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https://github.com/containerd/runwasi

Facilitates running Wasm / WASI workloads managed by containerd
https://github.com/containerd/runwasi

containerd kubernetes rust wasi wasm webassembly

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Facilitates running Wasm / WASI workloads managed by containerd

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README 

        
![runwasi logo light mode](./art/logo/runwasi_icon1.svg#gh-light-mode-only)

![runwasi logo dark mode](./art/logo/runwasi_icon3.svg#gh-dark-mode-only)



# runwasi



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



- If you haven't joined the CNCF slack yet, you can do so [here](https://slack.cncf.io/).

- Come join us on our [slack channel #runwasi](https://cloud-native.slack.com/archives/C04LTPB6Z0V)

on the CNCF slack.

- Public Community Call on Tuesdays every other week at 9:00 AM PT: [Zoom](https://zoom.us/my/containerd?pwd=bENmREpnSGRNRXdBZWV5UG8wbU1oUT09), [Meeting Notes](https://docs.google.com/document/d/1aOJ-O7fgMyRowHD0kOoA2Z_4d19NyAvvdqOkZO3Su_M/edit?usp=sharing)



## Usage



runwasi is intended to be consumed as a library to be linked to from your own wasm host implementation. It creates one shim process per container or k8s pod.



You need to implement a trait to teach runwasi how to use your wasm host.



There are two ways to do this:

* implementing the `sandbox::Instance` trait

* or implementing the `container::Engine` trait



The most flexible but complex is the `sandbox::Instance` trait:



```rust

pub trait Instance {

    /// The WASI engine type

    type Engine: Send + Sync + Clone;



    /// Create a new instance

    fn new(id: String, cfg: &InstanceConfig) -> Self;

    /// Start the instance

    /// The returned value should be a unique ID (such as a PID) for the instance.

    /// Nothing internally should be using this ID, but it is returned to containerd where a user may want to use it.

    fn start(&self) -> Result;

    /// Send a signal to the instance

    fn kill(&self, signal: u32) -> Result<(), Error>;

    /// Delete any reference to the instance

    /// This is called after the instance has exited.

    fn delete(&self) -> Result<(), Error>;

    /// Wait for the instance to exit

    /// The waiter is used to send the exit code and time back to the caller

    /// Ideally this would just be a blocking call with a normal result, however

    /// because of how this is called from a thread it causes issues with lifetimes of the trait implementer.

    fn wait(&self, waiter: &Wait) -> Result<(), Error>;

}

```



The `container::Engine` trait provides a simplified API:



```rust

pub trait Engine: Clone + Send + Sync + 'static {

    /// The name to use for this engine

    fn name() -> &'static str;

    /// Run a WebAssembly container

    fn run_wasi(&self, ctx: &impl RuntimeContext, stdio: Stdio) -> Result;

    /// Check that the runtime can run the container.

    /// This checks runs after the container creation and before the container starts.

    /// By default it checks that the wasi_entrypoint is either:

    /// * a OCI image with wasm layers

    /// * a file with the `wasm` filetype header

    /// * a parsable `wat` file.

    fn can_handle(&self, ctx: &impl RuntimeContext) -> Result<()> { /* default implementation*/ }

}

```



After implementing `container::Engine` you can use `container::Instance`, which implements the `sandbox::Instance` trait.



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



```rust

use containerd_shim as shim;

use containerd_shim_wasm::sandbox::{ShimCli, Instance}



struct MyInstance {

    // ...

}



impl Instance for MyInstance {

    // ...

}



fn main() {

    shim::run::>("io.containerd.myshim.v1", opts);

}

