Java 11 Support Preview is available in Jenkins 2.155+

As you probably remember, in June 2018 we had an online hackathon targeting Java 10+ support in Jenkins. As a part of the hackathon, we provided the experimental support of Java 11. This event was a big success for us, and we were able to get Jenkins running with Java 10 and 11-ea, including major features like Jenkins Pipeline, JobDSL, Docker/Kubernetes plugins, Configuration as Code, BlueOcean, etc. It gave us confidence that we can provide Java 11 support in Jenkins without major breaking changes. After the hackathon, Oleg Nenashev created JEP-211: Java 10+ support in Jenkins (was later adjusted to target Java 11 only). Platform Special Interest Group has been also founded to coordinate the Java 11 support work and other platform support efforts (packaging, operating system support, etc.).

A group of contributors continued working on Java 11 support, mostly focusing on upstreaming functional patches, enabling Java 11 support in development tools, testing and addressing known compatibility issues. See the Platform SIG meeting notes for detailed status updates. Starting from Jenkins 2.148, Jenkins successfully runs with latest OpenJDK 11 releases on various Linux and Windows platforms. We performed a LOT of automated and exploratory tests, Jenkins plugins appear to work well with some exceptions (see below). There is ongoing test automation effort towards the GA releases, but we were able to successfully run Jenkins core tests, full Acceptance Test Harness, and Plugin Compat Tester for recommended plugins. We also deployed a temporary Experimental Update Center for Java 11 which allows quickly delivering fixes for Java 11 early adopters. Jenkins 2.155+ defaults to this update center when running with Java 11, and that’s why we announce preview availability for this version.

On Nov 19, 2018 we presented the current Java 11 support status at the Platform SIG meeting slides, and we agreed that we would like to proceed with the preview availability so that we can offer something for evaluation to Jenkins users. By the next meeting on Dec 04, all blockers have been addressed, and the Platform SIG meeting signed off the Java 11 preview availability.

Starting from Jenkins 2.155, we provide Docker images for the Jenkins controller and agent. All these images are based on the official openjdk:11-jdk image maintained by the Docker Community. There were discussions about migrating to other base images, but we decided to exclude it from the Preview Availability scope. Similarly, we do not provide Alpine images for now.

Running without Docker is not that trivial, because Jenkins depends on some modules which have been removed from Java 11. We plan to address it in the General Availability release somehow (see JENKINS-52186), but for now some manual actions are required to run Jenkins WAR with Java 11.

To help users to track down the compatibility issues, we have created a new Known Java 11 Compatibility Issues Wiki page.

Several important issues and obstacles:

We also know about some minor incompatibilities in other plugins, but we do not consider them as blockers for preview availability.

If you discover any Java 11 incompatibilities, please report issues in our bugtracker. Please set java11-compatibility labels for such issues so that they automatically appear on the Wiki page and get triaged.

For the security issues please use the standard vulnerability reporting process. Although we will be fixing Java 11 specific issues in public while it is in the preview, following the security process will help us to investigate impact on Java 8 users.

Once Java 11 support is released, we expect reports of regressions in plugins and Jenkins core. One of the concerns are exotic platforms with native libraries, and of course other Java versions. There is also a risk of 3rd-party library incompatibilities with Java 11. To mitigate the risks, we have created a Java 11 Support Team. This team will be focusing on triaging the incoming issues, helping to review pull requests and, in some cases, delivering the fixes. The process for this team is documented in JEP-211.

We do not expect the Java 11 Support Team to be able to fix all discovered issues, and we will be working with Jenkins core and plugin maintainers to get the fixes delivered. If you are interested to join the team, reach out to us in the Platform SIG Gitter Channel.

We will appreciate any kind of contributions in the Java 11 effort, including trying out Jenkins with Java 11, reporting and fixing compatibility issues.

Whatever you do, please let us know about your experience by sending a message to the Platform SIG mailing list. Such information will help us a lot to track changes and contributions. Any other feedback about the migration complexity will be appreciated!

On Dec 18 (4PM UTC) we will be presenting the Java 11 Preview Support at the Jenkins Online Meetup (link). At this meetup we will summarize the current Java 11 Preview support status. If you are a plugin developer, we will also organize separate sessions about testing plugins with Java 11 and about common best practices for fixing compatibility issues. Please follow the Platform SIG announcements if you are interested.

In the next weeks we will focus on addressing feedback from early adopters and fixing the discovered compatibility issues. We will also continue working on Java 11 support patches towards the general availability next year (JENKINS-51805). In addition to that, we will start working on Java 11 support in subprojects, including Jenkins X and Jenkins Evergreen.