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Kubernetes + containerd + crun

Quick start​

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

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

We assume you have already installed and configured containerd to work with WasmEdge container images.

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 WebAssembly container images in Kubernetes​

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'.

A simple WebAssembly app​

A separate article explains how to compile, package, and publish a simple WebAssembly WASI program 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 run -it --rm --restart=Never wasi-demo --image=wasmedge/example-wasi:latest --annotations="module.wasm.image/variant=compat-smart" --overrides='{"kind":"Pod", "apiVersion":"v1", "spec": {"hostNetwork": true}}' /wasi_example_main.wasm 50000000

The output from the containerized application is printed into the console.

Random number: 401583443
Random bytes: [192, 226, 162, 92, 129, 17, 186, 164, 239, 84, 98, 255, 209, 79, 51, 227, 103, 83, 253, 31, 78, 239, 33, 218, 68, 208, 91, 56, 37, 200, 32, 12, 106, 101, 241, 78, 161, 16, 240, 158, 42, 24, 29, 121, 78, 19, 157, 185, 32, 162, 95, 214, 175, 46, 170, 100, 212, 33, 27, 190, 139, 121, 121, 222, 230, 125, 251, 21, 210, 246, 215, 127, 176, 224, 38, 184, 201, 74, 76, 133, 233, 129, 48, 239, 106, 164, 190, 29, 118, 71, 79, 203, 92, 71, 68, 96, 33, 240, 228, 62, 45, 196, 149, 21, 23, 143, 169, 163, 136, 206, 214, 244, 26, 194, 25, 101, 8, 236, 247, 5, 164, 117, 40, 220, 52, 217, 92, 179]
Printed from wasi: This is from a main function
This is from a main function
The env vars are as follows.
The args are as follows.
/wasi_example_main.wasm
50000000
File content is This is in a file
pod "wasi-demo-2" deleted

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 run --restart=Never http-server --image=wasmedge/example-wasi-http:latest --annotations="module.wasm.image/variant=compat-smart" --overrides='{"kind":"Pod", "apiVersion":"v1", "spec": {"hostNetwork": true}}'

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!