However, you can construct a reliable mechanism where one goroutine can start another and know whether or not the one it started has failed by using the available primitives, as I did in https://github.com/thejerf/suture . It's an easier problem since there's no cluster and no network that can get in the way. I've also done the exercise for the network case: https://pkg.go.dev/github.com/thejerf/reign#Address.OnCloseN... but that only functions within the network defined by that library because, again, it just isn't arbitrarily possible.
(I suppose it's relevant to some of my other comments to point out that I've also implemented basically Erlang-style concurrency in Go, with network, but as a relatively idiomatic translation rather than a blind one.)
Golang makes it easy to ignore errors that can be ignored and defer/recover provide a way to implement a way to “let it fail”
There’s even an implementation of supervisor trees for Go [0] :)
For instance, one thing I found when I was writing my library that will probably apply to most other languages (probably including Rust) is that Erlang has a somewhat complicated setup step for running a gen_server, with an explicit setup call, a separate execution call, several bits and pieces for 'officially' communicating with a gen_server, etc. But a lot of these things are for dealing with the exact ways that Erlang interacts with processes, and you probably don't need most of them. Simply asking for a process that makes the subprocess "start" from scratch is probably enough, and letting that process use existing communication mechanisms already in the language rather than trying to directly port the Erlang stuff. Similarly, I found no value in trying to provide direct ports of all the different types of gen_server, which aren't so much about the supervision trees (even if that's where they seem to be located) as a set of standard APIs for working with those various things. They're superfluous in a language that already has other solutions for those problems.
In addition to keeping an eye out for features you don't need from Erlang, keep an eye out for features in the host language that may be useful; e.g., the most recent suture integrates with the Go ecosystem's ever-increasing use of context.Contexts as a way to manage termination, which hasn't got a clear Erlang equivalent. (Linking to processes has some overlapping functionality but isn't exactly the same, both offering some additional functionality contexts don't have as well as missing some functionality contexts do have.)
Erlang has a lot of good ideas that I'd love to see ported into more languages. But a lot of attempts to do so flounder on these issues, creating libraries so foreign to the host language that they have zero chance of uptake.
The other thing I'd point out is that even in Go, to say nothing of Rust, crashing is actually fairly uncommon by Erlang standards. Many things that crash in Erlang are statically prevented at compile time in Go, and Rust statically precludes even more of them. However, I have found it OTP-esque supervision trees to be a very nice organizational structure to my code; I use suture in nearly every non-trivial Go program I write because it makes for a really nice modular approach for the question of "how do I start and stop persistent services?". I have seen it hold together runtime services that would otherwise be failing, the way it is supposed to, and that's nice, but the organization structure is still probably the larger benefit.
(There is deep reason for the way Erlang is doing it the way it does, which is that a lot of Erlang's type system, or lack thereof, is for communicating between nodes, so even if you perfectly program Erlang, if two nodes running different versions of code try to communicate with each other and they've changed the protocol you might get a pattern matching fail on the messages flowing between versions. The Erlang way of doing cross-machine communication with this sort of automatic serialization at the language level has not caught on, and all modern languages have a relatively distinct serialization step where this sort of error is better handled, as you try to deserialize the remote message into your internal data structure.)
Anyhow, the upshot is, you want to translate the functionality out of Erlang into other languages, not transliterate it.
> I can pretty much prove that they don't: https://github.com/thejerf/suture It's the process that needs monitoring, and that process may have 0-n ways to communicate. But that's not a criticism of Erlang, as I think that's actually what it does and it just happens to have a fused message box per process.
One, very neat library. Two, while I agree this proves the point that the actor model is not needed in the language to build a process supervisor, I think that your Go Supervisor looks a lot like an actor, at least in the way Erlang/Elixir uses them. From what I can see, the Supervisor itself works by looping over channel receives and acts on it. The behavior of the Supervisor lives in a separate goroutine, and you pass around an object that can send messages to this inner behavior loop via some held channels. So basically the object methods provide a client API and the inner goroutine plays the role of a server, in the same separate of responsibilities that gen_* uses.
If we squint a little bit, actors actually look a lot like regular objects with a couple of specific restrictions: all method calls are automatically synchronized at the call/return boundaries (in Go, this is handled explicitly by the channel boundaries instead), no shared memory is allowed, and data fields are always private. I'm sure this wouldn't pass a formal description, but this seems like a pragmatically useful form.
I agree that Go is less actor-oriented than Erlang/Elixir, but given how often I've seen that pattern you used in the Supervisor (and it's one I have also naturally used when writing Go) I'd argue that "Actor" is a major Go design pattern, even if it doesn't go by that name. The difference then, is the degree to how often one pulls out the design pattern. I think the FP aspect pushes Erlang/Elixir in that direction more, as this "Actor" pattern has a second function there -- providing mutable state -- that Go allows more freely.
This discussion has really made me think, thanks. I think you're right that actor-like features are valuable and that the Actor Model in the everything-is-an-actor is not itself the value (or even a positive).