knative helloworld

像学习任何一门编程语言一样,先不管实现原理,基础架构.先跑起来一个helloworld,helloworld跑通之后,获的一点点成就感和一个总体的认识之后再研究基础的东西.认识knative也是如此,先把knative的helloworld 跑通之后再深揪基本原理.

install knative

安装knative之前必须安装好istio,关于istio的安装请参考前面的介绍.

1. 安装knative

kubectl apply --selector knative.dev/crd-install=true \
--filename https://github.com/knative/serving/releases/download/v0.10.0/serving.yaml \
--filename https://github.com/knative/eventing/releases/download/v0.8.1/release.yaml \
--filename https://github.com/knative/serving/releases/download/v0.10.0/monitoring.yaml

kubectl apply  \
--filename https://github.com/knative/serving/releases/download/v0.10.0/serving.yaml \
--filename https://github.com/knative/eventing/releases/download/v0.8.1/release.yaml \
--filename https://github.com/knative/serving/releases/download/v0.10.0/monitoring.yaml

2. 替换gcr.io 镜像

由于gcr.io被gfw墙了,很多gcr.io的镜像国内拉不下来.可以使用gcr.azk8s.cn来替换

 kubectl get deployment webhook  -n knative-serving -o yaml >test.yaml && sed  "s#gcr.io#gcr.azk8s.cn#g" test.yaml  >test-new.yaml && kubectl replace -f test-new.yaml   

部署第一个helloworld

cat <<EOF > knative-helloworld.yaml
apiVersion: serving.knative.dev/v1 # Current version of Knative
kind: Service
metadata:
  name: helloworld-go # The name of the app
  namespace: default # The namespace the app will use
spec:
  template:
    spec:
      containers:
        - image: gcr.azk8s.cn/knative-samples/helloworld-go # The URL to the image of the app
          env:
            - name: TARGET # The environment variable printed out by the sample app
              value: "Go Sample v1"
EOF

kubectl create -f knative-helloworld.yaml

➜  ~ kubectl get ksvc
NAME            URL                                        LATESTCREATED         LATESTREADY           READY   REASON
helloworld-go   http://helloworld-go.default.example.com   helloworld-go-c2drn   helloworld-go-c2drn   True

至次我们通过上面的yaml文件向k8s提交了一个knative 自定义的crd,services.serving.knative.dev.

kubectl get services.serving.knative.dev
NAME            URL                                        LATESTCREATED         LATESTREADY           READY   REASON
helloworld-go   http://helloworld-go.default.example.com   helloworld-go-c2drn   helloworld-go-c2drn   True

上面的ksvc是services.serving.knative.dev的简写.

访问 hello-world

部署第一个knative hello-word后怎么访问呢,上面的svc的信息显示一个域名 helloworld-go.default.example.com 我们通过这个域名可以访问到 hello-world-go 应用.

export INGRESS_HOST=10.1.1.1
export INGRESS_PORT=31380
curl -I -HHost:helloworld-go.default.example.com http://$INGRESS_HOST:$INGRESS_PORT

上面的INGRESS_HOST是istio-ingressgateway服务的监听ip地址,INGRESS_PORT是端口,因为我的istio-ingressgateway是node—port类型.开始的时候说安装knative需要istio这就是其中一个原因,knative 通过istio-ingressgateway暴露它的服务.具体的实现后面的文章会分析.

[root@host~]# curl -I -HHost:helloworld-go.default.example.com http://$INGRESS_HOST:$INGRESS_PORT
HTTP/1.1 200 OK
content-length: 20
content-type: text/plain; charset=utf-8
date: Thu, 28 Nov 2019 10:11:31 GMT
x-envoy-upstream-service-time: 3309
server: istio-envoy

[root@host108752172 ~]# kubectl get  pods
NAME                                              READY   STATUS    RESTARTS   AGE
helloworld-go-c2drn-deployment-5ccc555d74-g6spw   2/2     Running   0          11s
nginx-deployment-basic-5754944d6c-rg7vk           1/1     Running   0          2d22h
prometheus-persisted-0                            0/3     Pending   0          13d

curl hello-world-go 服务的时候稍微有点延迟,是因为没有request进来 helloworld-go 被auto-scaler为0. 需要拉起这个pod.

总结

一个简单的knative的应用跑起来了,可能会有疑惑,knative到底和传统的k8s上的web应用有啥不同,knative部署完了在k8s上到底增加了什么东西，这些下篇文章继续分析.