Lunatic is an Erlang-inspired runtime for WebAssembly
lunatic.solutions
lunatic.solutions
If they happen to load all dependencies into a giant blob of linear memory, C written extensions will take care of corrupting their runtime's memory, regardless of WebAssembly "security".
(Sure, you could screw it up if the caller accepts a negative-size bitmap and corrupts its heap. Lets assume that process is written in a memory-safe language.)
If Lunatic can do that, it would be a game changer for distributed computing.
For example, Kay https://github.com/aeplay/kay (used in https://aeplay.org/citybound)
I'm less sure about Axiom https://docs.rs/axiom/0.2.1/axiom/
And then there is Bastion https://crates.io/crates/bastion that I think allows moving an actor to another machine
I think I saw some Rust library do this but I can't find it.
We are working on a distributed lunatic implementation built on top of nats.io.
Like Flash, Silverlight and Java, it allows the embedding and running of binary applications in the browser (although currently this also requires a Javascript shim to allow access to the DOM.) Unlike those, however, Webassembly is not intended to be used only by a single language. You can compile C, C++, Rust, and many other languages to Webassembly and run them both in the browser and as native applications.
This stacks with DOM sandboxed APIs so you get same level of isolation in the browser as JS but better perf and a memory model more suitable to other languages.
Outside of browser you still get sandboxed low level VM suitable for running C and other low level languages. Eg. you could compile a C module for say node and ship it compiled as WASM
That's a high bar. It needs to be portable to everywhere web browsers run, and it needs to be sandboxed so that it's safe to run downloaded code.
WebAssembly is now widely used outside of web browsers as well. The article linked here is not about web browsers; Lunatic runs on a server.
I think the best way to think of it is that "WebAssembly" is a great marketing name, but what it does is be a modern-day JVM: a byte code language that can run anywhere.
You have also removed the shackles of JS and provided an environment to which you can compile and you get the ability to port a lot of libraries and code to the new platform. How does this help? One, you can use other languages to write apps for the web. Two, you can use existing libraries to help develop your app. Three, by having a permission system to access system resources in a secure way, you can incorporate native application features and performance into your web app. Think about stuff like direct printer access, USB access, etc.
As someone who doesn't mind the "shackles" of JS, from what I have seen so far, apps written in WebAssembly are up to two times slower than their JS counterparts. DOM access is abysmal, and from what I've seen in the wild, no one has written a serious business critical application using it yet.
What does webassembly do today, and what experience does it provide over javascript? I get the sandbox and distribution, but again, those advantages mostly apply to JS as well.
There are lots of such applications, including:
* Figma
* Unity games on the Web
* Google Earth
* AutoCAD
* Aside from entire applications, crucial features in things like Zoom and Google Meet (filters, backgrounds, etc.).
WebAssembly won't replace JavaScript - it's for different things. Wasm lets you port native code to the Web, and it lets that type of code run very fast. That's even without SIMD and multithreading - with those things, wasm is even faster.
I'm not even a JS dev but it is certainly literally mind-blowing once you see it.
How does messaging work between processes? What sort of overhead is involved?
Processes don't share any memory, so the message will need to be copied from one process to another. This should be the biggest overhead involved when sending them.
Erlang uses a trick for big binary data structures, they are allocated inside a common memory space and reference counted. That way big messages can be sent just by reference. I was thinking of doing something similar, the wasm spec allows you to import multiple memories and one of the memories could be a commonly shared one. The only issue is that most higher level languages, like Rust, don't have a concept of multiple memories. So it would be really hard to use this trick inside them.
Once we can run lunatic in a distributed way, some messages will need to be sent over the network and we can't cheat there. From this perspective it's even better if we can force architectures where the messages stay small.
> All processes running on Lunatic are preemptively scheduled and executed by a work stealing async executor.
Sounds like Erlang to me.
Erlang is special for other reasons.
Some things that would make it more like Erlang than Go (but that I won't bother to verify):
1. Go isn't really pre-emptive, it just has a lot of hidden yield points afaik
2. Go doesn't enforce message passing, Erlang obviously does
3. When you send a message to a goroutine that has panicked you hang and, potentially at some point, panic. In Erlang an actor dying can send out a final exit message that other actors (likely a supervisor) can subscribe to.
