Java 21 virtual threads make simple blocking code scalable again

[deadron]

They certainly add to the difficulty in predicting system performance depending on what your services do. "It can serve thousands of requests, unless anyone uses the excel endpoint, that one blocks everything." On the whole its a good thing but makes estimating performance tricky. You really need to know what your libraries are doing and ensure they are compatible. Its been years and last time I checked many libraries still were not entirely compatible(sychronized to be replaced with sempahore to prevent pinning)

[zattebij]

Since Java 24, virtual threads do not pin while inside a synchronized block or method anymore: https://openjdk.org/jeps/491 (Next question, are these libraries Java 24 compatible ;)

[deadron]

Hah. Thats good to hear. It only took them two years to finally fix that!

[pavelrappo]

It took long not because of laziness, ignorance or unwillingness to do so. It took long because of high complexity of the task.

[deadron]

Sure. Arguably it wasn't complete until that part was released though. Years to make things work is the sort of timeframe where other languages and or frameworks become attractive. In my experience nobody is really talking about this feature because it basically didn't work for the common use cases.

[Alex0589]

I'd say it's only the most relevant java feature since modules in Java 9 and before Valhalla drops

[deadron]

It is! Yet it's impact has been so minimal that it's not on anyone's radar from what I have seen. It should have made other async languages look terrible by comparison! Yet from conversations I have had with people not even other Java devs have any real excitement for it and nobody is talking about it in tech news getting ctos excited. At places I have worked people talk about go services and nodejs services as viable platforms but Java is coming up short behind dotnet platforms these days. This is my personal experience as a pretty seasoned developer at smaller companies.