[amluto]

Threads (whether lightweight or heavyweight) can’t fully replace reactive/proactive/async programming even ignoring performance and scalability. Sometimes network code simply needs to wait for more than one event as a matter of functionality. For example, a program might need to handle the availability of outgoing buffer space and also handle the availability of incoming data. And it might also need to handle completion of a database query or incoming data on a separate connection. Sure, using extra threads might do it, but it’s awkward.

[pron]

> Sure, using extra threads might do it, but it’s awkward.

It's simpler and nicer, actually — and definitely offers better tooling and observability — especially with structured concurrency: https://download.java.net/java/early_access/loom/docs/api/jd...

[jonpez2]

Let me preface by saying I am a Johnny-come-lately loom fanboy. Amazing work and huge impact. Re structured concurrency: I wonder if there’s any way to combine with generic exceptions such that we can not force a wrapping exception class. So maybe have an executor class that’s generic on the thrown exception type, and then have the join or get apis explicitly throw that type? This thought process is inspired by the goto-considered-harmful trail of logic: I think it would get us even closer to concurrency encapsulated in function blocks.

[pron]

Convenient polymorphism over exceptions is something I would very much like to see in Java, but it's a separate topic. Given that structured concurrency is normally used with things that can fail, and whose failures must be handled, I hope (and think) you'll find that the use of checked exceptions is not onerous at all. If we're mistaken, we can consider solutions during the incubation period.

[jonpez2]

Totally agree that we need explicit handling of the concurrency-specific exceptions like interruptedexception. It’s just that concurrent apis by their nature take callable/runnable apis which lose any formality over exceptions thrown by client code, and thus someone up the stack is always forced to write a catch( Throwable ) block. So the concurrency leaks up the stack, and forces unsafe default clauses. You’re clearly correct that the topic is separate, but it has great impact on the leakiness of these apis.

Thanks for the response and the amazing work!