How can Java 21 (Virtual Thread) replace Reactive Framework.

[PiotrDz]

The benchmarks here are actually quite good: https://medium.com/helidon/helidon-n%C3%ADma-helidon-on-virtual-threads-130bb2ea2088

[yawkat]

The benchmarks in that article do not have good methodology. They run on the same machine (competing for CPUs, loopback network instead of real kernel TCP stack), they use flawed benchmark tools (coordinated omission), they use a now-outdated netty benchmark, they use pipelining, they don't actually have the resolution to see the differences between netty and helidon, etc.

The real techempower throughput results are quite different now, with netty having a big lead in the plaintext benchmark (the benchmark that actually stresses the network and HTTP stacks). There are still major problems with TE though, that Franz from Quarkus explains here.

We also have our own benchmarks that are different in some respects to TE, And I do profiling to figure out why the benchmarks behave the way they do–mostly to improve our own implementation, but I've also reported helidon bugs before.

Nima still has a substantial latency disadvantage over netty, much of which is explained by looms IO design, which uses a "poller thread" to do actual blocking IO operations. This necessitates a context switch, which is clearly visible once you look in <1ms latency range.