介绍

Krustlet 是基于k8s运行wasm程序的负载，通过亲和性来运行wasm程序，其实现了kubelet api，且兼容了 kubectl logs 和 kubectl delete 命令。

接下来将一步步安装、运行krustlet

kind安装

kind config配置

kind: Cluster
apiVersion: kind.sigs.k8s.io/v1alpha3
kubeadmConfigPatches:
- |
  apiVersion: kubeadm.k8s.io/v1beta1
  kind: ClusterConfiguration
  metadata:
    name: config
  networking:
    serviceSubnet: 10.0.0.0/16
  imageRepository: registry.aliyuncs.com/google_containers
  nodeRegistration:
    kubeletExtraArgs:
      pod-infra-container-image: registry.aliyuncs.com/google_containers/pause:3.1
- |
  apiVersion: kubeadm.k8s.io/v1beta1
  kind: InitConfiguration
  metadata:
    name: config
  networking:
    serviceSubnet: 10.0.0.0/16
  imageRepository: registry.aliyuncs.com/google_containers
nodes:
- role: control-plane
- role: worker
- role: worker

创建集群

kind create --config=kind-config.yaml

运行krustlet

生成kubeconfig

通过脚本生成bootstrap config

bash <(curl https://raw.githubusercontent.com/deislabs/krustlet/master/docs/howto/assets/bootstrap.sh)

krustlet安装

wget https://krustlet.blob.core.windows.net/releases/krustlet-v0.3.0-macos-amd64.tar.gz
tar xf krustlet-v0.3.0-macos-amd64.tar.gz
chmod +x krustlet-*
mv krustlet-* /usr/local/bin/

启动krustlet

/usr/local/bin/krustlet-wasi  --node-ip 192.168.11.5 --bootstrap-file=~/.krustlet/config/bootstrap.conf

approve 证书

像kubelet一样，通过bootstrap config启动后会发起一个csr,我们需要对其approve

kubectl certificate approve  Mbp.local-tls

查看状态

可以看到已经处于ready状态

kubectl get nodes
NAME                 STATUS   ROLES    AGE   VERSION
kind-control-plane   Ready    master   16m   v1.18.2
kind-worker          Ready    <none>   15m   v1.18.2
kind-worker2         Ready    <none>   15m   v1.18.2
mbp.local            Ready    agent    9s    0.3.0

查看污点

kubectl get nodes mbp.local -o json | jq .spec.taints
[
  {
    "effect": "NoExecute",
    "key": "krustlet/arch",
    "value": "wasm32-wasi"
  }
]

krustlet运行wasi

下载wasm-to-oci

我们需要下载wasm-to-oci工具，使用该工具可以将wasm程序推送到docker仓库。

wget https://github.com/engineerd/wasm-to-oci/releases/download/v0.1.1/darwin-amd64-wasm-to-oci

生成wasi程序

创建项目

cargo new krust-test

代码如下

#[no_mangle]
fn _start() {
    let mut i:i32 = 0;
    loop {
        println!("hello {:?}",i);
        i+=1;
        sleep(Duration::new(1, 0))
    }
}

编译

cargo build --target=wasm32-wasi

准备一个oci v2registry

支持以下几种registry

• Distribution (open source, version 2.7+)
• Azure Container Registry
• Google Container Registry
• Harbor Container Registry v2.0

这里我自行搭建了一个，证书通过letsencrypt生成

docker run   -v /media:/certs \
>   -e REGISTRY_HTTP_ADDR=0.0.0.0:443 \
>   -e REGISTRY_HTTP_TLS_CERTIFICATE=/certs/fullchain.crt \
>   -e REGISTRY_HTTP_TLS_KEY=private.pem \
>   -p 443:443 \
>   registry:2

将编译好的wasm文件推送到仓库

wasm-to-oci push .//target/wasm32-wasi/release/krustlet_test.wasm reg.rocdu.top/test/krustlet:v1

运行wasi wavm程序

我们将运行一个wasm pod,通过容忍策略让该pod可以运行在我们的krustlet节点上面

apiVersion: v1
kind: Pod
metadata:
  name: krustlet-tutorial
spec:
  containers:
    - name: krustlet-tutorial
      image: reg.rocdu.top/test/krustlet:v1
  tolerations:
    - key: "krustlet/arch"
      operator: "Equal"
      value: "wasm32-wasi"
      effect: "NoExecute"

查看运行状态，可以看到已经处于运行状态，让我们看一下日志的输出，可以看到是我们预期的输出。

kubectl get pods -w
NAME                READY   STATUS    RESTARTS   AGE
krustlet-tutorial   0/1     Pending   0          14s
krustlet-tutorial   0/1     Running   0          14s


kubectl logs krustlet-tutorial -f
hello 1
hello 2
hello 3

总结

krustlet以及wasi都是很不成熟的项目，仅限用于测试。

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