SuperEdge: Extending edge computing scenarios with WebAssembly

author

SuperEdge Developer Team

summary

SuperEdge is an open source distributed edge computing container management system for , which is used to manage computing resources and container applications in multiple cloud edge regions. In the current architecture, these resources and applications can be managed as a Kubernetes-native resource.

In some cases, however, edge devices often require some lighter-weight, better-performing runtimes. It is also necessary to reduce container images in GB, and increase the startup time of containers to seconds or even milliseconds, and WebAssembly based on the virtual machine stack binary instruction format can better handle this situation.

WasmEdge is a lightweight, high-performance, and scalable WebAssembly runtime for cloud-native, edge, and decentralized applications. It is the fastest growing Wasm runtime today and has a very active community.

Running diagram

Superedge recently supported Containerd, and at the edge we will have Containerd use crun to support the WasmEdge runtime. That is, after following these steps, your edge nodes can support both OCI containers and WASM containers.

Install SuperEdge edge K8s cluster

• Download the installation package

arch=amd64 version=v0.7.0 && rm -rf edgeadm-linux-* && wget https://superedge-1253687700.cos.ap-guangzhou.myqcloud.com/$version/$arch/edgeadm-linux-containerd-$arch-$version.tgz && tar -xzvf edgeadm-linux-* && cd edgeadm-linux-$arch-$version && ./edgeadm

Pay attention to select the installation package corresponding to the machine architecture. This installation package has the Containerd container runtime by default.

• Create an edge cluster

./edgeadm init --kubernetes-version=1.18.2 --image-repository superedge.tencentcloudcr.com/superedge --service-cidr=10.96.0.0/12 --pod-network-cidr=192.168.0.0/16 --install-pkg-path ./kube-linux-*.tar.gz --apiserver-cert-extra-sans=<Master Public IP> --apiserver-advertise-address=<Master Intranet IP> --enable-edge=true --runtime=containerd

Note that with the parameter --runtime=containerd , it means using the containerd container runtime, and --runtime=dockerd means using the Docker container runtime.

• Join edge nodes

./edgeadm join <Master Public/Intranet IP Or Domain>:Port --token xxxx --discovery-token-ca-cert-hash sha256:xxxxxxxxxx --install-pkg-path ./kube-linux-*.tar.gz --enable-edge=true --runtime=containerd

For details, see SuperEdge official document One-click installation of native k8s cluster and edge K8s cluster

Install the WasmEdge runtime environment

Install WasmEdge

WasmEdge can be easily installed using a script on the edge node. Execute the following script on the edge node:

curl -sSf https://raw.githubusercontent.com/WasmEdge/WasmEdge/master/utils/install.sh | bash

install crunch

crun The project has built-in WasmEdge support, but the default crun release does not compile the wasmedge module. Currently, it is necessary to manually build the crun binary that supports WasmEdge from the source code.
First, make sure the crun dependencies are installed on your Ubuntu 20.04. For other Linux distributions see crun's README .

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, compile and install crun:

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

Configure Containerd to use the crun runtime

Here we give the difference between the original configuration and the configuration of the containerd file /etc/containerd/config.toml that needs to be configured. Users can modify it according to the comparison.

cat > config.toml.diff << EOF
--- /etc/containerd/config.toml 2022-02-14 15:05:40.061562127 +0800
+++ /etc/containerd/config.toml.crun    2022-02-14 15:03:35.846052853 +0800
@@ -24,17 +24,23 @@
   max_concurrent_downloads = 10

   [plugins.cri.containerd]
-        default_runtime_name = "runc"
-    [plugins.cri.containerd.runtimes.runc]
+        default_runtime_name = "crun"
+    [plugins.cri.containerd.runtimes.crun]
       runtime_type = "io.containerd.runc.v2"
-      pod_annotations = []
+      pod_annotations = ["*.wasm.*", "wasm.*", "module.wasm.image/*", "*.module.wasm.image", "module.wasm.image/variant.*"]
       container_annotations = []
       privileged_without_host_devices = false
-      [plugins.cri.containerd.runtimes.runc.options]
-        BinaryName = "runc"
+      [plugins.cri.containerd.runtimes.crun.options]
+        BinaryName = "crun"
   # cni
   [plugins.cri.cni]
     bin_dir = "/opt/cni/bin"
     conf_dir = "/etc/cni/net.d"
     conf_template = ""

+  [plugins."io.containerd.runtime.v1.linux"]
+    no_shim = false
+    runtime = "crun"
+    runtime_root = ""
+    shim = "containerd-shim"
+    shim_debug = false
EOF

Finally restart the containerd container runtime

sudo patch -d/ -p0 < config.toml.diff
sudo systemctl restart containerd

Create a WASM application

We will use a wasm example image wasm-wasi-example 1623853b18bd88 already on . Here, the wasm image needs to add an Annotation of "module.wasm.image/variant":"compat" to the image's Manfest file so that the runtime can distinguish between the wasm and the operating system, so the docker build function cannot be satisfied, you can use buildah to build the wasm image and push it to any OCI standard mirror repository.

cat > wasmedge-app.yaml << EOF
apiVersion: v1
kind: Pod
metadata:
  annotations:
    module.wasm.image/variant: compat
  labels:
    run: wasi-demo
  name: wasi-demo
spec:
  containers:
  - args:
    - /wasi_example_main.wasm
    - "50000000"
    image: hydai/wasm-wasi-example:with-wasm-annotation
    imagePullPolicy: IfNotPresent
    name: wasi-demo
  hostNetwork: true
  restartPolicy: Never
EOF

kubectl create -f wasmedge-app.yaml

Use kubectl logs wasi-demo to see the output of this program as follows:

Random number: -1643170076
Random bytes: [15, 223, ... 106, 51]
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

future

With more extensive edge device access and more edge scenario coverage requirements, SuperEdge not only supports traditional docker and containerd in edge computing runtime, but also supports various WebAssembly runtimes (WasmEdge), and will continue to Create an imaginative and infinitely possible edge computing and scheduling platform for developers.

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