runwasi

Warning: Alpha quality software, do not use in production.

This is a project to facilitate running wasm workloads managed by containerd either directly (ie. through ctr) or as directed by Kubelet via the CRI plugin. It is intended to be a (rust) library that you can take and integrate with your wasm host. Included in the repository is a PoC for running a plain wasi host (ie. no extra host functions except to support wasi system calls).

Community

Come join us on our slack channel #runwasi on the CNCF slack.

Usage

runwasi is intended to be consumed as a library to be linked to from your own wasm host implementation.

There are two modes of operation supported:

1. "Normal" mode where there is 1 shim process per container or k8s pod.
2. "Shared" mode where there is a single manager service running all shims in process.

In either case you need to implement the Instance trait:

pub trait Instance {
    // Create a new instance
    fn new(id: String, cfg: Option<&InstanceConfig<Self::E>>) -> Self;
    // Start the instance and return the pid
    fn start(&self) -> Result<u32, Error>;
    // Send the specified signal to the instance
    fn kill(&self, signal: u32) -> Result<(), Error>;
    // Delete the instance
    fn delete(&self) -> Result<(), Error>;
    // wait for the instance to exit and send the exit code and exit timestamp to the provided sender.
    fn wait(&self, send: Sender<(u32, DateTime<Utc>)>) -> Result<(), Error>;
}

To use your implementation in "normal" mode, you'll need to create a binary which has a main that looks something like this:

use containerd_shim as shim;
use containerd_shim_wasm::sandbox::{ShimCli, Instance}

struct MyInstance {
 // ...
}

impl Instance for MyInstance {
    // ...
}

fn main() {
    shim::run::<ShimCli<MyInstance>>("io.containerd.myshim.v1", opts);
}

Note you can implement your own ShimCli if you like and customize your wasm engine and other things. I encourage you to checkout how that is implemented.

The shim binary just needs to be installed into $PATH (as seen by the containerd process) with a binary name like containerd-shim-myshim-v1.

For the shared mode:

use containerd_shim_wasm::sandbox::{Local, ManagerService, Instance};
use containerd_shim_wasm::services::sandbox_ttrpc::{create_manager, Manager};
use std::sync::Arc;
use ttrpc::{self, Server};
/// ...

struct MyInstance {
    /// ...
}

impl Instance for MyInstance {
    // ...
}

fn main() {
    let s: ManagerService<Local<MyInstance>> =
        ManagerService::new(Engine::new(Config::new().interruptable(true)).unwrap());
    let s = Arc::new(Box::new(s) as Box<dyn Manager + Send + Sync>);
    let service = create_manager(s);

    let mut server = Server::new()
        .bind("unix:///run/io.containerd.myshim.v1/manager.sock")
        .unwrap()
        .register_service(service);

    server.start().unwrap();
    let (_tx, rx) = std::sync::mpsc::channel::<()>();
    rx.recv().unwrap();
}

This will be the host daemon that you startup and manage on your own. You can use the provided containerd-shim-myshim-v1 binary as the shim to specify in containerd.

Shared mode requires precise control over real threads and as such should not be used with an async runtime.

Examples

Components

• containerd-shim-[ wasmedge | wasmtime ]-v1

This is a containerd shim which runs wasm workloads in WasmEdge or Wasmtime. You can use it with containerd's ctr by specifying --runtime=io.containerd.[ wasmedge | wasmtime ].v1 when creating the container. And make sure the shim binary must be in $PATH (that is the $PATH that containerd sees). Usually you just run make install after make build.

build shim with wasmedge we need install library first

This shim runs one per pod.

• containerd-shim-[ wasmedge | wasmtime ]d-v1

A cli used to connect containerd to the containerd-[ wasmedge | wasmtime ]d sandbox daemon. When containerd requests for a container to be created, it fires up this shim binary which will connect to the containerd-[ wasmedge | wasmtime ]d service running on the host. The service will return a path to a unix socket which this shim binary will write back to containerd which containerd will use to connect to for shim requests. This binary does not serve requests, it is only responsible for sending requests to the contianerd-[ wasmedge | wasmtime ]d daemon to create or destroy sandboxes.

• containerd-[ wasmedge | wasmtime ]d

This is a sandbox manager that enables running 1 wasm host for the entire node instead of one per pod (or container). When a container is created, a request is sent to this service to create a sandbox. The "sandbox" is a containerd task service that runs in a new thread on its own unix socket, which we return back to containerd to connect to.

The Wasmedge / Wasmtime engine is shared between all sandboxes in the service.

To use this shim, specify io.containerd.[ wasmedge | wasmtime ]d.v1 as the runtime to use. You will need to make sure the containerd-[ wasmedge | wasmtime ]d daemon has already been started.

Test and demo with containerd

Attention

Instead of enabling docker-desktop official released feature use containerd for pulling and storing images, you can build a local image and interact with the container locally.

• Install WasmEdge first (If you choose Wasmedge as your wasm runtime)

  • Install WasmEdge
  • Make sure the library is in the search path.

$ curl -sSf https://raw.githubusercontent.com/WasmEdge/WasmEdge/master/utils/install.sh | bash
$ sudo -E sh -c 'echo "$HOME/.wasmedge/lib" > /etc/ld.so.conf.d/libwasmedge.conf'
$ sudo ldconfig

• Run unit test

$ cargo test -- --nocapture

You should see some output like:

running 3 tests
test instance::tests::test_maybe_open_stdio ... ok
test instance::wasitest::test_delete_after_create ... ok
test instance::wasitest::test_wasi ... ok

• Build and install shim components

$ make build
$ sudo make install

• Demo

Now you can use the test image provided in this repo to have test with, use make load to load it into containerd.

• Case 1.

Run it with sudo ctr run --rm --runtime=io.containerd.[ wasmedge | wasmtime ].v1 ghcr.io/containerd/runwasi/wasi-demo-app:latest testwasm /wasi-demo-app.wasm echo 'hello'. You should see some output repeated like:

$ sudo ctr run --rm --runtime=io.containerd.wasmedge.v1 ghcr.io/containerd/runwasi/wasi-demo-app:latest testwasm /wasi-demo-app.wasm echo 'hello'

hello
exiting

• Case 2.

Run it with sudo ctr run --rm --runtime=io.containerd.[ wasmedge | wasmtime ].v1 docker.io/library/wasmtest:latest testwasm. You should see some output repeated like:

$ sudo ctr run --rm --runtime=io.containerd.wasmedge.v1 docker.io/library/wasmtest:latest testwasm

This is a song that never ends.
Yes, it goes on and on my friends.
Some people started singing it not knowing what it was,
So they'll continue singing it forever just because...

This is a song that never ends.
Yes, it goes on and on my friends.
Some people started singing it not knowing what it was,
So they'll continue singing it forever just because...

(...)

To kill the process from the case 2. demo, you can run in other session: sudo ctr task kill -s SIGKILL testwasm. And the test binary supports full commands, check test/image/src/main.rs to play around more.