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java-11-openjdk as system JDK in F33

Summary

Update the system JDK in Fedora from java-1.8.0-openjdk to java-11-openjdk.

Owner

  • Name: Jiri Vanek
  • Email: <jvanek@redhat.com>
  • Product: java and java stack
  • Responsible WG: java-sig (java and java-maint)


Current status

  • Targeted release: Fedora 33
  • Last updated: 2020-03-30
  • FESCo issue: <will be assigned by the Wrangler>
  • Tracker bug: <will be assigned by the Wrangler>
  • Release notes tracker: <will be assigned by the Wrangler>

Detailed Description

Fedora currently ships:

  • java-1.8.0-openjdk (LTS)
  • java-11-openjdk (LTS)
  • an java-latest-openjdk (on jdk14, STS).

where the version-less java and javac (and friends) are provided by java-1.8.0-openjdk.

So every package honoring the packaging rules and requiring java , java-headless or java-devel is built in koji by java-1.8.0-openjdk-devel and pulls java-1.8.0-openjdk(-headless) in runtime (See java ). Also javapackaging-tools are using java-1.8.0-openjdk as hardcoded runtime (see changes)

Debian already moved to JDK11 as system JDK, and in Fedora community we can hear for last two years increasing voices for jdk11 to become the system one. And apparently the java stack is really quite ready for JDK11. Fedora is considered to be bleeding edge distribution, so we should move forward, however JDK11 is not 100% compatible with JDK8, so there may rise nasty issues and very unhappy users.

Major incompatibility is in encapsulation. What was private, is now really private and if one was using it (and it was common) then the code will stop working. Unluckily, most of those issues are not only build time issues, but runtime issues, so hard to spot without proper test coverage.

A bit of history to recall:

version (upstream support) - fedora state

  • Java SE 6 (LTS 2006-cca2014) - added as techpreview in F8 replaced GCJ around F13. See https://fedoraproject.org/wiki/Releases
  • Java SE 7 (LTS 2011-2020(?)) - entered Fedora as tech preview around F16/17 replaced JDK 6 as System JDK in F17
  • Java SE 8 (LTS 2014-2026(???)) - entered Fedora as tech preview in F19 replaced JDK 7 as System JDK in F21. JDK6 and JDK7 later returned as community driven java-1-{6,7}-0-openjdk-legacy packages for a while
  • Java SE 9 (2017-2018) - entered Fedora around F26 as secondary, java-1.9.0-openjdk alongside java-1.8.0-openjdk
  • Java SE 10 (2018-2019) - entered F28 as secondary, java-latest-openjdk alongside java-1.8.0-openjdk
  • Java SE 11 (LTS 2018-??) - entered Fedora as tech preview in F29 together with java-latest-openjdk and java-1.8.0-openjdk
  • Java SE 12 (2019) - updated java-latest-openjdk transparently and keept going alongside java-1.8.0-openjdk and alongside java-11-openjdk
  • Java SE 13 (2019-2020) - updated java-latest-openjdk transparently and keept going alongside java-1.8.0-openjdk and alongside java-11-openjdk
  • Java SE 14 (March 2020-2021(?)) - is updating java-latest-openjdk transparently and will continue to live next to any system JDK(s)
  • Java SE 15 (2020(?)-2021(?)) - will update java-latest-openjdk transparently and will continue to live next to any system JDK(s)
  • Java SE 16 () - will update java-latest-openjdk transparently and will continue to live next to any system JDK(s)
  • Java SE 17 (LTS) - will very likely update java-latest-openjdk transparently and will become future system JDK java-17-openjdk some year later
  • Java SE 18 () - will update java-latest-openjdk transparently and will continue to live next to any system JDK(s)
  • ....

"Political disclaimer"

In previous bumps, we, Red Hat's openjdk team, were a driving force to bump the system JDK. In this case, we are a bit reluctant, but the desire from users to bump the JDK seems strong. We are quite happy to skip JDK11 as system JDK at all, and jump directly from 8 to 17 in some three years.

Benefit to Fedora

JDK11 is out for some time, and most of the bleeding edge distributions already make it default. Most of the projects already adapted new features and make necessary forward-compatible chnages. Although we can can expect some family of packages to remain on jdk8 for ever, the spice should flow

Scope

keep java-1.8-0-openjdk but remove its java/javac versionless provides, make java-11-openjdk providing java, javac and other versionless provides

  • will guarantee fedora to be pure JDK11 distro.
  • will allow maintainers of JDK9 or up incompatible packages to keep using JDK8, however this is just false hope.
    • if such an package depends on package build by JDK11, JDK8 will not be able to pick up that dependency.
    • this may lead to quite a lot of bundling or compat. packages, but may be acceptable
    • people developing JDK8 applications will very likely stay with fedora:)

While quite a lot of users will rejoice, there may be cases where application is very hard to migrate to JDK11, so the contingency plan should be taken very serious.

