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A glimpse of the future

Bruno Verachten
Bruno Verachten
August 30, 2023


You’ve all seen it before: the bitter sting of botched predictions. Flying cars, nuclear ovens in the kitchen, killer robot dogs, and lunar living - all expected to be part of our daily lives by now. Well, some of these wild dreams did come to pass, but I’m not about to roll the dice and predict what our world will look like 50 years hence. Instead, let me paint a picture of Jenkins' future up until October 2024.

Why am I being so specific about this end date, you ask? It’s because I want to highlight two major projects that Jenkins might tackle before the leaves start to fall next year.

One of these projects is the potential leap to JDK21, and we’ve got a proposed roadmap for that. Jenkins will stop supporting JDK 11 in October 2024 when many Java providers (Eclipse Temurin, OpenJDK, …​) stop supporting Java 11. This transition is one of the more significant moves Jenkins might be considering in the coming months.

The next project doesn’t have a roadmap within Jenkins yet, but the progress is promising, and it’s intertwined with the first project like two vines on a trellis. As some of you may know, I’ve got a fondness for CPU architectures that were once seen as outlandish or still raise a few eyebrows. I’m referring to ARM and RISC-V, of course.

ARM is making strides, finding its way into everything from laptops to servers. So, my personal campaign to see ARM recognized as a first-class citizen has been successful.

Now, I’m turning my attention to RISC-V - my next personal endeavor and hobby. While it’s not a fresh face in the CPU crowd, it’s currently experiencing a notable uptick in popularity. The emergence of numerous single-board computers, workstations, and servers reminds me of the early days of ARM, but amplified. I’ve touched on this before in one of my blog posts.

Let’s explore how JDK21, Jenkins, and RISC-V might be connected, at least in the maze of my musings.

Java Version Planning for Jenkins

The ink’s barely dry on the plans for which versions of the JDK the Jenkins project will support this year and the next. What I’m about to spill is just a snippet from a proposal whipped up by Mark Waite. For now, it’s about as definitive as a weather forecast.

There’ll be more detailed blog posts down the line when the final decision is made and the roadmap is as clear as a bell.

Java 11:

  • Java 11 OpenJDK’s public support ends in late 2024.

  • Eclipse Temurin, Red Hat, and Microsoft will support Java 11 through October 2024.

  • Oracle extends support until October 2026.

  • Amazon Corretto supports Java 11 until September 2027.

  • Proposal: End-of-life for Java 11 in Jenkins is suggested for October 31, 2024.

  • Jenkins LTS support for Java 11 will end with the August 7, 2024 release.

  • Java 21 will become the required baseline starting with the September 4, 2024 LTS release.

  • Admin monitors announcing Java 11’s end of life will be enabled in Jenkins weekly releases by October 3, 2023 and in the December 13, 2023 LTS release.

Java 17:

  • Java 17 adoption is increasing in Jenkins. The Jenkins documentation now recommends Java 17 in the installation guides and in the tutorials.

Java adoption rates based on Java version.

Java 21:

  • Java 21 releases on September 19, 2023.

  • Oracle, Eclipse Temurin, Red Hat, and others plan to support Java 21 as a long term support release.

  • Proposal: Jenkins aims to support Java 21 in weekly releases by the end of October 2023.

Are we confident Jenkins will be running on top of JDK 21 next October?
I guess so. Thanks to the work of Stéphane Merle, JDK21 is already available at to build plugins. You just have to add one line to your Jenkinsfile, and your plugin will be tested on JDK21.

configurations: [
[platform: 'linux', jdk: '17'],
[platform: 'linux', jdk: '21'],
[platform: 'windows', jdk: '11']

Furthermore, thanks to the work of the community (and particularly Basil Crow), Jenkins 2.419 and 2.420 no longer require the --enable-future-java flag for JDK 21 beta. Jenkins 2.418 and prior require the flag for Java 21 beta.

