Allow configuration of wasmtime features

[tanishiking]

Currently, containerd-shim-wasmtime-v1 doesn't seem to be able to configure the underlying wasmtime runtime.

runwasi/crates/containerd-shim-wasmtime/src/instance.rs

Lines 67 to 82 in 7a9c892

	// Disable Wasmtime parallel compilation for the tests
	// see https://github.com/containerd/runwasi/pull/405#issuecomment-1928468714 for details
	config.parallel_compilation(!cfg!(test));
	config.wasm_component_model(true); // enable component linking
	config.async_support(true); // must be on
	if use_pooling_allocator_by_default() {
	let cfg = wasmtime::PoolingAllocationConfig::default();
	config.allocation_strategy(wasmtime::InstanceAllocationStrategy::Pooling(cfg));
	}
	Self {
	engine: wasmtime::Engine::new(&config)
	.context("failed to create wasmtime engine")
	.unwrap(),
	cancel: CancellationToken::new(),

This limitation prevent us from running our Wasm OCI artifact, built from component binary that requires -W function-references,gc unable to run on the shim. (on k8s, it ends up with CrashLoopBackOff).

https://github.com/users/tanishiking/packages/container/package/scala-wasm-echo-server (Wasm OCI artifact built by wkg oci push from Wasm component binary that implements wasi:http/proxy)

https://github.com/scala-wasm/scala-wasm/tree/scala-wasm/examples/echo-server

Is there a way to configure wasmtime from runwasi?

[Mossaka]

Is there a way to configure wasmtime from runwasi?

Unfortunately no, the current wasmtime shim does not support configuration.

I think this issue #847 might be relevant, and we need a design on how to propogate the configuration to the wasmtime shim. Just to throw some ideas: One way of doing it is to modify containerd's config.toml to add to the CRI options but obviously this won't work with non-CRI runtimes. Another way is to bundle the wasmtime config file in the OCI artifact and when runwasi parses it, it uses the config file to configure wasmtime at runtime.

In the meantime, feel free to modify the source code to add the features you need.

[Mossaka]

Btw, the Scala wasi-http component is really cool, @tanishiking !!

[tanishiking]

Thanks @Mossaka! runwasi to parse wasmtime config file sounds good.

I feel it looks right for the container runtime to handle configuration options, rather than embedding those settings within the OCI artifact, maybe through pod volume or something?

Anyway, I'll add some options to wasmtime in local build for the time being.