创建application
针对业务开发人员来讲：应用分为前端、后端、（定时）任务。
对于kubernetes操作人员来讲，我不管你们什么前端、后端，都是deployment/pods、statefuset、job或是cronjob。从这个角度，其实并不清楚应用间的调用关系，并不明朗，这个是oam要解决的问题。
部署一个应用：
kubectl apply -f - <<EOF
apiVersion: core.oam.dev/v1beta1
kind: Application
metadata:
name: example-app
annotations:
app.oam.dev/revision-only: "true"
spec:
components:
- name: testsvc
type: webservice
properties:
addRevisionLabel: true
image: crccheck/hello-world
port: 8000
EOF
部署完后，发现其实并没有pods
$ k get po
No resources found in default namespace.
原因是使用了annotation: app.oam.dev/revision-only: "true"
这个annotation是定义资源被appdeploymnet控制
可以看到已经有apprev
➜ ~ kubectl get apprev
NAME AGE
example-app-v1 2m12s
创建appdeployment
kubectl apply -f - <<EOF
apiVersion: core.oam.dev/v1beta1
kind: AppDeployment
metadata:
name: example-appdeploy
spec:
appRevisions:
- revisionName: example-app-v1
placement:
- distribution:
replicas: 2
EOF
应用appdeployment后，可以看到负载已经正确创建，且deployment有两个副本
k get deploy
NAME READY UP-TO-DATE AVAILABLE AGE
testsvc-v1 2/2 2 2 91s
k get po
NAME READY STATUS RESTARTS AGE
testsvc-v1-5c94ff8db7-6tx5n 1/1 Running 0 94s
testsvc-v1-5c94ff8db7-dw558 1/1 Running 0 94s
更新application
应用名一样，镜像由hello-world变为nginx
cat <<EOF | kubectl apply -f -
apiVersion: core.oam.dev/v1beta1
kind: Application
metadata:
name: example-app
annotations:
app.oam.dev/revision-only: "true"
spec:
components:
- name: testsvc
type: webservice
properties:
addRevisionLabel: true
image: nginx
port: 80
EOF
更新完后，会有两个版本
$ kubectl get apprev
NAME AGE
example-app-v1 9m58s
example-app-v2 13s
虽然application的revision更新了，但是pods仍旧没有变化。
原因是owner不是application，而是appdeployment
$ kubectl get deploy -oyaml |grep -i owner -C 2
...
blockOwnerDeletion: true
controller: true
kind: AppDeployment
而appdeployment中定义的还是version v1
# k get appdeployment example-appdeploy -oyaml
...
spec:
appRevisions:
- placement:
- distribution:
replicas: 2
revisionName: example-app-v1
更新appdeployment实现分流
分流的功能本质上是借助于istio 的能力，但是屏蔽了istio的复杂配置。
安装istio
istioctl install --demo
等待安装成功：
➜ kubectl get po -n istio-system
NAME READY STATUS RESTARTS AGE
istio-egressgateway-bd477794-md2n6 1/1 Running 0 4h3m
istio-ingressgateway-79df7c789f-pbw2v 1/1 Running 0 4h3m
istiod-6dc55bbdd-fv859 1/1 Running 0 4h5m
部署appdeployment，安流量比例分
apply gateway
kubectl apply -f - <<EOF
apiVersion: networking.istio.io/v1alpha3
kind: Gateway
metadata:
name: example-app-gateway
spec:
selector:
istio: ingressgateway # use istio default controller
servers:
- port:
number: 80
name: http
protocol: HTTP
hosts:
- "*"
EOF
检查gateway成功创建
kubectl get gateway
NAME AGE
example-app-gateway 4h12m
更新appdeployment
kubectl apply -f - <<EOF
apiVersion: core.oam.dev/v1beta1
kind: AppDeployment
metadata:
name: example-appdeploy
spec:
traffic:
hosts:
- example-app.example.com
gateways:
- example-app-gateway
http:
- weightedTargets:
- revisionName: example-app-v1
componentName: testsvc
port: 8000
weight: 50
- revisionName: example-app-v2
componentName: testsvc
port: 80
weight: 50
appRevisions:
- revisionName: example-app-v1
placement:
- distribution:
replicas: 1
- revisionName: example-app-v2
placement:
- distribution:
replicas: 1
EOF
检查deployment成功创建
kubectl get deploy
NAME READY UP-TO-DATE AVAILABLE AGE
testsvc-v1 1/1 1 1 35m
testsvc-v2 1/1 1 1 23m
验证
把istio ingress gateway svc暴露，让外网访问
kubectl -n istio-system port-forward service/istio-ingressgateway 8080:80
Forwarding from 127.0.0.1:8080 -> 8080
Forwarding from [::1]:8080 -> 8080
访问：
➜ ~ curl -H "Host: example-app.example.com" http://localhost:8080/
<!DOCTYPE html>
<html>
<head>
<title>Welcome to nginx!</title>
<style>
再次访问：
➜ ~ curl -H "Host: example-app.example.com" http://localhost:8080/
<xmp>
Hello World
## .
## ## ## ==
## ## ## ## ## ===
/""""""""""""""""\___/ ===
~~~ {~~ ~~~~ ~~~ ~~~~ ~~ ~ / ===- ~~~
\______ o _,/
\ \ _,'
`'--.._\..--''
</xmp>
依次访问，会发现交叉出现两个页面，证明分流成功。
总结：
这个流程总结为：
- 创建app，指定使用appdeployment控制；
- 更新app，生成两个版本v1,v2；
- 更新appdeployment，指定两个版本的流量比例；
疑问1：在app中不能一下次定义两个版本吗？
疑问2：这个分流是使用istio的功能吗 是的，使用的是istio的virtualservice，如：
➜ ~ k get virtualservice
NAME GATEWAYS HOSTS AGE
example-appdeploy ["example-app-gateway"] ["example-app.example.com"] 18m