$ java -version
openjdk version "21-beta" 2023-09-19
OpenJDK Runtime Environment Temurin-21+34-202308082331 (build 21-beta+34-202308082331)
OpenJDK 64-Bit Server VM Temurin-21+34-202308082331 (build 21-beta+34-202308082331, mixed mode, sharing)

$ java -jar jenkins-2.417.war
Running with Java 21 from /opt/jdk-21, which is not yet fully supported.
Run the command again with the --enable-future-java flag to enable preview support for future Java versions.
Supported Java versions are: [11, 17]
See link: for more information.

$ java -jar jenkins-2.419.war
Running from: /home/mwaite/bugs/jenkins-2.419.war
webroot: /home/mwaite/.jenkins/war
2023-08-24 15:42:32.857+0000 [id=1]     INFO    winstone.Logger#logInternal: Beginning extraction from war file`

I also heard from Basil Crow during the latest Governance board meeting that the Jenkins BOM had already run with JDK21; that’s good news. We will have to stay alert because of things that won’t migrate easily (think of Groovy for example), but if it’s too easy, it’s no fun, right?

Jenkins and RISC-V

The Jenkins project is already churning out aarch64 (64-bit ARM) Docker images for both the controller and agents. On top of that, we’re putting aarch64 through its paces with regular testing, and some parts of the Jenkins infrastructure are already humming along on aarch64 hardware.
We can’t say the same for RISC-V, and for good reason. RISC-V isn’t a supported CPU architecture for Jenkins, it hasn’t been put to the test, Docker isn’t officially on board with this architecture yet (even if Kubernetes is already on the bandwagon), and the Jenkins project doesn’t own a single RISC-V machine.

A few months back, I whipped up a Jenkins agent for RISC-V. Sadly, the machine I had at my disposal wasn’t up to the task of hosting a Jenkins controller. At that time, I was using a nightly build of JDK19 by Temurin.

These days, I’ve got another RISC-V machine that’s got more cores and more memory than the last one, and it meets the Jenkins recommendations, which are:

  • 4 GB+ of RAM

  • 50 GB+ of drive space

Here I’m wielding the StarFive VisionFive2, which boasts 8GB of RAM, 4 RISCV64 cores clocking up to 1.5GHz, and for now, a 128GB SDCard. I’ll swap it out for an NVMe disk when I get around to it. It’s built on the JH7110 from StarFive. We’re seeing this SoC pop up on SBCs more and more these days (Star64, and so on).

Since the machine is (on paper) up to the task of running Jenkins, we should give it a whirl, right?
I loaded a snapshot version of Debian onto the board after giving the firmware a tune-up, and away we went.



The logical first step would be to install a version of the JDK, then follow the official documentation to get Jenkins up and running on Debian, right?

I’ve already been burned by the default JDK on RISC-V with Debian, which turns out to be a Zero VM.
If I were to kick things off with the default JDK, I reckon its performance would leave me so frustrated, I wouldn’t bother going any further.
You’re not buying it? Alright, I see how it is. Let’s not install Jenkins the old-fashioned way then, let’s give it a whirl on the command line after installing the default JDK.

sudo apt install openjdk-17-jdk-headless

java -version
openjdk version "17.0.5" 2022-10-18
OpenJDK Runtime Environment (build 17.0.5+8-Debian-2)
OpenJDK 64-Bit Zero VM (build 17.0.5+8-Debian-2, interpreted mode)

Yes, we’re using a Zero VM. Now onto the Jenkins war download.

curl -L -o /tmp/jenkins.war link:

Let’s launch Jenkins on the command line:

java -jar /tmp/jenkins.war

Running from: /tmp/jenkins.war

webroot: /home/user/.jenkins/war

2023-08-06 12:31:15.432+0000 [id=1] INFO winstone.Logger#logInternal: Beginning extraction from war file

Let’s say I let it run for a good while, and nothing else happened.
A Zero VM is about as useful for running a server as a chocolate teapot.
Let’s switch gears and go with something that’s got a bit more pep in its step.


As I’m penning this article, there’s no official JDK21 release we can snag from the Eclipse Temurin Latest Releases page.
We’ll have to scrounge up a nightly build from the Adoptium Temurin 21 binaries repo.
RISC-V binaries aren’t exactly churned out daily, so you might have to do a bit of digging to find a release with RISC-V binaries.
At the time of writing this blog post, the latest available is release jdk21-2023-08-08-20-16-beta.
In this release, there are several RISC-V binaries up for grabs, but we don’t need static libs or a debug image, so we’ll opt for OpenJDK21U-jdk_riscv64_linux_hotspot_2023-08-08-20-16.tar.gz.

