knative（个人笔记）

Posted on Edited on

理论

待补充

安装

下载kind命令，但不需要创建一个k8s集群。

执行如下命令下载kn 二进制文件

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wget https://github.com/knative/client/releases/download/knative-v1.2.0/kn-linux-amd64
mv kn-linux-amd64 /usr/local/bin/kn
chmod +x /usr/local/bin/kn 

# 自动补全
echo -e "\n# kn" >> ~/.bash_profile
echo 'source <(kn completion bash)' >>~/.bash_profile

下载quickstart二进制文件

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wget https://github.com/knative-sandbox/kn-plugin-quickstart/releases/download/knative-v1.2.0/kn-quickstart-linux-amd64
mv kn-quickstart-linux-amd64 /usr/local/bin/kn-quickstart
chmod +x /usr/local/bin/kn-quickstart 

# 如下两条命令可以得到相同的输出结果
kn quickstart --help
kn-quickstart --help

执行 kn quickstart kind 命令即可创建出一个knative的k8s集群。

knative serving

serving的核心功能为提供弹性扩缩容能力。

CRD

image.png
Service：用来管理整个应用的生命周期。
Route：用来将流量分发到不同的Revision
Configuration：
Revision：

kpa功能

实践

最简单service

创建hello.yaml文件，内容如下，并执行 kubectl apply -f hello.yaml。其中service的名字为hello，revision的名字为world。

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apiVersion: serving.knative.dev/v1
kind: Service
metadata:
  name: hello
spec:
  template:
    metadata:
      # This is the name of our new "Revision," it must follow the convention {service-name}-{revision-name}
      name: hello-world
    spec:
      containers:
        - image: gcr.io/knative-samples/helloworld-go
          ports:
            - containerPort: 8080
          env:
            - name: TARGET
              value: "World"

通过kn命令可以看到创建了一个service hello，并且有一个可以访问的url地址。

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# kn service list
NAME    URL                                       LATEST        AGE    CONDITIONS   READY   REASON
hello   http://hello.default.127.0.0.1.sslip.io   hello-world   154m   3 OK / 3     True

knative抽象了Revision来标识该service对应的版本信息，可以使用kubectl命令，也可以使用kn命令来查看revision信息。

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$ k get revisions.serving.knative.dev 
NAME          CONFIG NAME   K8S SERVICE NAME   GENERATION   READY   REASON   ACTUAL REPLICAS   DESIRED REPLICAS
hello-world   hello                            1            True             0                 0
$ kn revision list
NAME          SERVICE   TRAFFIC   TAGS   GENERATION   AGE     CONDITIONS   READY   REASON
hello-world   hello     100%             1            6m33s   3 OK / 4     True

在宿主机上执行 curl http://hello.default.127.0.0.1.sslip.io 接口访问刚才创建的service。这里比较有意思的是为什么域名可以在宿主机上解析，该域名实际上是通过公网来解析的，域名服务器sslip.io负责该域名的解析。
本机的127.0.0.1的80端口实际是指向的是kind容器的31080端口，而31080为kourier-ingress对外暴露的服务。

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# kubectl  get svc -A | grep 31080
kourier-system     kourier-ingress   NodePort       10.96.252.144   <none>    80:31080/TCP     3h16m

kourier-ingress为knative使用的ingress服务，该ingress并非k8s原生的ingress对象，而是自定义的ingress networking.internal.knative.dev/v1alpha1。service hello在创建的时候会同步创建一个ingress对象。在该ingress对象中可以看到刚才访问的域名hello.default.127.0.0.1.sslip.io，同时可以看到该ingress将域名指向到了k8s的service hello-world.default。

