Stream: git-wasmtime

Topic: wasmtime / issue #9205 Add WASI apis to async component

Wasmtime GitHub notifications bot (Sep 06 2024 at 14:03):

seogrady opened issue #9205:

Hello :wave: I'm new to wasmtime and have some questions after going through the examples. It looks like wasi-common is being deprecated in favor of wasmtime-wasi. There's a few different options such as wasmtime_wasi, wasmtime_wasi::preview0 and wasmtime_wasi::preview1. You can build a wasi_ctx with WasiCtxBuilder::new().build() or WasiCtxBuilder::new().build_p1(). Is there an example component using the latest preview?

I've managed to convert the provided component example from wasi-common to use wasmtime_wasi with async enabled.

bindgen!({
    world: "convert",
    path: "../wasi-component/wit",
    // tracing: true,
    async: {
        only_imports: [],
    },
    trappable_imports: true,
    require_store_data_send: true,
});

What do I need to do in order to get basic APIs working like stdio? I've tried adding inherit_stdio WasiCtxBuilder::new().inherit_stdio().build() to WasiCtxBuilder. Do I need to specify in the WIT file as well? :folded_hands:

Wasmtime GitHub notifications bot (Sep 06 2024 at 17:53):

alexcrichton commented on issue #9205:

There are some examples in the documentation of the wasmtime-wasi crate throughout various functions such as add_to_linker_async. Does that satisfy what you need? Or is there something else you're curious about?

Wasmtime GitHub notifications bot (Sep 07 2024 at 05:59):

seogrady commented on issue #9205:

Hey @alexcrichton! Thanks for your response. I've managed to implement the example from crates/wasi/src/bindings.rs and I'm calling my_custom_function from the host side that prints "Hello from host!".

This is my host file:

use wasmtime::{
    component::{bindgen, Component, Linker},
    Config, Engine, Result, Store,
};
use wasmtime_wasi::{ResourceTable, WasiCtx, WasiCtxBuilder, WasiView};

// Generate bindings of the guest and host components.
bindgen!({
    world: "my-world",
    path: "../wasi-component/wit",
    with: {
        "wasi": wasmtime_wasi::bindings,
    },
    async: true,
});

struct MyState {
    table: ResourceTable,
    ctx: WasiCtx,
}

#[async_trait::async_trait]
impl example::wasi::custom_host::Host for MyState {
    async fn my_custom_function(&mut self) {
        println!("Hello from host!");
    }
}

impl WasiView for MyState {
    fn table(&mut self) -> &mut ResourceTable {
        &mut self.table
    }
    fn ctx(&mut self) -> &mut WasiCtx {
        &mut self.ctx
    }
}

#[tokio::main]
async fn main() -> Result<()> {
    let mut config = Config::default();
    config.async_support(true);
    let engine = Engine::new(&config)?;
    let mut linker: Linker<MyState> = Linker::new(&engine);
    wasmtime_wasi::add_to_linker_async(&mut linker)?;
    example::wasi::custom_host::add_to_linker(&mut linker, |state| state)?;

    let component = Component::from_file(&engine, "crates/wasi-component/wasm/component.wasm")?;
    let mut store = Store::new(
        &engine,
        MyState {
            table: ResourceTable::new(),
            ctx: WasiCtxBuilder::new().inherit_stdio().build(),
        },
    );

    let command = MyWorld::instantiate_async(&mut store, &component, &linker).await?;
    let program_result = command.wasi_cli_run().call_run(&mut store).await?;

    match program_result {
        Ok(()) => Ok(()),
        Err(()) => std::process::exit(1),
    }
}

And this is the component:

wit_bindgen::generate!({
    world: "my-world",
    generate_all
});

use example::wasi::custom_host::my_custom_function;

use crate::exports::wasi::cli::run::Guest;

struct GuestComponent;

export!(GuestComponent);

impl Guest for GuestComponent {
    fn run() -> Result<(), ()> {
        my_custom_function();
        println!("Hello world");
        Ok(())
    }
}

When I run the program I get "Hello from host!". How can I use println! from the component?

Wasmtime GitHub notifications bot (Sep 07 2024 at 11:54):

seogrady closed issue #9205:

Hello :wave: I'm new to wasmtime and have some questions after going through the examples. It looks like wasi-common is being deprecated in favor of wasmtime-wasi. There's a few different options such as wasmtime_wasi, wasmtime_wasi::preview0 and wasmtime_wasi::preview1. You can build a wasi_ctx with WasiCtxBuilder::new().build() or WasiCtxBuilder::new().build_p1(). Is there an example component using the latest preview?

I've managed to convert the provided component example from wasi-common to use wasmtime_wasi with async enabled.

bindgen!({
    world: "convert",
    path: "../wasi-component/wit",
    // tracing: true,
    async: {
        only_imports: [],
    },
    trappable_imports: true,
    require_store_data_send: true,
});

What do I need to do in order to get basic APIs working like stdio? I've tried adding inherit_stdio WasiCtxBuilder::new().inherit_stdio().build() to WasiCtxBuilder. Do I need to specify in the WIT file as well? :folded_hands:

Wasmtime GitHub notifications bot (Sep 07 2024 at 11:54):

seogrady commented on issue #9205:

:relieved: Got there in the end. I needed to compile with target wasm32-wasip1, rather than wasm32-unknown-unknown. Missed that step when converting the component example to use wasmtime_wasi from wasi_common :+1:

Last updated: Dec 23 2024 at 12:05 UTC