Azure_function does not support returning a Mono from the controller when that Mono is created in a separate thread

[AaldertVanWijk-TomTom]

Expected Behavior

I would expect to be able to use the ability of Micronaut to return mono's from the Controller

Actual Behaviour

Returning a mono in the controller results in an empty response, when the creation of that mono is actually done on a separate thread.

    @Get("/mono")
    public Mono<String> mono(){
        return googleClient.healthMono().log();
    }

It's interesting, to see that there is no problem if we wrap the response in a flux:

    @Get("/flux")
    public Flux<String> flux() {
        return Flux.from(googleClient.healthMono()).log();
    }

Steps To Reproduce

As far as I can see returning a mono from an azure-http-function will fail when some of the work to create the mono is done on a separate thread.

I created a repository that shows the problem in it's shortest possible form.

https://github.com/AaldertVanWijk-TomTom/mono-with-azure-function/

The main branch shows the project with the netty runtime, and then all is working just fine. when I make a one letter change to the entire project change netty to jetty two tests start to fail. this is demonstrated on the jetty branch
The branch azure-function shows 3 tests failing when the project is an azure function. again with minimal changes

Environment Information

JDK 11

Example Application

https://github.com/AaldertVanWijk-TomTom/mono-with-azure-function/

Version

3.4.1

[alejojarahi]

I have the same problem, I am working on migrating from micronaut 2.5.13 an application based on azure function (Micronaut runtime azure_function) to micronaut > 3.0 and I have the same problem with reactor.