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kubectl  get  ingresses.networking.internal.knative.dev hello -o yaml 
apiVersion: networking.internal.knative.dev/v1alpha1
kind: Ingress
metadata:
  annotations:
    networking.internal.knative.dev/rollout: '{"configurations":[{"configurationName":"hello","percent":100,"revisions":[{"revisionName":"hello-world","percent":100}],"stepParams":{}}]}'
    networking.knative.dev/ingress.class: kourier.ingress.networking.knative.dev
    serving.knative.dev/creator: kubernetes-admin
    serving.knative.dev/lastModifier: kubernetes-admin
  finalizers:
  - ingresses.networking.internal.knative.dev
  generation: 1
  labels:
    serving.knative.dev/route: hello
    serving.knative.dev/routeNamespace: default
    serving.knative.dev/service: hello
  name: hello
  namespace: default
  ownerReferences:
  - apiVersion: serving.knative.dev/v1
    blockOwnerDeletion: true
    controller: true
    kind: Route
    name: hello
    uid: 4c58e77b-4871-42cc-bfa0-aa9fda9646ed
spec:
  httpOption: Enabled
  rules:
  - hosts:
    - hello.default
    - hello.default.svc
    - hello.default.svc.cluster.local
    http:
      paths:
      - splits:
        - appendHeaders:
            Knative-Serving-Namespace: default
            Knative-Serving-Revision: hello-world
          percent: 100
          serviceName: hello-world
          serviceNamespace: default
          servicePort: 80
    visibility: ClusterLocal
  - hosts:
    - hello.default.127.0.0.1.sslip.io
    http:
      paths:
      - splits:
        - appendHeaders:
            Knative-Serving-Namespace: default
            Knative-Serving-Revision: hello-world
          percent: 100
          serviceName: hello-world
          serviceNamespace: default
          servicePort: 80
    visibility: ExternalIP
status:
  conditions:
  - lastTransitionTime: "2022-03-11T12:47:26Z"
    status: "True"
    type: LoadBalancerReady
  - lastTransitionTime: "2022-03-11T12:47:26Z"
    status: "True"
    type: NetworkConfigured
  - lastTransitionTime: "2022-03-11T12:47:26Z"
    status: "True"
    type: Ready
  observedGeneration: 1
  privateLoadBalancer:
    ingress:
    - domainInternal: kourier-internal.kourier-system.svc.cluster.local
  publicLoadBalancer:
    ingress:
    - domainInternal: kourier.kourier-system.svc.cluster.local

在default namespace下可以看到有三个service，其中hello-world的ingress转发的service。

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# k get svc | grep hello
hello                                   ExternalName   <none>         kourier-internal.kourier-system.svc.cluster.local   80/TCP                                       155m
hello-world                             ClusterIP      10.96.58.149   <none>                                              80/TCP                                       155m
hello-world-private                     ClusterIP      10.96.54.163   <none>                                              80/TCP,9090/TCP,9091/TCP,8022/TCP,8012/TCP   155m

通过查看该serivce的yaml，并未定义serivce的selector。

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apiVersion: v1
kind: Service
metadata:
  annotations:
    autoscaling.knative.dev/class: kpa.autoscaling.knative.dev
    serving.knative.dev/creator: kubernetes-admin
  labels:
    app: hello-world
    networking.internal.knative.dev/serverlessservice: hello-world
    networking.internal.knative.dev/serviceType: Public
    serving.knative.dev/configuration: hello
    serving.knative.dev/configurationGeneration: "1"
    serving.knative.dev/configurationUID: 13138d0f-ee5f-4631-94a5-6928546e504c
    serving.knative.dev/revision: hello-world
    serving.knative.dev/revisionUID: f3aaae74-6b79-4785-b60d-5607c0ab3bcf
    serving.knative.dev/service: hello
    serving.knative.dev/serviceUID: 79907029-32df-4f21-b14b-ed7d24e1a10e
  name: hello-world
  namespace: default
  ownerReferences:
  - apiVersion: networking.internal.knative.dev/v1alpha1
    blockOwnerDeletion: true
    controller: true
    kind: ServerlessService
    name: hello-world
    uid: 3a6326c5-32b0-4074-bec2-4d3eed293b71
spec:
  clusterIP: 10.96.58.149
  clusterIPs:
  - 10.96.58.149
  internalTrafficPolicy: Cluster
  ipFamilies:
  - IPv4
  ipFamilyPolicy: SingleStack
  ports:
  - name: http
    port: 80
    protocol: TCP
    targetPort: 8012
  sessionAffinity: None
  type: ClusterIP
status:
  loadBalancer: {}

查看Service对应的Endpoint对象，可以看到Endpoint对象实际上指向到了knative-serving下的pod activator-85bd4ddcbb-6ms7n。

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apiVersion: v1
kind: Endpoints
metadata:
  annotations:
    autoscaling.knative.dev/class: kpa.autoscaling.knative.dev
    serving.knative.dev/creator: kubernetes-admin
  labels:
    app: hello-world
    networking.internal.knative.dev/serverlessservice: hello-world
    networking.internal.knative.dev/serviceType: Public
    serving.knative.dev/configuration: hello
    serving.knative.dev/configurationGeneration: "1"
    serving.knative.dev/configurationUID: 13138d0f-ee5f-4631-94a5-6928546e504c
    serving.knative.dev/revision: hello-world
    serving.knative.dev/revisionUID: f3aaae74-6b79-4785-b60d-5607c0ab3bcf
    serving.knative.dev/service: hello
    serving.knative.dev/serviceUID: 79907029-32df-4f21-b14b-ed7d24e1a10e
  name: hello-world
  namespace: default
  ownerReferences:
  - apiVersion: networking.internal.knative.dev/v1alpha1
    blockOwnerDeletion: true
    controller: true
    kind: ServerlessService
    name: hello-world
    uid: 3a6326c5-32b0-4074-bec2-4d3eed293b71
subsets:
- addresses:
  - ip: 10.244.0.5
    nodeName: knative-control-plane
    targetRef:
      kind: Pod
      name: activator-85bd4ddcbb-6ms7n
      namespace: knative-serving
      resourceVersion: "809"
      uid: df916ac6-3161-4bc6-bf8c-47bb7c83cc4a
  ports:
  - name: http
    port: 8012
    protocol: TCP

