Very interesting. Reading this made me think of occam on the transputer: concurrent lightweight processes, message passing, dedicated memory! I spent some happy years in that world. Perhaps I should look at BEAM and see what work comes along?
I think the practitioner angle is what makes interesting. Too many BEAM advocacy posts are theoretical.
I would push back on the "shared state with locks vs isolated state with message passing" framing. Both approaches model concurrency as execution that needs coordination. Switching from locks to mailboxes changes the syntax of failure, not the structure. A mailbox is still a shared mutable queue between sender and receiver, and actors still deadlock through circular messages.
Stateless vs stateful concurrency management is very different, though; I can roll back / replay a mail box, while this isn’t possible with shared locks. It’s a much cleaner architecture in general if you want to scale out, but it has more overhead.
> Backpressure is built in. If a process receives messages faster than it can handle them, the mailbox grows. This is visible and monitorable. You can inspect any process’s mailbox length, set up alerts, and make architectural decisions about it. Contrast this with thread-based systems where overload manifests as increasing latency, deadlocks, or OOM crashes — symptoms that are harder to diagnose and attribute.
Sorry but this is wrong. This is no kind of backpressure as any experienced erlang developer will tell you: properly doing backpressure is a massive pain in erlang. By default your system is almost guaranteed to break in random places under pressure that you are surprised by.
Yes, this is missing the "pressure" part of "backpressure", where the recipient is able to signal to the producer that they should slow down or stop producing messages. Observability is useful, sure, but it's not the same as backpressure.
Occam (1982 ish) shared most of BEAMs ideas, but strongly enforced synchronous message passing on both channel output and input … so back pressure was just there in all code. The advantage was that most deadlock conditions were placed in the category of “if it can lock, then it will lock” which meant that debugging done at small scale would preemptively resolve issues before scaling up process / processor count.
Once you were familiar with occam you could see deadlocks in code very quickly. It was a productive way to build scaled concurrent systems. At the time we laughed at the idea of using C for the same task
I spreadsheeted out how many T424 die per Apple M2 (TSMC 3nm process) - that's 400,000 CPUs (about a 600x600 grid) at say 1GIPs each - so 400 PIPS per M2 die size. Thats for 32 bit integer math - Inmos also had a 16 bit datapath, but these days you would probably up the RAM per CPU (8k, 16k?) and stick with 32-bit datapath, but add 8-,16-bit FP support. Happy to help with any VC pitches!
And BEAM was the reimplementation of the Erlang runtime, the actual model is part of the language semantics which was pretty stable by the late 80s, just with a Prolog runtime way too slow for production use.
Very interesting. Reading this made me think of occam on the transputer: concurrent lightweight processes, message passing, dedicated memory! I spent some happy years in that world. Perhaps I should look at BEAM and see what work comes along?
I think the practitioner angle is what makes interesting. Too many BEAM advocacy posts are theoretical.
I would push back on the "shared state with locks vs isolated state with message passing" framing. Both approaches model concurrency as execution that needs coordination. Switching from locks to mailboxes changes the syntax of failure, not the structure. A mailbox is still a shared mutable queue between sender and receiver, and actors still deadlock through circular messages.
Stateless vs stateful concurrency management is very different, though; I can roll back / replay a mail box, while this isn’t possible with shared locks. It’s a much cleaner architecture in general if you want to scale out, but it has more overhead.
> Backpressure is built in. If a process receives messages faster than it can handle them, the mailbox grows. This is visible and monitorable. You can inspect any process’s mailbox length, set up alerts, and make architectural decisions about it. Contrast this with thread-based systems where overload manifests as increasing latency, deadlocks, or OOM crashes — symptoms that are harder to diagnose and attribute.
Sorry but this is wrong. This is no kind of backpressure as any experienced erlang developer will tell you: properly doing backpressure is a massive pain in erlang. By default your system is almost guaranteed to break in random places under pressure that you are surprised by.
Yes, this is missing the "pressure" part of "backpressure", where the recipient is able to signal to the producer that they should slow down or stop producing messages. Observability is useful, sure, but it's not the same as backpressure.
Occam (1982 ish) shared most of BEAMs ideas, but strongly enforced synchronous message passing on both channel output and input … so back pressure was just there in all code. The advantage was that most deadlock conditions were placed in the category of “if it can lock, then it will lock” which meant that debugging done at small scale would preemptively resolve issues before scaling up process / processor count.
Once you were familiar with occam you could see deadlocks in code very quickly. It was a productive way to build scaled concurrent systems. At the time we laughed at the idea of using C for the same task
I spreadsheeted out how many T424 die per Apple M2 (TSMC 3nm process) - that's 400,000 CPUs (about a 600x600 grid) at say 1GIPs each - so 400 PIPS per M2 die size. Thats for 32 bit integer math - Inmos also had a 16 bit datapath, but these days you would probably up the RAM per CPU (8k, 16k?) and stick with 32-bit datapath, but add 8-,16-bit FP support. Happy to help with any VC pitches!
Go is good enough.
The Node.js community had figured this out long before BEAM or even Elixir existed.
People tried to introduce threads to Node.js but there was push-back for the very reasons mentioned in this article and so we never got threads.
The JavaScript languages communities watch, nod, and go back to work.
> The Node.js community had figured this out long before BEAM or even Elixir existed.
Work on the BEAM started in the 1990s, over ten years before the first release of Node in 2009.
And BEAM was the reimplementation of the Erlang runtime, the actual model is part of the language semantics which was pretty stable by the late 80s, just with a Prolog runtime way too slow for production use.
You may be thinking of some recent round of publicity for BEAM, but BEAM is a bit older than JavaScript.
Such authority, much incorrect.
BEAM predates node js