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Kubernetes + Containerd + Runwasi

Quick start​

The GitHub repo contains scripts and GitHub Actions for running our example apps on Kubernetes + containerd + runwasi.

In the rest of this section, we will explain the steps in detail.

Prerequisites for this setup​

Please ensure that you have completed the following steps before proceeding with this setup.

Install and start Kubernetes​

Run the following commands from a terminal window. It sets up Kubernetes for local development.

# Install go
$ wget https://golang.org/dl/go1.17.1.linux-amd64.tar.gz
$ sudo rm -rf /usr/local/go
$ sudo tar -C /usr/local -xzf go1.17.1.linux-amd64.tar.gz
$ source /home/${USER}/.profile

# Clone k8s
$ git clone https://github.com/kubernetes/kubernetes.git
$ cd kubernetes
$ git checkout v1.22.2

# Install etcd with hack script in k8s
$ sudo CGROUP_DRIVER=systemd CONTAINER_RUNTIME=remote CONTAINER_RUNTIME_ENDPOINT='unix:///var/run/containerd/containerd.sock' ./hack/install-etcd.sh
$ export PATH="/home/${USER}/kubernetes/third_party/etcd:${PATH}"
$ sudo cp third_party/etcd/etcd* /usr/local/bin/

# After run the above command, you can find the following files: /usr/local/bin/etcd  /usr/local/bin/etcdctl  /usr/local/bin/etcdutl

# Build and run k8s with containerd
$ sudo apt-get install -y build-essential
$ sudo CGROUP_DRIVER=systemd CONTAINER_RUNTIME=remote CONTAINER_RUNTIME_ENDPOINT='unix:///var/run/containerd/containerd.sock' ./hack/local-up-cluster.sh

... ...
Local Kubernetes cluster is running. Press Ctrl-C to shut it down.

Do NOT close your terminal window. Kubernetes is running!

Run and test the Kubernetes Cluster​

Finally, we can run WebAssembly programs in Kubernetes as containers in pods. In this section, we will start from another terminal window and start using the cluster.

export KUBERNETES_PROVIDER=local

sudo cluster/kubectl.sh config set-cluster local --server=https://localhost:6443 --certificate-authority=/var/run/kubernetes/server-ca.crt
sudo cluster/kubectl.sh config set-credentials myself --client-key=/var/run/kubernetes/client-admin.key --client-certificate=/var/run/kubernetes/client-admin.crt
sudo cluster/kubectl.sh config set-context local --cluster=local --user=myself
sudo cluster/kubectl.sh config use-context local
sudo cluster/kubectl.sh

Let's check the status to make sure that the cluster is running.

$ sudo cluster/kubectl.sh cluster-info

# Expected output
Cluster "local" set.
User "myself" set.
Context "local" created.
Switched to context "local".
Kubernetes control plane is running at https://localhost:6443
CoreDNS is running at https://localhost:6443/api/v1/namespaces/kube-system/services/kube-dns:dns/proxy

To further debug and diagnose cluster problems, use 'kubectl cluster-info dump'.

Configure containerd and Kubernetes for Wasmedge Runtime​

Next we will configure containerd to add support for the containerd-shim-wasmedge. Please ensure that you have setup runwasi to work with WasmEdge container images.

# Run the following command as root user
sudo bash -c "containerd config default > /etc/containerd/config.toml"
echo '[plugins."io.containerd.grpc.v1.cri".containerd.runtimes.wasmedge] runtime_type = "io.containerd.wasmedge.v1"' | sudo tee -a /etc/containerd/config.toml > /dev/null
sudo systemctl restart containerd

Next we will create a RuntimeClass in Kubernetes to specify usage of wasmedge runtime for objects labeled as runtime=wasm

sudo cluster/kubectl.sh apply -f - <<< '{"apiVersion":"node.k8s.io/v1","kind":"RuntimeClass","metadata":{"name":"wasm"},"scheduling":{"nodeSelector":{"runtime":"wasm"}},"handler":"wasmedge"}'

Now we will label the kubernetes node as runtime=wasm. Note that the node where we changed the containerd configurations will be the one which we will label.

An example of how we can label the node is given below:

sudo cluster/kubectl.sh get nodes
# Sample output from the command above
NAME        STATUS     ROLES    AGE    VERSION
127.0.0.1   Ready   <none>   3h4m   v1.22.2
# Run the following command to label the node 
sudo cluster/kubectl.sh label nodes 127.0.0.1 runtime=wasm
# A successful output from the above command looks like this
node/127.0.0.1 labeled

A WebAssembly-based HTTP service​

A separate article explains how to compile, package, and publish a simple WebAssembly HTTP service application as a container image to Docker hub. Run the WebAssembly-based image from Docker Hub in the Kubernetes cluster as follows.

sudo cluster/kubectl.sh apply -f - <<< '{"apiVersion":"apps/v1","kind":"Deployment","metadata":{"name":"http-server-deployment"},"spec":{"replicas":1,"selector":{"matchLabels":{"app":"http-server"}},"template":{"metadata":{"labels":{"app":"http-server"}},"spec":{"hostNetwork":true,"runtimeClassName":"wasm","containers":[{"name":"http-server","image":"wasmedge/example-wasi-http:latest","ports":[{"containerPort":1234}]}]}}}}'

Since we are using hostNetwork in the kubectl run command, the HTTP server image is running on the local network with IP address 127.0.0.1. Now, you can use the curl command to access the HTTP service.

$ curl -d "name=WasmEdge" -X POST http://127.0.0.1:1234
echo: name=WasmEdge

That's it!