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ARTEMIS-5948 Use Varhandle implementations from jctools#6289

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cortlepp wants to merge 2 commits intoapache:mainfrom
cortlepp:safe-jctools-queues
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ARTEMIS-5948 Use Varhandle implementations from jctools#6289
cortlepp wants to merge 2 commits intoapache:mainfrom
cortlepp:safe-jctools-queues

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@cortlepp
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@cortlepp cortlepp commented Mar 11, 2026

Artemis currently uses some queues from jctools-core which rely on sun.misc.Unsafe internally. These methods are deprecated in JDK24+, issue a warning at runtime and will be removed in future versions of the JDK. Thus it makes sense to switch to an implementation which does not rely on those methods.

In their latest release JCTools have started to publish a new artifact, jctools-core-jdk11, which contains alternative Varhandle based implementations which do not use Unsafe. As far as I understand them they are designed to be a drop-in replacement to the existing Unsafe implementations.

@clebertsuconic
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If we could wait the 2.53.0 release.. only merge this after 2.53 please?

@cortlepp
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Currently org.apache.activemq.artemis.tests.integration.karaf.ArtemisFeatureTest is failing in JDK 17 and 21 (it passes in JDK 25) on line 152. I can't really tell from the test what the underlying problem is, since the test works with a timeout it might also just be flakiness. If someone knows more about this I would appreciate any advice.

@gemmellr
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If we could wait the 2.53.0 release.. only merge this after 2.53 please?

I'd agree that would make sense. Its not yet mergeable anyhow though.

@gemmellr
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Currently org.apache.activemq.artemis.tests.integration.karaf.ArtemisFeatureTest is failing in JDK 17 and 21 (it passes in JDK 25) on line 152. I can't really tell from the test what the underlying problem is, since the test works with a timeout it might also just be flakiness. If someone knows more about this I would appreciate any advice.

Note that the JDK25 fast-tests job passed only because the failing test is not run on JDK25. At least at the time Artemis started working on 25, Karaf didnt work on 25, so those tests had to be omitted.

I believe it failing on the line it is indicates the server bundle failed to start. I seem to recall there being a dir somewhere deep in the target dir where you can find the logs to help diagnose further.

@gemmellr gemmellr marked this pull request as draft March 11, 2026 14:24
@cortlepp
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@gemmellr thanks for the advice, I had not noticed that the test isn't executed on JDK25 and I also found the logs you are referring to. Unfortunately though, they didn't tell me much.

The startup fails because the server does not find org.jctools.queues.MessagePassingQueue, even though before that it printed the jctools-core (and jctools-core-jdk11) coordinates before (which I interpreted as it loading these classes). I then thought that maybe the transitive dependency on jctools-core via jctools-core-jdk11 could not be resolved here, so I added explicit dependencies on jctools-core wherever jctools-core-jdk11 was used, but that didn't seem to change anything.

I'm a bit out of my depth here and don't know what I could investigate further. Maybe you can take a look at the logs, see if anything seems off? I attached two logs to this comment, one before my changes and one after, both captured when running on JDK 17.0.16 (Temurin).

pass.log
fail.log

@gemmellr
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gemmellr commented Mar 17, 2026

From the logs the original jctools-core and new jctools-core-jdk11 modules do both seem to be getting loaded, but its failing to load an class/interface thats from the original jctools-core module, something it can only be attempting if either there is a direct usage of that still in the codebase, or if the classes used from jctools-core-jdk11 are doing it indirectly. The latter seems to be the case here, and likely gives the source of the problem.

Looking at the jctools-core-jdk11 jar OSGi metadata in META-INF/MANIFEST.MF file, it does not import/say-it-uses any packages from jctools-core at all, so I expect as a result it then cant actually load the classes/interfaces that it depends upon. Essentially I'd guess you could remove artemis-server-osgi from the equation and the same would still happen as jctools-core-jdk11 is likely just broken for OSGi.

@cortlepp
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@gemmellr thank you so much, that seems to have been the problem. I added the dependency in JCTools and the test now works on my machine. I already created an Issue & PR in JCTools (JCTools/JCTools#411, JCTools/JCTools#412), hopefully we can get this resolved quickly :).

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3 participants