[23.1.0] Unable to find truffle-api/polyglott in embedded assembly

[ctabin]

Hi,

We are building a full assembly with GraalJS embedded in it. I created a simple project that easily reproduce the problem.

To summarize:

• when executed through maven with mvn -q exec:java, it works (meaning the dependencies are correctly declared).
• when executed through the command line on the full assemply with java -jar target/polyglott-full-embedded.jar, it crashes.

When launched with -Dpolyglotimpl.TraceClassPathIsolation=true, the output is:

[class-path-isolation] Start polyglot class-path isolation
[class-path-isolation] Collected 1 class-path entries from java.class.path system property
[class-path-isolation] Class-path entry: target/polyglott-full-embedded.jar
[class-path-isolation] No truffle-api and/or polyglot found on classpath. 
Exception in thread "main" java.lang.IllegalStateException: No language and polyglot implementation was found on the class-path. Make sure at last one language is added on the class-path. If you put a language on the class-path and you encounter this error then there could be a problem with isolated class loading. Use -Dpolyglotimpl.TraceClassPathIsolation=true to debug class loader islation problems. For best performance it is recommended to use polyglot from the module-path instead of the class-path.
        at org.graalvm.polyglot.Engine$PolyglotInvalid.noPolyglotImplementationFound(Engine.java:2071)
        at org.graalvm.polyglot.Engine$PolyglotInvalid.createHostAccess(Engine.java:2057)
        at org.graalvm.polyglot.Engine$PolyglotInvalid.createHostAccess(Engine.java:2023)
        at org.graalvm.polyglot.Engine$Builder.build(Engine.java:753)
        at ch.astorm.Main.main(Main.java:9)

One can see that truffle-api and/or polyglot is not found in the jar, but the classes are present in the assembly, hence there seems to be no reason to not to be found.

As a side note, this was perfectly working in 23.0.1 (by using the old maven artifacts).

Thanks & best regards.

[iamstolis]

This issue has nothing to do with graal-js. It is a failure of the initialization of Polyglot SDK.

One can see that truffle-api and/or polyglot is not found in the jar, but the classes are present in the assembly, hence there seems to be no reason to not to be found.

The failure is not about the classes themselves. It is about some module-related meta-data that your approach does not satisfy.

I will let @chumer to comment on whether this something that we support still and how.

[ctabin]

It seems I found a way to circumvent this problem in assembly:

java -Dpolyglotimpl.DisableClassPathIsolation=true -jar target/polyglott-full-embedded.jar

[thmarx]

This is an issue for me too.

[chumer]

I fear the Maven assembly plugin merges all dependencies into a single uber jar by default. Uber jars won't work with optimizations enabled since the optimizing runtime needs to run as a named module. The module information gets lost when creating the uber jar. The reason we need to run as a named module is that we need to access VM internals to perform optimizations and that is only possible when running as a named module. If you cannot use something else than an uber jar I fear the only option is to use -Dpolyglotimpl.DisableClassPathIsolation=true and run without optimizations enabled.

If you are using zip assemblies with a regular class path everything should work fine.
We generally recommend running using the module path for best performance if possible.

[chumer]

Maven Assemblies are now supported again with 23.1.2 and 24.0. I would still not recommend it, though.
See https://github.com/graalvm/polyglot-embedding-demo/blob/main/pom.xml#L315 for an example how to correctly configure it.