ClassCastException during verticles deployment with Vert.x 4

[tho...@melusyn.com]

Hi, 

We are currently upgrading our microservices from Vert.x 3.9.x to 4.x and face issues during the deployment.

We have a main verticle responsible for the deployment of the others. It uses a Maven Service Factory: https://vertx.io/docs/vertx-maven-service-factory/java/ 

Since the upgrade to vert.x 4, a ClassCastException is thrown when deploying at least 2 different verticles. This exception occurs when facing any external dependency. 

I have made a reproducer for vert.x 4, here: https://github.com/thomas-melusyn/vertx-examples forking the vertx-examples from the official repo.
Strangely, I was not able to make the tests succeed with vert.x 3.9 (see branch vertx-3.9).

When running the unit test,  this error is thrown: 
java.lang.UnsupportedOperationException
at io.vertx.core.impl.VerticleManager.lambda$deployVerticle$2(VerticleManager.java:166)
at io.vertx.core.impl.future.FutureImpl$3.onFailure(FutureImpl.java:128)

With the help of the debug, we can find the underlying exception: 
java.lang.ClassCastException: io.vertx.ext.mongo.impl.MongoClientImpl$MongoHolder cannot be cast to io.vertx.ext.mongo.impl.MongoClientImpl$MongoHolder
Here's the debug console:

I've tried a lot of things to understand where this could come from but I haven't found a clue yet. 

Does anyone have faced a similar error? 

How do you deploy multiple verticles at the same time with a parent verticle deploying other ones?

Best 
Thomas

[Thomas SEGISMONT]

Hi,

This ClassClastException happens because the MongoHolder class has been loaded in two different IsolatedClassLoader instances.

Vert.x should not load its classes in IsolatedClassLoader. Can you please file an issue to Vert.x core? Thank you

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[Julien Viet]

with a reproducer :-)

To view this discussion on the web, visit https://groups.google.com/d/msgid/vertx/CACiEr_SLryaRr6JgzBewOnqCs30-Fu%3DJeYVWaykbj9A%2BVbsQHQ%40mail.gmail.com.

[tho...@melusyn.com]

Thank you, 

here's the issue I just created https://github.com/eclipse-vertx/vert.x/issues/3987
I included the link of the GitHub repo with the reproducer