Other possible approaches already discarded by various discussions

  • java-sig no longer exists
  • as only one option remained in scope, Fesco probably do not need to decide, but still should evaluate, and eventually chnage the way

remove java-1.8-0-openjdk, make java-11-openjdk providing java, javac and other versionless provides

  • will guarantee fedora to be pure JDK11 distro.
  • will force everybody to fix theirs packages for jdk11
    • this may lead to huge orphaning of packages.
  • will guarantee that developers using JDK8 for theirs projects will move to other providers or distros.
  • Jdk8 will very likely appear as community driven legacy package, but its support may be poor.
  • We should keep JDK8 in Fedora for couple of few more years at least as secondary JDK

  • deprecated by discussions

keep java-1.8-0-openjdk, remove its java/javac versionless provides, make java-11-openjdk providing java, javac and other versionless provides, but build in koji (by JDK11) JDK8 compatible bytecode

  • Idea is to provide some kind a koji specific rpm macro, which will add -target 1.8 to all javac calls
    • We are not going to do this via the jdk. We already did once for javadoc in 8, and it was an mistake.
      • Developers developing on Fedora's java-1.8.0-openjdk were then failing to deploy on other plaftorms
    • the change should be koji only
    • maybe enough would be to incorporate this to %mvn call only, and let other build types on default
  • this hybrid approach would make a lot, but needs a lot of cooperation
    • all packages will be able to try to build and run by jdk11 directly
    • packages doomed for jdk8 for ever, will be able to use by jdk11 built dependencies
    • Fedora will not be pure jdk11
    • this is temporary workaround
    • this is untested and without precedent
    • the removal of the macro/target will be another system wide change
  • the macro must be allowed to be disabled, to allow JDK11 specific packages. The usage of -target 8 is killing jdk11 language features
  • this is practically killing any jdk9 and up language features, but for initial mass rebuilding of currently jdk8 comaptible packages, it may be good first step

  • deprecated by discussions

keep java-1.8-0-openjdk, remove its java versionless provides but keep javac versionless provides , make java-11-openjdk providing java, nut not javac versionless provides

  • this will keep javastack build in koji being still built by jdk8, and thus reusable by both JDK8 and 11
  • this will allow both jdk somehow coexists and will allow moreover smooth transition
  • this may cause chaos, once some packages starts to require JDK11 and some JDK8. But that is indirectly threatening all except first case.
  • another disadvantage is possible occurrence of runtime failure, which would otherwise be discovered by building by javac-11

  • not recommended by discusiions

Other

  • Proposal owners:
    • based on above, adapt jdk8 and jdk11 package provides
    • If necessary tune the build environment
  • Other developers:
    • based on selected approach to tune the main build tools
      • at least jpackage-tools and maven will be very likely affected
    • based on selected approach to tune the rpmbuild/macros
    • many java package maintainers will maybe need to adapt theirs packages
      • After the approach is agreed, mass rebuild must be performed
      • FTBFS bugs connected with this proposal, maybe with pagure ticket to allow discussion.
      • Solutions to most common errors should be gathered and published
  • Release engineering: 9347 (a check of an impact with Release Engineering is needed)
    • mass rebuild will be required for this change
  • Policies and guidelines: how to deal with build failures, eventually how to use some jdk11 specific build features will be provided
  • Trademark approval: N/A (not needed for this Change)

Upgrade/compatibility impact

Once the change is implemented properly, the update should be flawless and seamless

How To Test

  • Depends on selected approach, only JRE11 should remain the only system JDK after installing base javastack on clean system
  • Both jdk8 and jdk11 can live togehter on system
  • jdk11 will be selected by default and will run most of the base java stack
  • todo, add few java-package to isntall examples, hopefully for jdk11 only


User Experience

  • Standard user should be still be able to use java stack without even noticing the chnage.
  • Standard developer should be still be able developer any java application comfortably
  • Standard packager will not suffer to much, and should be able to pack any java application for fedora

Dependencies

Around 2600 packages will need attendance 

$ repoquery -q --whatrequires java-headless |wc -l
2481
$ repoquery -q --whatrequires java | wc -l
78
$ repoquery -q --whatrequires java-devel | wc -l
21

Packages needing major work will be

  • java-1.8.0-openjdk
  • java-11-openjdk
  • icedtea-web


Contingency Plan

  • If the mass rebuild, after the change application, breaks to much packages, or some important will be unfixable, jdk8 must be restored back to the position of system jdk.
  • Contingency mechanism: Return jdk8 as system jdk and mass rebuild again. Note, that this may be very hard, because during build of packages by jdk8, by jdk11 built dependencies will be picekd up, so build will fail. Maybe several iterations of mass rebuild will be needed.
  • Contingency deadline: beta freeze
  • Blocks release? Yes
  • Blocks product? N/A
  • Generally going back will be imho impossible. Once the decision is taken, javastack should be fixed, and where it can not be fixed, it had to migrate to compact packages, or bundled-dependencies pacages or be orphaned.

Documentation

Release Notes

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