization work?  A few of us have given that some thought,
but a change of that scope requires a fair amount of preparation and
coordination.  We hope to revisit that option for JDK 22.

- Mark


[1] https://time.is/1600_8_June_2023_in_UTC/Stockholm/London/Boston/San_Francisco?JDK_21_Rampdown_Phase_One
[2] https://wiki.openjdk.org/display/SKARA/Backports
[3] https://openjdk.org/guide/#working-with-backports-in-jbs
[4] https://openjdk.org/jeps/3