workers-rs VS WASI

- The speed of the Python interpreter running in WebAssembly

Today, Python cold starts are slower than cold starts for a JavaScript Worker of equivalent size. A basic "Hello World" Worker written in JavaScript has a near zero cold start time, while a Python Worker has a cold start under 1 second.

That's because we still need to load Pyodide into your Worker on-demand when a request comes in. The blog post describes what we're working on to reduce this — making Pyodide already available upfront.

Once a Python Worker has gone through a cold start though, the differences are more on the margins — maybe a handful milliseconds, depending on what happens during the request.

- There is a slight cost (think — microseconds not milliseconds) to crossing the "bridge" between JavaScript and WebAssembly — for example, by performing I/O or async operations. This difference tends to be minimal — generally something measured in microseconds not milliseconds. People with performance sensitive Workers already write them in Rust https://github.com/cloudflare/workers-rs, which also relies on bridging between JavaScript and WebAssembly.

- The Python interpreter that Pyodide provides, that runs in WebAssembly, isn't as fast as the years and years of optimization that have gone into making JavaScript fast in V8. But it's still relatively early days for Pyodide, compared to the JS engine in V8 — there are parts of its code where we think there are big perf gains to be had. We're looking forward to upstreaming performance improvements, and there are WebAssembly proposals that help here too.

Not yet, but we're working on that https://github.com/cloudflare/workers-rs/pull/324

I'm also in the Workers org but I have had a bit of interaction with Rust. There's some Rust in the Workers runtime using lol-html for HTMLRewriter as well as some tooling and there's the full blown workers-rs framework that I work on, but that's about it for the Rust I work on regularly.

I'm an engineer at Cloudflare working on Workers (and a maintainer of workers-rs) and I'd love to help whoever ends up maintaining this get that PR rewriting it in Rust across the line.

GitHub - cloudflare/workers-rs: Write Cloudflare Workers in 100% Rust via WebAssembly

I never said it was, but thankfully nowadays there are plenty of other tools that are fast enough to keep the dev cycle quick. Personally esbuild is my go-to when I need a bundler but I've grown really fond of SWC native api, we used to use it at work for our wasm build tool for our workers-rs framework.

There's actually a rust framework for Workers https://github.com/cloudflare/workers-rs

I'm a maintainer of the of the Cloudflare workers-rs project to allow you to write serverless functions in Rust running as WASM in our V8-based runtime. There's certainly some rough spots (doesn't have complete parity with our default JS runtime apis), but if you're concerned with cold start times and you don't need a full containerized environment I think it's a solid choice.

Most likely, it should, we just haven't had the time to fully implement it or add a library to wrap the FFI. Please let us know you need a feature by opening an issue.

I may be biased, as the original project author, but I’d recommend using Cloudflare Workers https://github.com/cloudflare/workers-rs - totally free their with very generous limits.

WASI Co-chair here. Nothing in WASI is "somehow blocked by Google", or indeed blocked by anyone at all. Graphics support in WASI hasn't been developed simply because nobody has put energy into developing graphics support in WASI.

At the end of 2023 we counted around 40 contributors who have been working on WASI specifications and implementations: https://github.com/WebAssembly/meetings/blob/main/wasi/2023/... . That is a great growth for our project from a few years ago when that issue was filed, but as you can see from what people are working on, its all much more foundational pieces than a graphics interface. Also, if you look at who is employing those contributors, its largely vendors who are interested in WASI in the context of serverless. That doesn't mean WASI is limited to only serverless, but that has been the focus from contributors so far.

By rolling out WASI on top of the WASM Component Model we have built a sound foundation for creating WASI proposals that support more problem domains, such as embedded systems (@mc_woods and his colleagues are helping with this), or graphics if someone is interested in putting in the work. Our guide to how to create proposals is found here: https://github.com/WebAssembly/WASI/blob/main/Contributing.m... .

> As I understand it, it's not even really possible today to make WebAssembly do anything meaningful in the browser without trampolining back out to JavaScript anyway, which seems like a remarkable missed opportunity.

That's the underlying messy API it's built on. There are specs to make the API more standardized like https://github.com/WebAssembly/WASI

But overall, yeah, it feels like a shiny new toy everyone is excited about and wants to use. Some toys can be fun to play with, but it doesn't mean we have to rewrite production systems in it. Sometimes, or most of the time, toys don't become useful tools.

Snapshot Preview 1 is the standard all tools are building to right now. The specification is available here: https://github.com/WebAssembly/WASI/blob/main/legacy/preview...

It's pretty unreadable though!

Preview 2 looks like it will be a big change, and is just being finalised at the moment. I'd expect that when preview 2 is available there will be an improvement in the quality of documentation. I'm not sure how long it will take after release for tools to start switching to it. I'd expect Preview 1 will still be the main target at least for the rest of this year.

> Like WTF does this mean? The repo tells me nothing

Directly above the sentence you quoted:

"Interposition in the context of WASI interfaces is the ability for a Webassembly instance to implement a given WASI interface, and for a consumer WebAssembly instance to be able to use this implementation transparently. This can be used to adapt or attenuate the functionality of a WASI API without changing the code using it."

> and I've still yet to see a clear write-up about what WASI is.

In the same document: [0]

> WTF is wit?

The first link in that document ("Starting in Preview2, WASI APIs are defined using the Wit IDL.") is [1].

> I click on "legacy" and I see preview0 and preview1, which are basically unreadable proto-specs.

The README for the legacy directory [2] clearly explains what they are.

> Where's a single well-written WASI spec?

"Development of each API happens in its own repo, which you can access from the proposals list." [3]

> Whatever WASI is doing, I don't like it.

Clearly not - you've gone out of your way to ignore all of the documentation that answers your questions.

> And neither does AssemblyScript team apparently

The AssemblyScript team have a bone to pick with WASI based on their misunderstanding of what WASI is for (it is not intended for use on the web) and WASI's disinterest in supporting UTF-16 strings. You can see for yourself in [4].

[0]: https://github.com/WebAssembly/WASI/tree/main#wasi-high-leve...

The Bytecode Alliance initiated a sub-project called the WebAssembly System Interface (WASI). WASI is an API that allows WebAssembly access to system features such as files, filesystems, Berkeley sockets, clocks, and random numbers. WASI acts as a system-level interface for WebAssembly, so incorporating a runtime into a host environment and building a platform is easier.

We are excited to contribute back to Wasmtime and the component model, as well as to new projects and proposals emerging in this space (such as new Wasm proposals, like WASI Preview 2, wasi-keyvalue, wasi-sql or wasi-cloud).

I've been reading the following repositories.

https://github.com/WebAssembly/WASI/blob/main/Proposals.md