So yeah IDK. To me if it's got lightweight processes, pre-emption, and message passing, it's got everything that makes Erlang special. If it says it's inspired by Erlang I'm going to assume that, along with those things, it also shares goals like fault tolerance.
Actors do not an Erlang make. What makes an Erlang:
- Isolation. A crash in an actor cannot bring down other actors. Cannot bring down the runtime
In Go `panic` crashes the program. In Erlang "panic" crashes an actor, and... that's it.
- Monitoring. The above makes an important property of the system: a process can be monitored, and when it dies you can be guaranteed to receive a message that it died, and why
This lets you build things like supervision trees that are impossible/hard/ineffecient(chose two) in other languages.
- Everything in the VM is aware of processes, concurrency and parallelism
Every process gets its fair share of time: each process gets X "reductions". A reduction is a function call, or a message pass. Each function call or message pass reduces the counter. Once it reaches zero, the process is put on hold, and the next process is run.
This means that almost everything in the system, including the VM itself is re-entrant. Even Erlang's regexp implementation is re-entrant. You never even have to think about "wait, if I call this function, and the process is put on hold, what happens". The process will be re-awakened and continued.
----
The first two are what makes Erlang special. The rest is gravy, and there is quite a lot of it on top.
Erlang doesn't enforce message passing. You can use ets tables to coordinate processes (but don't).
A lot of pls claim erlang inspiration, e.g. pony, but miss some very important points and focus on "actors". Erlang isn't even really an actor system at heart, it just looks like it superficially. Actor systems at their core are message and coordination focused; when you write an erlang or elixir program you are typically minimizing the message passing because it is imperformant and hard to reason about. The raison d'etre of erlang processes is not really message passing concurrency, it's failure domain definition and failure domain bundling (if x crashes also crash y, because now the state of y can't be trusted).
At some level this is true of all systems - you can't yield in the middle of a `mov`, for example. But as Erlang is interpreted it doesn't rely on yield points. The caveat is that it does if you use CFFI.
> You can use ets tables to coordinate processes (but don't).
Yeah I'm sure there are endless ways to bypass the intended use of Erlang, I don't think it's really important. This is way different from Go where data is trivially shared across a channel.
> The raison d'etre of erlang processes is not really message passing concurrency, it's failure domain definition and failure domain bundling
Yes, this is true. The foundation of Erlang is based on earlier research that Armstrong cites in his thesis paper, such as the persistent process and transaction as the basis of system resiliency. But it's not a coincidence he landed on actors to express those things.
> The caveat is that it does if you use CFFI.
No shit, I wrote a huge FFI library for the BEAM (that even implements a yielding system.that interops with erlang's yields), that's a huge part of my point about the beam not really being preemptive.
> But it's not a coincidence he landed on actors to express those things.
Yes, that's my point. In erlang the conceptual arrow goes (resiliency => not-really-but-kinda-like-actors). In these other systems, or at least the ones I've peeked at, like pony and bastion the logic goes (actors => underpants gnomes => something like erlang). It's completely backwards.
This is basically what I'm saying... at some point nothing is preemptive ie: at the instruction level.
> that's a huge part of my point about the beam not really being preemptive.
OK but I think that's really semantics, it doesn't really matter though. You are right that BEAM can't yield within an instruction or during FFI. If you think that means it isn't preemptive, ok, but as I said I think at some point you end up with "nothing is preemptive" and then "why do we have the word preemptive" and then "because it's useful to describe systems like BEAM".
> Yes, that's my point. In erlang the conceptual arrow goes (resiliency => not-really-but-kinda-like-actors). In these other systems, or at least the ones I've peeked at, like pony and bastion the logic goes (actors => underpants gnomes => something like erlang). It's completely backwards.
Sure, actors aren't "the point". They just satisfy important properties that are necessary for resiliency. Pony takes a very very different approach from Erlang. Bastion seems closer.
I don't think "distance from Erlang" is really important or interesting though. Inspiration from Erlang is present in many of these systems, whether they re-implement the exact concepts or not.