[xcv123]

The difference now is that it's implemented in the JVM instead of a library / framework. It is easier, simpler, and probably more efficient. You can get higher throughput from existing code with minor refactoring.

  Thread thread = Thread.ofVirtual().start(() -> System.out.println("Hello"));
  thread.join();

[mikmoila]

Also there are some traceability issues involved in using asynchronous APIs: "In the asynchronous style, each stage of a request might execute on a different thread, and every thread runs stages belonging to different requests in an interleaved fashion. This has deep implications for understanding program behavior: Stack traces provide no usable context, debuggers cannot step through request-handling logic, and profilers cannot associate an operation's cost with its caller. "

https://openjdk.org/jeps/444

[saagarjha]

In theory an async-aware runtime can stitch together a coherent and useful backtrace, but in practice most legacy tooling won’t :(

[ElectricalUnion]

Collecting those potentially very expensive stack traces, specially in those highly concurrent environments with high throughput requirements would be great for debugging but probably is gonna kill the performance of the system. But it would be nice (even if as a very heavy hammer) as an option.

[Tainnor]

I'm not saying that virtual threads aren't a good thing (other runtimes than the JVM have had green threads for a very long time now), but that it doesn't seem like such a paradigm shift. It's still threads (with all the benefits and drawbacks), it's just now that they have less overhead.

Presumably I could just keep an existing server written in Spring MVC or a similar technology and just wait for the underlying container to support virtual threads to get the same benefits. I believe Jetty already does support them. So why would I need a new framework?

[xcv123]

It removes the need to write async code in many cases. It is a more straightforward and efficient way to accomplish what we have already been doing for years on the JVM.

You don't need to switch frameworks

https://spring.io/blog/2022/10/11/embracing-virtual-threads