Show HN: Visual flow-based programming for Erlang, inspired by Node-RED

Re:Show HN: Visual flow-based programming for Erlang, inspir... by neonsunset on Friday May 16, 2025 @04:42PM (#44009646)

Usually dual APIs are offered when they do distinctly different things. Async calls on Socket go through epoll/kqueue via SocketAsyncEngine, which has observably different behavior to regular sockets. There is no such duality in high-level APIs like HttpClient's `.GetStringAsync`.

You are not free from having to worry about it with virtual threads either. If you block a carrier thread with such a low-level API call, the runtime will have a bad time. Or you will always end up paying for a context switch (if you maintain a separate pool of block-able threads).

Green threading UX is better for "regular" code that never bothers to take advantage of concurrency features, but if you do want them, you are quickly back to usually more ceremonious structured concurrency abstractions which, lo and behold, can reimplement the same task system with a worker pool but on top of virtual threads.

If you start to care about cancellation, suddenly you are back to coloring problem regardless. I agree with you that having to write many await's in quick succession is tiresome and unnecessary. It's partially a fault of library authors who name methods "GetSomeLongNameAsync" instead of "Get" or "Query". But other than this it's not as invasive as people make it out to be, and encourages writing highly concurrent code - reducing latency 2x can require moving one or two awaits around. Not so much in Java/Erlang/Go.

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Re:Show HN: Visual flow-based programming for Erlang, inspir... by SigmundA on Friday May 16, 2025 @04:58PM (#44009776)

I haven't found this is the case many times, many api will have two versions of the api with XxxAsync versions all the way down, maybe less so now days but it took a while to get async entry points added everywhere so you could use it properly, such as ActionResult.ExecuteResultAsync and IAsyncEnumerable as a couple examples.

HttpClient one prime example and you can see the back and forth here internally from MS: https://github.com/dotnet/runtime/issues/32125

This snippet of code or something like it has been used in countless libraries to try and give a workable sync over async which should be baked in: https://github.com/aspnet/AspNetIdentity/blob/main/src/Micro...

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Re:Show HN: Visual flow-based programming for Erlang, inspir... by neonsunset on Friday May 16, 2025 @05:01PM (#44009801)

I suppose the difference of opinion comes down to whether you consider hiding side effects a good or a bad thing. And whether you want to have easy composition and cancellation (Go struggles with passing context around a lot, in .NET it's much less of an issue if at all, depending on codebase).

If you don't want to join on some other virtual thread or goroutine completing immediately (and with Goroutines it's additionally painful since you need to communicate completion separately), it's more difficult and costlier than doing so with tasks/futures.

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Re:Show HN: Visual flow-based programming for Erlang, inspir... by SigmundA on Friday May 16, 2025 @05:14PM (#44009870)

CancellationTokens can be passed in synchronous functions just fine, I have done cancellable sync apis before cancellation tokens existed usually its a .Cancel() on the thing doing the work just like Command.Cancel() in the Sql client or Connection.Cancel() in a network client. I agree CancellationTokens are better and always use them now and thats not the problem with async.

The problem is the need to color functions with async and if you have existing client code that call existing synchronous methods it not easy to move their internal implementations to async form so that you can remain backward compatible without copy/pasting the same layers of code with different function coloring to async.

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