```



or when using the `container::Engine` trait, like this:



```rust

use containerd_shim as shim;

use containerd_shim_wasm::{sandbox::ShimCli, container::{Instance, Engine}}



struct MyEngine {

    // ...

}



impl Engine for MyEngine {

    // ...

}



fn main() {

    shim::run::>>("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`.



Check out these projects that build on top of runwasi:

- [spinkube/containerd-shim-spin](https://github.com/spinkube/containerd-shim-spin)

- [deislabs/containerd-wasm-shims](https://github.com/deislabs/containerd-wasm-shims)



### Components



- **containerd-shim-[ wasmedge | wasmtime | wasmer | wamr ]-v1**



This is a containerd shim which runs wasm workloads in [WasmEdge](https://github.com/WasmEdge/WasmEdge) or [Wasmtime](https://github.com/bytecodealliance/wasmtime) or [Wasmer](https://github.com/wasmerio/wasmer).

You can use it with containerd's `ctr` by specifying `--runtime=io.containerd.[ wasmedge | wasmtime | wasmer | wamr ].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.



## Demo



### Installing the shims for use with Containerd



Make sure you have [installed dependencies](./CONTRIBUTING.md#setting-up-your-local-environment) and install the shims:



```terminal

make build

sudo make install

```



> Note: `make build` will only build one binary. The `make install` command copies the binary to $PATH and uses symlinks to create all the component described above.



Pull the test image:



```

make pull-app

```



### Demo 1 using container image that contains a Wasm module.



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



```terminal

sudo ctr run --rm --runtime=io.containerd.wasmtime.v1 ghcr.io/containerd/runwasi/wasi-demo-app: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, you can run in other session: `sudo ctr task kill -s SIGKILL testwasm`.



The test binary supports commands for different type of functionality, check [crates/wasi-demo-app/src/main.rs](crates/wasi-demo-app/src/main.rs) to try it out.



### Demo 2 using OCI Images with custom WASM layers



The previous demos run with an OCI Container image containing the wasm module in the file system.  Another option is to provide a cross-platform OCI Image that that will not have the wasm module or components in the file system of the container that wraps the wasmtime/wasmedge process.  This OCI Image with custom WASM layers can be run across any platform and provides for de-duplication in the Containerd content store among other benefits. To build OCI images using your own images you can use the [oci-tar-builder](./crates/oci-tar-builder/README.md)



To learn more about this approach checkout the [design document](https://docs.google.com/document/d/11shgC3l6gplBjWF1VJCWvN_9do51otscAm0hBDGSSAc/edit).



> **Note**: This requires containerd 1.7.7+ and 1.6.25+.  If you do not have these patches for both `containerd` and `ctr` you will end up with an error message such as `mismatched image rootfs and manifest layers` at the import and run steps. Latest versions of k3s and kind have the necessary containerd versions.



Pull the OCI image with WASM layers image:



```

make pull

```



Run the image with `sudo ctr run --rm --runtime=io.containerd.[ wasmedge | wasmtime | wasmer | wamr ].v1 ghcr.io/containerd/runwasi/wasi-demo-oci:latest testwasmoci`



```

sudo ctr run --rm --runtime=io.containerd.wasmtime.v1 ghcr.io/containerd/runwasi/wasi-demo-oci:latest testwasmoci wasi-demo-oci.wasm echo 'hello'

hello

exiting

```



### Demo 3 using Wasm OCI Artifact



The [CNCF tag-runtime wasm working group](https://tag-runtime.cncf.io/wgs/wasm/charter/) has a [OCI Artifact format for Wasm](https://tag-runtime.cncf.io/wgs/wasm/deliverables/wasm-oci-artifact/).  This is a new Artifact type that enable the usage across projects beyond just runwasi, see the https://tag-runtime.cncf.io/wgs/wasm/deliverables/wasm-oci-artifact/#implementations



```

make test/k8s-oci-wasmtime

```



> note: We are using a kubernetes cluster to run here since containerd's ctr has a bug that results in ctr: `unknown image config media type application/vnd.wasm.config.v0+json`



### Demo 4: Running on Kubernetes



You can run WebAssembly workloads on Kubernetes using either Kind or k3s.



