Java 21 Virtual Threads - Dude, Where’s My Lock?

Netflix engineers encountered issues with virtual threads in Java 21 causing timeouts and hung instances in their microservices running on SpringBoot 3 and embedded Tomcat. Detailed diagnostics revealed that virtual threads were waiting for reentrant locks, with OS threads pinned and unable to release, leading to a variation of deadlock. The investigation and resolution process underscores the challenges and potential of adopting virtual threads for improved performance.