Let’s reel in the JDK21 binaries:

curl -L -O link:

Now that we have them, let’s install them on the machine.

sudo mkdir /opt/jdk21
sudo tar -xzf OpenJDK21U-jdk_riscv64_linux_hotspot_*.tar.gz -C /opt/jdk21 --strip-components=1

Once it’s installed, let’s inform the system about this new set of java binaries:

sudo update-alternatives --install /usr/bin/java java /opt/jdk21/bin/java 1
sudo update-alternatives --install /usr/bin/javac javac /opt/jdk21/bin/javac 1
sudo update-alternatives --install /usr/bin/javadoc javadoc /opt/jdk21/bin/javadoc 1

These commands create alternatives for the java, javac, and javadoc commands and associate them with the respective binaries in the JDK 21 installation.

After installing the alternatives, you need to select the default one. Run the following command and choose the number corresponding to the JDK 21 alternative in the presented menu:

sudo update-alternatives --config java

Repeat this for javac and javadoc:

sudo update-alternatives --config javac
sudo update-alternatives --config javadoc

Verify the Default Java Version: After configuring the alternatives, you can verify that JDK 21 is the default Java version by running:

java -version

Jenkins and JDK21

On the command line

Let’s try to launch Jenkins with JDK21 now, and see if it gets any better than with JDK17:

java -jar /tmp/jenkins.war +
Running from: /tmp/jenkins.war
webroot: /home/user/.jenkins/war
2023-08-24 08:35:11.202+0000 [id=1] INFO winstone.Logger#logInternal: Beginning extraction from war file
2023-08-24 08:35:17.635+0000 [id=1] WARNING o.e.j.s.handler.ContextHandler#setContextPath: Empty contextPath
2023-08-24 08:35:17.947+0000 [id=1] INFO org.eclipse.jetty.server.Server#doStart: jetty-10.0.15; built: 2023-04-11T17:25:14.480Z; git: 68017dbd00236bb7e187330d7585a059610f661d; jvm 21-beta+34-202308081713
2023-08-24 08:35:19.288+0000 [id=1] INFO o.e.j.w.StandardDescriptorProcessor#visitServlet: NO JSP Support for /, did not find org.eclipse.jetty.jsp.JettyJspServlet
2023-08-24 08:35:19.521+0000 [id=1] INFO o.e.j.s.s.DefaultSessionIdManager#doStart: Session workerName=node0
2023-08-24 08:35:22.058+0000 [id=1] INFO hudson.WebAppMain#contextInitialized: Jenkins home directory: /home/user/.jenkins found at: $user.home/.jenkins
2023-08-24 08:35:22.647+0000 [id=1] INFO o.e.j.s.handler.ContextHandler#doStart: Started w.@2a9bc08f\{Jenkins v2.420,/,file:///home/user/.jenkins/war/,AVAILABLE}\{/home/user/.jenkins/war}
2023-08-24 08:35:22.698+0000 [id=1] INFO o.e.j.server.AbstractConnector#doStart: Started ServerConnector@43599640\{HTTP/1.1, (http/1.1)}\{}
2023-08-24 08:35:22.743+0000 [id=1] INFO org.eclipse.jetty.server.Server#doStart: Started Server@b83a9be\{STARTING}[10.0.15,sto=0] @14031ms
2023-08-24 08:35:22.746+0000 [id=35] INFO winstone.Logger#logInternal: Winstone Servlet Engine running: controlPort=disabled
2023-08-24 08:35:23.763+0000 [id=42] INFO jenkins.InitReactorRunner$1#onAttained: Started initialization
2023-08-24 08:35:23.820+0000 [id=40] INFO jenkins.InitReactorRunner$1#onAttained: Listed all plugins
2023-08-24 08:35:28.157+0000 [id=40] INFO jenkins.InitReactorRunner$1#onAttained: Prepared all plugins
2023-08-24 08:35:28.180+0000 [id=40] INFO jenkins.InitReactorRunner$1#onAttained: Started all plugins
2023-08-24 08:35:28.204+0000 [id=40] INFO jenkins.InitReactorRunner$1#onAttained: Augmented all extensions
2023-08-24 08:35:29.182+0000 [id=46] INFO jenkins.InitReactorRunner$1#onAttained: System config loaded
2023-08-24 08:35:29.185+0000 [id=40] INFO jenkins.InitReactorRunner$1#onAttained: System config adapted
2023-08-24 08:35:29.187+0000 [id=43] INFO jenkins.InitReactorRunner$1#onAttained: Loaded all jobs
2023-08-24 08:35:29.194+0000 [id=43] INFO jenkins.InitReactorRunner$1#onAttained: Configuration for all jobs updated
2023-08-24 08:35:29.366+0000 [id=60] INFO hudson.util.Retrier#start: Attempt #1 to do the action check updates server
2023-08-24 08:35:31.242+0000 [id=45] INFO jenkins.install.SetupWizard#init:
Jenkins initial setup is required. An admin user has been created and a password generated.
Please use the following password to proceed to installation:
This may also be found at: /home/user/.jenkins/secrets/initialAdminPassword

