Running `org.openhab.demo.app` with `org.openhab.automation.jsscripting` enabled

Nadahar · May 30, 2026, 1:33am

PRs created:

github.com/openhab/openhab-core

Disable Graal language cache (#5614)

main ← Nadahar:graalvm-cache

opened 12:29AM - 30 May 26 UTC

Nadahar

+5 -0

This change has been explained in greater detail [in a forum post](https://commu…nity.openhab.org/t/running-org-openhab-demo-app-with-org-openhab-automation-jsscripting-enabled/162466/21). The gist of it is that Graal has a static cache over installed languages that is frozen the first time it's retrieved. No changes after that point is registered, which is incompatible with OH's dynamic behavior of adding and removing add-ons, starting and stopping bundles etc. The fact that the cache is static also means that its lifetime is that of the JVM itself, nothing other than restarting the JVM will make it refresh. It also creates a race condition between Graal based add-ons where "the late one" might register too late to be cached, and thus "exist". Unfortunately, just disabling the cache isn't enough, because what can be retrieved when the cache is off seems "unstable", not thread-safe and classloader dependent. I've therefor made some alterations to the JS and Python add-ons that must be considered in combination with this PR. I also with for the combination to be tested. I use neither language myself, so I don't really know how to thoroughly test that there are no side effects from doing this. I will reference the add-ons PR when it has been created.

github.com/openhab/openhab-addons

Moidfy Graal engine creation to allow dynamic creation (#20810)

main ← Nadahar:graalvm-cache

opened 01:30AM - 30 May 26 UTC

Nadahar

+71 -50

This alters the classloader used during engine registration and `Language` retri…eval, and caches the `Language` instance. It must be seen together with https://github.com/openhab/openhab-core/pull/5614, and the goal is to allow dynamic registration of Graal engines. A description of both changes is given [here](https://community.openhab.org/t/running-org-openhab-demo-app-with-org-openhab-automation-jsscripting-enabled/162466/21), and this should allow installing and uninstalling Graal based add-ons without having to restart OH. It should also prevent the risk of one of them being unavailable if the timing of their creation during startup is unfortunate. It needs proper testing to make sure that creating these using the alternative classloader don't have other side effects, like failing to see resources that it previously could. I'm ill-equipped to do this testing, as I don't use any of these languages myself, and lack both "source rules" and the knowledge of how to properly test it.

I ask that somebody can find the time to test this. I can provide/build bundles to use for testing.