Yeah, similarly, Joe Armstrong (RIP), co-creator of Erlang explained it to me like this:
> In distributed systems there is no real shared state (imagine one machine in the USA another in Sweden) where is the shared state? In the middle of the Atlantic? — shared state breaks laws of physics. State changes are propagated at the speed of light — we always know how things were at a remote site not how they are now. What we know is what they last told us. If you make a software abstraction that ignores this fact you’ll be in trouble.
He wrote this to me in 2014, and it has really informed how I think about these things.
The thing is that go channels themselves are shared state (if the owner closes the channel and a client tries to write you're not gonna have a good time)! Erlang message boxes are not.
Strictly speaking they’re shared state, but the way you model your application around channels is generally to have independent little chunks of work and the channels are just a means of communicating. I know it’s not one-for-one with Erlang.
You can think of closing the channel as sending a message “there will be no further messages”, the panic on write is enforcement of that contract.
Additionally the safe way to use closing of a channel is the writer closing it.
If you have multiple writers, you have to either synchronise them, or don’t close the channel.
Sure but the fact that it is shared state is why you can't naively have a go channel that spans a cluster but Erlang's "actor" system works just fine over a network and the safety systems (nodedowns, monitors etc) are a simple layer on top.
You don't have to close a channel in Go and in many cases you actually shouldn't.
Even if you choose to close a channel because it's useful to you, it's not necessarily shared state. In a lot of cases, closing a channel behaves just like a message in its queue.
Maybe. Or maybe we observe the same point of information source from two points which happen to be distant in the 3-coordinates we are accustomized to deal with, but both close to this single point in some other.
> In distributed systems there is no real shared state (imagine one machine in the USA another in Sweden) where is the shared state? In the middle of the Atlantic? — shared state breaks laws of physics. State changes are propagated at the speed of light — we always know how things were at a remote site not how they are now. What we know is what they last told us. If you make a software abstraction that ignores this fact you’ll be in trouble.
He wrote this to me in 2014, and it has really informed how I think about these things.