Log4j2 not working with Spring Boot 3.4.2 together with BlockHound

[micopiira]

When upgrading to Spring Boot 3.4.2 our logging stopped completely working.

After narrowing down I figured the problem happens with Spring Boot 3.4.2 when using Log4j2 together with BlockHound.

Here is a minimum reproducer repo: https://github.com/micopiira/spring-boot-log4j2-issue

Spring Boot 3.4.1 with exact same Log4j2 version and BlockHound version works.

Spring Boot 3.4.1:

Spring Boot 3.4.2:

[wilkinsona]

Thanks for the report and for the minimal sample. I assume that something has changed in Spring Boot 3.4.2 that is causing BlockHound to break Log4j2 in some way. Unfortunately, given that this works fine without BlockHound and the way in which BlockHound works, I don't think there's anything we can do about this in Spring Boot. Please raise a BlockHound issue so that they can investigate further.