How to use Rust SDK in an async/tokio runtime? about extism

[milesj]

Closing this since it works now in 0.4!

[nilslice]

This might be relevant: https://users.rust-lang.org/t/solved-how-to-move-non-send-between-threads-or-an-alternative/19928/7

Sorry, only have time for a quick review but thought that link might be helpful - can dig in more soon. But plugins have their own mutable memory used to persist plugin data between function calls. See https://extism.org/docs/write-a-plugin/rust-pdk/#using-config-io--persisted-variables

Can you create a new plugin context & plugin per spawned task / thread?

[jcswart]

I have been experimenting with extism and tokio.

The first such experiment, in an axum program was the following. NOTE: This is all experimental code. Its just meant to provide a slightly more concrete example than simply saying, "use a once_cell". https://docs.rs/once_cell/latest/once_cell/

struct PluginManager {}

impl PluginManager {
    fn run(&self, input: String) -> String {
        let wasm = std::fs::read("src/code.wasm").unwrap();
        let context = Context::new();
        let mut plugin = Plugin::new(&context, wasm, vec![], true).unwrap();

        let data = plugin.call("count_vowels", &input).unwrap();

        String::from_utf8(data.to_vec()).unwrap_or("error".to_string())
    }
}

Then in main.rs:

static PLUGIN_MANAGER: OnceCell<PluginManager> = OnceCell::new();

And before I start the axum server:

let _ = PLUGIN_MANAGER.set(PluginManager {});

Now in any route I can simply:

let plugins = PLUGIN_MANAGER.get().expect("failed to get plugin manager, was it set?");
let result = plugins.run("input");

The next experiment is to update the PluginManager to separate plugin compilation from execution. If there isn't an obvious way to do this with the once_cell alone I will likely incorporate a https://github.com/xacrimon/dashmap as they allow you to safely update across threads.

[milesj]

Yeah I was thinking of using a similar approach. Basically have a plugin registry singleton using OnceCell.

[bhelx]

Thanks for following up!