MP Fault Tolerance - default method fallback doesn't work in native mode

[pjgg]

Summary
I have a microprofile HttpClient on Native mode, and also a fallback action configured, then I got the following exception:

2021-01-18 10:36:17,661 ERROR [org.jbo.res.res.i18n] (executor-thread-1) RESTEASY002020: Unhandled asynchronous exception, sending back 500: java.lang.RuntimeException: Not implemented in native mode

Expected behavior
Same as JVM mode (if HTTP request fail, then move on to fallback)

Actual behavior

2021-01-18 10:36:17,661 ERROR [org.jbo.res.res.i18n] (executor-thread-1) RESTEASY002020: Unhandled asynchronous exception, sending back 500: java.lang.RuntimeException: Not implemented in native mode

To Reproduce

Setup an HttpClient pointing to a not found URL

@RegisterRestClient(baseUri = "http://microprofile-test:8080/")
public interface HelloClient {
    
    @GET
    @Path("/hello/notFound")
    @Produces(MediaType.TEXT_PLAIN)
    @Asynchronous
    @Fallback(fallbackMethod = "fallback")
    CompletionStage<String> getWithFallback();

    default CompletionStage<String> fallback() {
        return completedFuture("Fallback");
    }
}

And then make a query:

@Inject
@RestClient
HelloClient hello;

hello.getWithFallback().thenApply(result -> "Client got: " + result);

Jira ref

[mkouba]

CC @Ladicek

SmallRye has a workaround for default fallback methods: io.smallrye.faulttolerance.DefaultMethodFallbackProvider.getFallback(Method, ExecutionContextWithInvocationContext). However, this may not work in native mode and therefore the method is substituted in io.quarkus.smallrye.faulttolerance.runtime.graal.Target_io_smallrye_faulttolerance_DefaultMethodFallbackProvider.getFallback().

[Ladicek]

Yea I've noticed that, and chose to forget about it because supporting it will probably require non-trivial changes in SRye FT :-) Assigning to myself, but it will take a bit of time.

[geoand]

I think in GraalVM 21 support method handles better now so maybe this can be re-examined?

[rsvoboda]

@Ladicek can you look into this regression again? Quarkus is on GraalVM 21 now.

[Ladicek]

I'll try (remove the substitution and verify), but no promises if it doesn't work out :-)

[Ladicek]

Confirm that with GraalVM 21 and the substitution removed, it works. I'll take a look where to add a test and submit a PR.

[Ladicek]

Submitted #15788.

[Ladicek]

Also, let's make one thing clear: this is not a regression. This has never worked :-)