Quarkus from 3.11 cannot load RestClient generated classes in Kotlin CoroutineScope about quarkus

[mschorsch]

I dont understand why you wrap the Rest Client call into withContext? Quarkus REST Client supports suspend functions so you can simply mark your REST endpoints suspendable. Another option is to use https://smallrye.io/smallrye-mutiny/latest/guides/kotlin/ and use awaitSuspending on the returned Uni.

[DarthRevanXX]

@mschorsch got it, makes sense, thanks

[quarkus-bot]

/cc @geoand (kotlin)

[DarthRevanXX]

@mschorsch due by using withContext(Dispatchers.IO) ensuring that such operations run on a thread pool optimized for I/O, preventing the main thread or other critical threads from being blocked. For example database calls, network calls

[mschorsch]

@DarthRevanXX The idea of reactive programming (Mutiny, Vert.x Futures/Promises, CompletionFuture, Kotlin Coroutines, ...) is simplified by being able to process many requests with just a few threads (Vert.x IO threads). Using a separate thread pool works against this idea and is not necessary and counterproductive in the case of the REST client.

[Sic4Parvis9Magna]

@mschorsch , sorry for leaving this ticket w/o attention for a few weeks.
So let's cross-check what we've got here to conclude the discussion and close the ticket.

1. Even if the issue appears to be related to Quarkus changing class loaders in and out of the coroutine's scope with migration to 3.9 it is not what we are about to "fix" here as it works as intended.
2. What we need to fix is how we use Quarkus rest clients with suspension functions.
   To do so we need to move from:

    suspend fun getExtensions(id: String?) : List<Extension> {
        return withContext(Dispatchers.IO) {
            extensionsService.getByIdAsUni(id)
        }.awaitSuspending().toList()
    }

To this:

    suspend fun getExtensions(id: String?): List<Extension> {
        return extensionsService.getByIdAsUni(id)
            .awaitSuspending().toList()
    }

Please confirm if I got everything right 🙏

[mschorsch]

@Sic4Parvis9Magna

I have tested your reproducer but could not reproduce the error you reported. Everything worked as desired without explicitly setting the classloader.

Even if the issue appears to be related to Quarkus changing class loaders in and out of the coroutine's scope with migration to 3.9 it is not what we are about to "fix" here as it works as intended.

I'm not part of the Quarkus team so I can't speak for the Quarkus team but I guess so. @geoand ist that right?

What we need to fix is how we use Quarkus rest clients with suspension functions.

Yes, that is more efficient. Another option is to mark the methods directly as suspendable in the rest client.

@Path("/extensions")
@Named("ExtensionsService")
@RegisterRestClient(configKey = "extensions-api")
interface ExtensionsService {
    @GET
    suspend fun getById(@RestQuery id: String?): Set<Extension>
}

// ...

@ApplicationScoped
class CoService(
    @Named("ExtensionsService")
    @RestClient 
    private val extensionsService: ExtensionsService
) {

   suspend fun getExtensions(id: String?): List<Extension> {
        return extensionsService.getById(id).toList()
    }
}

[geoand]

I'm not part of the Quarkus team so I can't speak for the Quarkus team but I guess so. @geoand ist that right?

Seems correct to me

[geoand]

Yes, that is more efficient. Another option is to mark the methods directly as suspendable in the rest client.

+1