Missing ByteBuf.release() in GraphQL

[umarti]

My web app logs an exception in Spring Boot 3.5.5, using Kotlin, WebFlux, and extensive use of GraphQL subscriptions.

stacktrace.txt

Run configuration:
-Dkotlinx.coroutines.debug=on -Dkotlinx.coroutines.stacktrace.recovery=true -Dio.netty.leakDetection.level=PARANOID

Problem
The exception occurs once on every Spring Boot startup, right after the first web requests.
I’d like to track this down because I’m worried about potential side effects (e.g. memory leaks).

Question
Does anyone with experience in this area have advice on how and where to debug this issue?

[bclozel]

This seems linked to websocket requests? I cannot reproduce this right now.

I have tried to reproduce this with Spring Boot 3.5.5, WebFlux and a websocket subscription streaming data for some minutes but couldn't see anything in the logs. Could you work on a minimal sample that reproduces the problem? Thanks!