Jenkins coughed up this log a few seconds after I fired off the command, so it looks like we’re in business.
Notice anything odd? Shouldn’t Jenkins give us a heads-up that it’s not meant to run with JDK21? Aren’t JDK17 and JDK11 the only ones getting the official nod?
Up until a few weeks ago, that was the score…​ And it’ll stay that way for the LTS versions until next October. At the start of August 2023, this PR got the green light, and since then, there’s no need to add the --enable-future-java flag to give JDK21 versions the go-ahead.

Let’s take the current LTS for a spin:

curl -L -o /tmp/jenkins.war link:
java -jar /tmp/jenkins.war
Running with Java 21 from /opt/jdk21, which is not yet fully supported.
Run the command again with the --enable-future-java flag to enable preview support for future Java versions.
Supported Java versions are: [11, 17]
See link: for more information.

As you can see, the current LTS does not support JDK 21 yet.

Jenkins standard package installation

As we’re using Debian, let’s go with the standard installation of the weekly release now.
Unfortunately, we get an error when installing the Jenkins package the official way.

Job for jenkins.service failed because the control process exited with error code.
See "systemctl status jenkins.service" and "journalctl -xeu jenkins.service" for details.

These commands don’t say much to help with understanding what the problem is.
Let’s try another way:

jenkins: invalid Java version: openjdk version "21-beta" 2023-09-19
OpenJDK Runtime Environment Temurin-21+34-202308081713 (build 21-beta+34-202308081713)
OpenJDK 64-Bit Server VM Temurin-21+34-202308081713 (build 21-beta+34-202308081713, mixed mode, sharing)

Now it’s clear as day: we’ve installed a JDK21 version that plays nice with the WAR file, but the scripts tied to systemd aren’t up to speed with this JDK version yet.
They’re still checking if we’re using JDK11, 17 or 21, but they’re not ready for prime time, hence the failure.
So, how do we fix this mess?

Tweaking the package installation

The official documentation tells us we can override systemd service configurations thanks to

sudo systemctl edit jenkins.

This gives us something like:

### Editing /etc/systemd/system/jenkins.service.d/override.conf
### Anything between here and the comment below will become the new contents of the file

Environment="JAVA_OPTS=-Djava.awt.headless=true -Xmx1024m"

I have just added the last line in the hope of getting Jenkins to start.

sudo systemctl daemon-reload and sudo systemctl start jenkins should now be enough to get Jenkins started.

