Comment by haberman | Hacker News Reader

Comment by haberman | Hacker News Reader

I'm trying to figure out what Extism is actually providing here.

The underlying runtime appears to be Wasmtime, an existing project that you can use separately.

For the system API, Extism supports WASI (a POSIX-like API for WASM) which is already supported by Wasmtime. However it sounds like it also has a different, non-WASI API that provides similar functionality. I'm curious to hear a compare/contrast between these two system APIs, or what motivated inventing a new non-WASI system API. It does appear that WASI is in its early days; WASI was announced in 2019 (https://hacks.mozilla.org/2019/03/standardizing-wasi-a-webas...) but it appears that all of the specific proposals are still early stage and far from being standardized (https://github.com/WebAssembly/WASI/blob/main/Proposals.md).

For the API, Extism provides a C API/ABI that can be called through FFI, but AIUI Wasmtime already has such an API: https://docs.wasmtime.dev/c-api/

Basically I'm trying to understand the conceptual difference between this project and Wasmtime.

It's a good question. It's hard to understand what all is involved in building something like that until you have to get into the details. You can think of Extism as a layer around wasmtime. There is an ABI of sorts that helps you communicate with the plugin: Send data to it, invoke functions, and get data out. With our system, you don't need to enable WASI to use a plugin. You can invoke functions directly. However, you can use WASI for other purposes. And we are working on a way to do POSIX-like stuff (e.g. programs with a main function that use stdin and stdout).

Because we wrap wasmtime, we can also switch it out. That's how we are able to run the same plugins in the browser. There we use the browsers' implementation.

I think one day we will replace some internal pieces of Extism with pieces of the Component Model spec. As of today it's not in a state where we can do all of this in this many languages.

edit: rewording, grammar

Hey! Super exciting to see your progress on Extism.

I'm Syrus, from Wasmer. I did a quick review of your plugin architecture and it looks great (tons of languages supported, congrats!). I think Wasmer might be able able to help you so you have the same implementation of the runtime inside and outside of the browser (something similar as we did in wasmer-js [1], where we reuse same WASI implementation, but using the native Wasm engine from the browser).

I'd love to see how we can integrate your plugins into Wasmer as well!

[1] https://github.com/wasmerio/wasmer-js

Syrus, thanks for the kind words! Would love to work with you on integration. I'll reach out & find some time to sync up on it. Or, feel free to join our Discord and we can loop in the team: https://discord.gg/cx3usBCWnc

Thanks Syrus! wasmer-js looks really cool.

Linking wasmtime with host functions through the c abi is a bit cumbersome so I believe (in theory) this product can serve a real need by making plug-in integration more streamlined. Wasm as new plugin target / intermediary is a nobrainer (unless your game is written in c# or you like lua)

That makes sense, thanks. It sounds like a key difference is that Extism is trying to be portable to both web and standalone WASM runtimes. And maybe part of the motivation for a new WASI-like API is that WASI doesn't aspire to be portable to the web, and Emscripten's standard library only works on the web, whereas your system API is designed to be portable to both.

Yes I think that's a good way of putting it. Extism's primary goal is universality. I think the idea of having a plug-in system that is truly universal is exciting. Now we can share and maybe even sell plugins into different ecosystems. No more silo'd environments. I hope to see a future where standards can be built on top of this and plug-ins can outlive the applications themselves. Think VSTs if you are into music software.

That's interesting, one of examples that is challenging is a universal html template plugin. I'd love to try if it's feasible. Basically it should be logic less like Liquid. The unsure part is the custom tag, can it be called by host or not.

How do you define a universal html template plugin? Doesn't <template> already fit the bill?

The HTTP examples are fine, but a lower-level network module would enable all sorts of amazing plugins like a JDBC style ecosystem (WDBC?).

Oh, this is really exciting!

> I'm trying to figure out what Extism is actually providing here.

I'm trying to figure out if people really need compile to WASM/WASI -> run it back in a WASM runtime.

People don't. I see dead projects. This will be abandoned within a year.

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