Looking ahead: proposed Hg forest consolidation for JDK 10
joe.darcy at oracle.com
Tue Oct 11 02:11:43 UTC 2016
Looking ahead to JDK 10, a group of JDK engineers have been exploring
consolidating the large number of Hg repositories in an open JDK forest
to a single one with the goal of using the consolidated arrangement for
This message is being sent to jdk9-dev since a jdk10-dev alias to
discuss JDK 10 doesn't exist yet.
A JEP describing the project has been submitted :
JDK-8167368: Consolidate JDK 10 OpenJDK repositories to a single
The text of the JEP describes the motivation and current state of the
work in more detail, including proposed changes to the file layout.
Publication of the prototype consolidated repository is planned, but not
done yet. The email below has a list of additional anticipated questions
We feel this consolidated arrangement offers some significant structural
advantages for managing the JDK's source code and we are now asking for
feedback on this potential change. In particular, if you feel there is a
show-stopper problem with making this change, please let us know!
I'd like to acknowledge the work of Stefan Sarne, Stuart Marks, and
Ingemar Aberg participating in discussions leading up to the prototype
and I'd like to especially recognize the contributions of Erik Helin for
savvy Hg manipulations and Erik Joelsson for skillful build wrangling in
Please send initial comments by October 18, 2016.
Q: What about the set of forests for JDK 10? Are we going to have
master, dev, client, hotspot, etc. the same set as in 9?
A: That is a separate question from the repository consolidation, but
there will likely be simplifications here too. Discussions on that point
will come later.
Q: I usually just build the code in repo X today. Will I have have to
build the *whole JDK* now?
A: Not necessarily. The same top-level build targets should work in the
Q: Does disk usage change?
A: The total disk usage of the current forest compared to the
consolidated forest is nearly the same.
Q: In more detail, how were the changesets imported?
A: The scripts used for the consolidation conversion are attached to the
Q: What happens to the Hg hashes?
A: The conversion scheme used in the prototype does *not* preserve Hg
hashes of changesets compared the current forests. However, the bug ids
are preserved and can be searched for. In addition, one or more
pre-consolidation forests should be archived in perpetuity so that URLs
in bug comments continue to work, etc.
A mapping of the old hashes to the corresponding new hashes might be
generated and placed in the final new repo.
Q: I'm allergic to tabs; what about jcheck?
A: If history is preserved, the checking done by jcheck needs to be
modified for the consolidated forest. One way to do this is to augment
the white lists used in jcheck with the conflicting changesets. This
approach may not be elegant, but it is effective and doesn't appear to
appreciably impact jcheck running times.
Q: Will the future 9 update forest also have this consolidation
A: The script used to do the consolidation conversion is deterministic
and could be run to create the 9 update forest in the future at the
discretion of the 9 update team.
Q: For backports for forwardports, will there be a script to translate
patch files across the consolidation boundary?
A: That work is planned, but not yet done; see JDK-8165623: Create patch
translator to update paths pre/post consolidation.
Q: It's the 21st century and I develop using an IDE. That is still going
to work, right?
A: The prototype to date does include updating the various IDE support
files, but bug JDK-8167142 has been filed to track that work.
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