Custom ShutdownListener waiting for GracefulShutdownFilter used for gracefully shutting down HTTP requests?

[AndreasPetersen]

I'm looking at implementing at graceful shutdown handler for SmallRye Reactive Messages. I want to implement a PublisherDecorator that waits until all current messages have been acked or nacked, similarly to how the GracefulShutdownFilter works for HTTP requests.

I have a situation where an HTTP request emits a message to a channel. The request does not itself wait for the message to be acked or nacked. This means that I can get in a situation where:

• Shutdown initiated
• An http request is currently being processed, so the GracefulShutdownFilter waits to signal done
• My proposed PublisherDecorator shutdown listener checks if there are any outgoing messages. There are none, so it signals done.
• The http request now emits a message, and does not wait for ack/nack
• The http request now finishes, causing the GracefulShutdownFilter to signal done
• Quarkus shuts down
• Since my proposed shutdown listener has already signaled done, Quarkus did not wait for the emitted message to be acked/nacked

How can my proposed shutdown listener wait for the GracefulShutdownFilter to signal done, before checking for outgoing messages and signalling done itself? Is there another way to solve this issue?