Spring Exception when trying to use HTTP/2 with two different Spring versions

Affects: 2.3.12.RELEASE

I'm sending the data from one service (the client) to another (the server) using HTTP/2. Both services use reactive stack. When both services use version 2.7.1 of Spring Boot (reactor-netty version 1.0.20), everything works fine. But when I downgrade the client to the version 2.3.12.RELEASE (reactor-netty version 0.9.20.RELEASE) the code stops working, and exception is thrown:

reactor.core.Exceptions$ErrorCallbackNotImplemented: java.lang.UnsupportedOperationException: unsupported message type: DefaultFullHttpRequest (expected: ByteBuf, FileRegion)
Caused by: java.lang.UnsupportedOperationException: unsupported message type: DefaultFullHttpRequest (expected: ByteBuf, FileRegion)

I created a minimal reproducible example to demonstrate the issue. It's a multi-module Gradle project. One module represents the server, and another module represents the client. The main branch contains working example (both services with version 2.7.1), and the minimal-reproducible-example branch illustrates the problem.

Unfortunately, in the real project, the client service uses 2.3.12.RELEASE version, and upgrade to the newest one is not that easy. Is there any way to make it work without the Spring Boot upgrade?

Comment From: karolkrasnowski

I don't want this to sound rude, but when can I expect someone to take care of this issue?

Comment From: bclozel

Spring Boot 2.3.x is out of OSS support - can you reproduce this with a supported version?

See https://spring.io/projects/spring-boot#support

Comment From: karolkrasnowski

Thanks for your reply. This problem does not occur in version 2.6.0 so I suppose that this issue can be closed.