Yes, we’re almost good to go:

sudo systemctl status jenkins
● jenkins.service - Jenkins Continuous Integration Server
Loaded: loaded (/lib/systemd/system/jenkins.service; enabled; preset: enabled)
Drop-In: /etc/systemd/system/jenkins.service.d
Active: activating (start) since Thu 2023-08-24 09:28:34 UTC; 1min 2s ago
Main PID: 7138 (java)
CPU: 2min 32.701s
CGroup: /system.slice/jenkins.service
└─7138 /usr/bin/java -Djava.awt.headless=true -Xmx1024m -jar /usr/share/java/jenkins.war --webroot=/var/cache/jenkins/war --httpPort=8>

Why almost? We’ve still got a couple of hitches. The first one is the timeout. These RISC-V machines don’t have an optimized kernel yet, so a lot of things are slower than molasses in January. Too slow.
We’d best give Jenkins a bit more time to get its act together, just to be on the safe side.
Let’s bump up the timeout. Like before, we’ll tweak the configuration: courtesy of sudo systemctl edit jenkins.

### Editing /etc/systemd/system/jenkins.service.d/override.conf
### Anything between here and the comment below will become the new contents of the file

Environment="JAVA_OPTS=-Djava.awt.headless=true -Xmx1024m"

### Lines below this comment will be discarded

You may have spotted I removed Environment="JENKINS_OPTS=--enable-future-java" from the settings. We’re running the last weekly release of Jenkins that can handle JDK21, so why should we keep that?
We’ve got another fly in the ointment: the existing jenkins script in /usr/bin/jenkins is pulling a rabbit out of its hat with sed, trying to pin down a valid release. Unfortunately, our Java binary spits out something like “21-beta”. The script then trips up on validation, and in the end, throws a tantrum and refuses to start Jenkins.
Our workaround (while we twiddle our thumbs waiting for this PR to build the next package) is to tweak this file. Change line 40 so it reads:

awk -F '"' '/version/ \{print $2}' | awk -F '.' '\{match($1, /^[0-9]+/); print substr($1, RSTART, RLENGTH)}')

Once you’ve done that, fire off sudo systemctl daemon-reload and sudo systemctl restart jenkins and voilà, you’ve got a Jenkins instance running on JDK21 on a RISC-V machine.
For those of you still hanging in there, yes, there’s a quicker workaround…​
Just stick the Environment="JENKINS_OPTS=--enable-future-java" line back in the override.conf file, and you’ll have a Jenkins instance up and running with JDK21 faster than you can say "compile".


What’s next?

We’ve now got a fresh-off-the-press Jenkins instance humming along thanks to a nightly build of the JDK21 by Temurin.
That’s all well and good, but how do we install newer versions of the JDK when they roll off the assembly line?
One of these days, we’ll have regular JDK21 releases available straight from the package manager, but until that day comes, how are we supposed to update our installed version?

Well, I don’t have a silver bullet, but how about using Jenkins?
I’ve whipped up a nifty little Jenkinsfile that checks every day at 2:30 AM UTC if Temurin has pushed out a new nightly build for RISC-V.
If it strikes gold, it installs it into /home/jenkins/jdk-21.
It’s not exactly a masterpiece, since the version we’re using is in /opt/jdk21, but we could tweak it to shoot us an email when it finds something.
We’d then have to put Jenkins on ice, shuffle the contents of /home/jenkins/jdk-21 over to /opt/jdk21, and then wake Jenkins back up.

If you’re itching to give it a whirl, just whip up a new pipeline from source control and point it at the repo I mentioned earlier.
I’ll be the first to admit, even with an email notification, this workflow isn’t exactly a walk in the park, but it should be a stopgap solution, since Java 21 is set to launch on September 19, 2023.

Keep your ears to the ground for more updates and thrilling developments as we forge Jenkins' future together.

About the author

Bruno Verachten

Bruno Verachten

Bruno is a father of two, husband of one, geek in denial, beekeeper, permie and a Developer Relations for the Jenkins project. He’s been tinkering with continuous integration and continuous deployment since 2013, with various products/tools/platforms (Gitlab CI, Circle CI, Travis CI, Shippable, Github Actions, …​), mostly for mobile and embedded development.
He’s passionate about embedded platforms, the ARM&RISC-V ecosystems, and Edge Computing. His main goal is to add FOSS projects and platforms to the ARM&RISC-V architectures, so that they become as boring as X86_64.
He is also the creator of miniJen, the smallest multi-cpu architectures Jenkins instance known to mankind.