#### Using Kind



1. Install and configure dependencies:

```bash

curl -Lo ./kind https://kind.sigs.k8s.io/dl/v0.21.0/kind-linux-amd64

chmod +x ./kind

sudo mv ./kind /usr/local/bin/



make build-wasmtime

sudo make install-wasmtime

```



2. Create a Kind configuration:

```yaml

# kind-config.yaml

kind: Cluster

apiVersion: kind.x-k8s.io/v1alpha4

name: runwasi-cluster

nodes:

- role: control-plane

  extraMounts:

  - hostPath: /usr/local/bin/containerd-shim-wasmtime-v1

    containerPath: /usr/local/bin/containerd-shim-wasmtime-v1

```



3. Create and configure the cluster:

```bash

kind create cluster --name runwasi-cluster --config kind-config.yaml



kubectl cluster-info --context kind-runwasi-cluster



cat << EOF | docker exec -i runwasi-cluster-control-plane tee /etc/containerd/config.toml

[plugins."io.containerd.grpc.v1.cri".containerd.runtimes.wasm]

  runtime_type = "io.containerd.wasmtime.v1"

EOF



docker exec runwasi-cluster-control-plane systemctl restart containerd

```



4. Deploy the demo application:

```bash

kubectl --context kind-runwasi-cluster apply -f test/k8s/deploy.yaml

```



5. Check the logs:

```bash

kubectl --context kind-runwasi-cluster logs -l app=wasi-demo

```

where you should see the output of the demo application: 



```console

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...

```



#### Using k3s



1. Install k3s and build the shim:

```bash

curl -sfL https://get.k3s.io | sh -



make build-wasmtime

sudo make install-wasmtime

```



2. Configure k3s to use the Wasm runtime:

```bash

sudo mkdir -p /var/lib/rancher/k3s/agent/etc/containerd/



cat << EOF | sudo tee -a /var/lib/rancher/k3s/agent/etc/containerd/config.toml.tmpl

[plugins."io.containerd.grpc.v1.cri".containerd.runtimes.wasm]

  runtime_type = "io.containerd.wasmtime.v1"

EOF



sudo systemctl restart k3s

```



3. Deploy the demo application:

```bash

sudo k3s kubectl apply -f test/k8s/deploy.yaml

```



4. Check the deployment:

```bash

sudo k3s kubectl wait deployment wasi-demo --for condition=Available=True --timeout=90s



sudo k3s kubectl get pods

sudo k3s kubectl logs -l app=wasi-demo

```



You should see "This is a song that never ends." repeated in the logs.



5. Clean up when done:

```bash

sudo k3s kubectl delete -f test/k8s/deploy.yaml



# Optionally uninstall k3s

/usr/local/bin/k3s-uninstall.sh

```



#### The `deploy.yaml` file



The deployment includes:

```yaml

apiVersion: node.k8s.io/v1

kind: RuntimeClass

metadata:

  name: wasm

handler: wasm

---

apiVersion: apps/v1

kind: Deployment

metadata:

  name: wasi-demo

spec:

  # ...

  template:

    spec:

      runtimeClassName: wasm # Use the wasm runtime class

      containers:

      - name: demo

        image: ghcr.io/containerd/runwasi/wasi-demo-app:latest

```



To see demos for other runtimes, replace `wasmtime` with `wasmedge`, `wasmer`, or `wamr` in the above commands.



In addition, check out the [Kubernetes + Containerd + Runwasi](https://wasmedge.org/docs/develop/deploy/kubernetes/kubernetes-containerd-runwasi) for more on how to run WasmEdge on Kubernetes. 



### WASI/HTTP Demo for `wasmtime-shim`

See [wasmtime-shim documentation](./crates/containerd-shim-wasmtime/README.md#WASI/HTTP).



## Contributing



To begin contributing, learn to build and test the project or to add a new shim please read our [CONTRIBUTING.md](./CONTRIBUTING.md)