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Run WASM applications from Kubernetes

Yingting Huang

• 4 min read
Run WASM applications from Kubernetes
  • Interested in running WASM workload from Kubernetes?
  • Interested in turning your Kubernetes cluster to support multiple container shims?
  • Even more, wasm with dapr support?

The steps documented here help run WASM workload from Kubernetes cluster based on great work from

Sample applications and deploy manifests are located at this repo

Below are pre-requisite

  • A Kubernetes cluster, node can be accessed directly to install shims and configure containerd. For managed Kubernetes cluster, a potential workaround is using daemonset to install shim and configure containerd. Some Kubernetes distribution, for example AKS already provided preview feature to enable WASM support

WasmEdge Containerd Crun Shims

WasmEdge containerd shim is based on crun project, to bake WasmEdge runtime into crun, we need to add WasmEdge to Kubernetes cluster and build crun with WasmEdge support manully.

Install WasmEdge

Install WasmEdge to Kubernetes node

curl -sSf https://raw.githubusercontent.com/WasmEdge/WasmEdge/master/utils/install.sh | sudo bash -s -- -p /usr/local

Build crun with WasmEdge support

Install building tools and libraries

sudo apt update
sudo apt install -y make git gcc build-essential pkgconf libtool \
    libsystemd-dev libprotobuf-c-dev libcap-dev libseccomp-dev libyajl-dev \
    go-md2man libtool autoconf python3 automake

Next, configure, build, and install a crun binary with WasmEdge support.

git clone https://github.com/containers/crun
cd crun
./autogen.sh
./configure --with-wasmedge
make
sudo make install

Maps the runtime type to the shim binary

vi /etc/containerd/config.toml

        [plugins."io.containerd.grpc.v1.cri".containerd.runtimes.crun]
          runtime_type = "io.containerd.runc.v2"
          privileged_without_host_devices = false
          pod_annotations = ["*.wasm.*", "wasm.*", "module.wasm.image/*", "*.module.wasm.image", "module.wasm.image/variant.*"]
          [plugins."io.containerd.grpc.v1.cri".containerd.runtimes.crun.options]
            BinaryName = "crun"

systemctl restart containerd
systemctl status containerd

Add a RuntimeClass to support WasmEdge crun containerd shim from Kubernetes cluster

# wasmedge-crun-v2.yaml
apiVersion: node.k8s.io/v1
handler: crun
kind: RuntimeClass
metadata:
  name: wasmedge-crun
scheduling:
  nodeSelector:
    kubernetes.azure.com/wasmedge-crun: "true"

Add label to Kubernetes nodes, mark them to support WasmEdge workload

kubectl apply -f wasmedge-crun.yaml
kubectl label nodes <NODE> kubernetes.azure.com/wasmedge-crun=true

Deploy sample WASM application

kubectl apply -f https://raw.githubusercontent.com/huangyingting/wasm/main/deploy/rust-wasmedge.yaml

Test WASM application, open two terminal windows, from first terminal window, run

kubectl port-forward svc/rust-wasmedge 8080:80

From second terminal window, run below command and notice the request is echoed back

curl http://localhost:8080

# HTTP response by WASM echo application
:method: GET
Host: localhost:8080
User-Agent: curl/7.81.0
Accept: */*

Deis Labs Containerd Wasm Shims

Deis Labs provided two great containerd shims

Install Deis Labs Containerd Wasm Shims

Using a shim in Kubernetes has brief steps to install deis lab containerd wasm shims

Here are more detailed steps

Install containerd shims to Kubernetes node

RELEASE=v0.9.1
wget -qO- https://github.com/deislabs/containerd-wasm-shims/releases/download/$RELEASE/containerd-wasm-shims-v1-slight-linux-x86_64.tar.gz | sudo tar -xvz -C /usr/local/bin
wget -qO- https://github.com/deislabs/containerd-wasm-shims/releases/download/$RELEASE/containerd-wasm-shims-v1-spin-linux-x86_64.tar.gz | sudo tar -xvz -C /usr/local/bin

Add the following to the containerd /etc/containerd/config.toml (The default configuration can be generated by running containerd config default) that maps the runtime type to the shim binary,

vi /etc/containerd/config.toml

        [plugins."io.containerd.grpc.v1.cri".containerd.runtimes.spin]
          runtime_type = "io.containerd.spin.v1"
        [plugins."io.containerd.grpc.v1.cri".containerd.runtimes.slight]
          runtime_type = "io.containerd.slight.v1"

systemctl restart containerd
systemctl status containerd

Add RuntimeClass to support spin & slight from Kubernetes cluster

# runtimeclass.yaml
apiVersion: node.k8s.io/v1
handler: slight
kind: RuntimeClass
metadata:
  name: wasmtime-slight
scheduling:
  nodeSelector:
    kubernetes.azure.com/wasmtime-slight: "true"
---
apiVersion: node.k8s.io/v1
handler: spin
kind: RuntimeClass
metadata:
  name: wasmtime-spin
scheduling:
  nodeSelector:
    kubernetes.azure.com/wasmtime-spin: "true"

Label Kubernetes nodes to support spin & slight workload

kubectl apply -f runtimeclass.yaml
kubectl label nodes <NODE> kubernetes.azure.com/wasmtime-slight=true
kubectl label nodes <NODE> kubernetes.azure.com/wasmtime-spin=true

Deploy sample WASM application

kubectl apply -f https://raw.githubusercontent.com/huangyingting/wasm/main/deploy/go-spin.yaml

Test WASM application, open two terminal windows, from first terminal window, run

kubectl port-forward svc/go-spin 8080:80

From second terminal window, run below command and notice the request is echoed back

curl http://localhost:8080

# HTTP response by WASM echo application
GET / HTTP/1.1
Host: localhost:8080
Accept: */*
Spin-Base-Path: /
Spin-Component-Route: 
Spin-Full-Url: http://localhost:8080/
Spin-Matched-Route: /...
Spin-Path-Info: /
Spin-Raw-Component-Route: /...
User-Agent: curl/7.81.0


arch: wasm
os: linux
version: v0.1.0

Sample applications

This repo also provides a few of sample applications to run WASM applications from Kubernetes cluster

  • dotnet-spin, a simple WASM http echo server written on c# language
  • go-spin, a simple WASM http echo server written on golang language
  • rust-wasmedge, a simple WASM http echo server written on rust language

Build and deploy

This repo has github action workflows to build and push images to ghcr.io. Check .github/workflows/build-spin-images.yaml and .github/workflows/build-wasmedge-images.yaml for how those WASM container images are built.

deploy directory has all the Kubernetes manifests to deploy sample applications.

To run applications locally, it requires

  • Rust
  • .NET 7.0 SDK
  • Go
  • TinyGo
  • spin
  • WasmEdge
    To run spin application, change directory to go-spin or dotnet-spin, run spin build and spin up
    To run WasmEdge application, change directory to rust-wasmedge, run
rustup target add wasm32-wasi
cargo build --release --target wasm32-wasi
wasmedge target/wasm32-wasi/release/rust-wasmedge.wasm

rust-wasmedge also supports dapr, to add dapr sidecar, add below annotations to deploy/rust-wasmedge.yaml

...
      annotations:
        module.wasm.image/variant: compat-smart
        # Dapr support
        dapr.io/enabled: "true"
        dapr.io/app-id: "rust-wasmedge"
        dapr.io/app-port: "80"

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