Loading WASM plugin using http-wasm without Go?

[mobileskyfi]

Not sure where to file this.

Just for fun, I've been tried building Traefik WASM plugin using Grain. I'm still working on the http-wasm binding and type-mapping, but it loads/runs as Grain-based WASM plugin from/pluginsLocal/src/grain/plugin.wasm.

While not ready to publish anything on the Traefik Plugin Catalog, I did add the "traefik-plugin" GitHub tag to this project: https://github.com/tikoci/traefik-wasm-grain with following .traefik.yml:

displayName: traefik-wasm-grain
type: middleware
runtime: wasm
iconPath: icon.png
summary: Experimental plugin using WASM and grain-lang.org, directly using http-wasm ABI
testData:
  Headers:
    Foo: Bar

And docs suggest I should have gotten an automated #3 "Plugin Analyzer ... problem" bug reports by virtue of the tag. But that never happened. I even added a tagged release to project – just to trigger something – since I'm not 100% the .traefik.yml is right.

Perhaps the "Plugin Catalog" also check to project type is "Go" – since GitHub flags tikoci/traefik-wasm-grain as a Makefile project?

Not urgent here. But be nice to know something could be published to avoid file copies/Dockerfile-mod/etc to "localPlugins".

[mobileskyfi]

I figure this out. It was the GitHub language.

Adding this in .gitattributes fix it:

# Grain is Go for Traefik
*.gr linguist-language=go

# see https://github.com/github-linguist/linguist/blob/master/docs/overrides.md

Since this project is kinda the only place where building a WASM plugin is documented, I filled it here. I don't know the traefik plumbing/process, my guess is piceus
searchQuery = "topic:traefik-plugin language:Go archived:false is:public"

While Grain is pretty esoteric, I'd imagine someone will build one of these in Rust/etc soon enough.

Perhaps there should be a new GitHub tag like "traefik-wasm-plugin" (or whatever)?

[nihaopaul]

I figure this out. It was the GitHub language.

Adding this in .gitattributes fix it:

Grain is Go for Traefik

*.gr linguist-language=go

see https://github.com/github-linguist/linguist/blob/master/docs/overrides.md

Since this project is kinda the only place where building a WASM plugin is documented, I filled it here. I don't know the traefik plumbing/process, my guess is piceus searchQuery = "topic:traefik-plugin language:Go archived:false is:public"

While Grain is pretty esoteric, I'd imagine someone will build one of these in Rust/etc soon enough.

Perhaps there should be a new GitHub tag like "traefik-wasm-plugin" (or whatever)?

Did you manage to find one? I've spent a few hours today trying to get rust version of wasm compiled and loaded. I've got the outline so far but trying to enable logging pass through but I'm a bit of a noob when it comes to rust so I'm also interested in examples: https://github.com/nihaopaul/traefik-rust-wasm-plugin

[mobileskyfi]

Did you manage to find one?

No, only Go examples for http-wasm ABI used by Traefik. Given you can already write a Traefik plugin in Go, the indirection of Go-based WASM is actually less useful... And... https://http-wasm.io only has the TinyGo example.

The underlying issue is that http-wasm that Traefik uses is not friendly with wasm-bindgen and/or wit-bindgen Rust likes... And with a .wit file... all this be easier in Rust, but the http-wasm folks seem to have philosophical problems with a .wit file... so you just get commented .wat file.

What this means is http-wasm ABI needs to be explicitly defined in Rust to be callable. So to make a log() call to http-wasm/Traefik from Rust...I think your code need some #[link()] things...

 #[link(wasm_import_module)]
extern log(level: i32, msg: i32, len: i32) 

And repeated for rest of thethe http-wasm ABI functions exposed by Traefik (or at least the ones you plan to use). This be similar to what I had to do for Grain so the the handler can perform operations like log() or set_header_value().

But since msg is a pointer, that also need to managed in your code. And all of which is why I didn't try, and my Rust knowledge is pretty superficial. But I did get Grain working, which largely involved mapping the .wat file, by hand. I added another high-level wrapper "extern" things to deal with marshaling strings to deal with this in Grain: https://github.com/tikoci/traefik-wasm-grain/tree/main

Also, you can use wasm2wat to see what Rust generated, and compare to the signatures in the .wat file from http-wasm - as they should look the same.

But...some Rust example be useful here — as noted, if you're writing Go, a real plugin would seem to be a better plan than WASM. You have some rust code you want to run, well, now WASM support be more useful in Traefik.

[nihaopaul]

Did you manage to find one?

No, only Go examples for http-wasm ABI used by Traefik. Given you can already write a Traefik plugin in Go, the indirection of Go-based WASM is actually less useful... And... https://http-wasm.io only has the TinyGo example.

The underlying issue is that http-wasm that Traefik uses is not friendly with wasm-bindgen and/or wit-bindgen Rust likes... And with a .wit file... all this be easier in Rust, but the http-wasm folks seem to have philosophical problems with a .wit file... so you just get commented .wat file.

What this means is http-wasm ABI needs to be explicitly defined in Rust to be callable. So to make a log() call to http-wasm/Traefik from Rust...I think your code need some #[link()] things...

 #[link(wasm_import_module)]
extern log(level: i32, msg: i32, len: i32) 

And repeated for rest of thethe http-wasm ABI functions exposed by Traefik (or at least the ones you plan to use). This be similar to what I had to do for Grain so the the handler can perform operations like log() or set_header_value().

But since msg is a pointer, that also need to managed in your code. And all of which is why I didn't try, and my Rust knowledge is pretty superficial. But I did get Grain working, which largely involved mapping the .wat file, by hand. I added another high-level wrapper "extern" things to deal with marshaling strings to deal with this in Grain: https://github.com/tikoci/traefik-wasm-grain/tree/main

Also, you can use wasm2wat to see what Rust generated, and compare to the signatures in the .wat file from http-wasm - as they should look the same.

But...some Rust example be useful here — as noted, if you're writing Go, a real plugin would seem to be a better plan than WASM. You have some rust code you want to run, well, now WASM support be more useful in Traefik.

Check out https://github.com/nihaopaul/traefik-rust-wasm-plugin/ I managed to spend a few days getting this to work. I use docker to load my wasm file once compiled. I've followed the http-wasm spec and made decisions such as dynamic buffers. And implemented the i32/i64s as per spec not the signed integers.