进一步查看knative-serving下有一个knative的组件activator。

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k get deploy -n knative-serving activator 
NAME        READY   UP-TO-DATE   AVAILABLE   AGE
activator   1/1     1            1           3h35m

打开终端，执行一下 kubectl get pod -l serving.knative.dev/service=hello -w，重新执行 curl http://hello.default.127.0.0.1.sslip.io 发起新的请求，可以看到会有pod产生，且pod为通过deployment拉起。

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$ kubectl get pod -l serving.knative.dev/service=hello -w
hello-world-deployment-7ff4bdb7fd-rqg96   0/2     Pending       0          0s
hello-world-deployment-7ff4bdb7fd-rqg96   0/2     ContainerCreating   0          0s
hello-world-deployment-7ff4bdb7fd-rqg96   1/2     Running             0          1s
hello-world-deployment-7ff4bdb7fd-rqg96   2/2     Running             0          1s

过一段时间没有新的请求后，pod会自动被删除，同时可以看到deployment的副本数缩成0。该namespace下并没有对应的hpa产生，说明deployment副本数的调整并非使用k8s原生的hpa机制。

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hello-world-deployment-7ff4bdb7fd-rqg96   2/2     Terminating         0          63s
hello-world-deployment-7ff4bdb7fd-rqg96   0/2     Terminating         0          93s
$ k get deployments.apps 
NAME                     READY   UP-TO-DATE   AVAILABLE   AGE
hello-world-deployment   0/0     0            0           21h

service的流量切分

重新提交如下的yaml文件，将service对应的revision更新为knative。

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apiVersion: serving.knative.dev/v1
kind: Service
metadata:
  name: hello
spec:
  template:
    metadata:
      name: hello-knative
    spec:
      containers:
        - image: gcr.io/knative-samples/helloworld-go
          ports:
            - containerPort: 8080
          env:
            - name: TARGET
              value: "Knative"

重新查看revision，可以看到revision已经变更为了knative，同时可以看到老的revision world并没有被删除，只是没有了流量转发。

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$ kn revision list
NAME            SERVICE   TRAFFIC   TAGS   GENERATION   AGE   CONDITIONS   READY   REASON
hello-knative   hello     100%             2            49s   4 OK / 4     True    
hello-world     hello                      1            10m   3 OK / 4     True

重新apply新的Service，将流量切分为hello-world和hello-knative两份，重新执行curl请求，可以看到结果会随机返回。

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apiVersion: serving.knative.dev/v1
kind: Service
metadata:
  name: hello
spec:
  template:
    metadata:
      name: hello-knative
    spec:
      containers:
        - image: gcr.io/knative-samples/helloworld-go
          ports:
            - containerPort: 8080
          env:
            - name: TARGET
              value: "Knative"
  traffic:
  - latestRevision: true
    percent: 50
  - revisionName: hello-world
    percent: 50

查看revision的信息，可以看到流量已经是50%的切分了。

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# kn revision list              
NAME            SERVICE   TRAFFIC   TAGS   GENERATION   AGE   CONDITIONS   READY   REASON
hello-knative   hello     50%              2            11m   3 OK / 4     True    
hello-world     hello     50%              1            21m   3 OK / 4     True

knative eventing

image.png
Source：k8s的CR对象，产生Event
Broker：用来分发Event
Trigger：Event触发器
Sink：Event输出结果

其中包含业务逻辑的可编程的部分在于Trigger部分，由于trigger实际上是无状态的服务，对于一些有状态的消息knative很难满足。比如同一类型的特定字段的event转发到特定的trigger上，broker实际上不具备可编程性，因此无法完成。

kn quickstart 命令会安装一个broker到环境中

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$ k get brokers.eventing.knative.dev example-broker -o yaml 
apiVersion: eventing.knative.dev/v1
kind: Broker
metadata:
  annotations:
    eventing.knative.dev/broker.class: MTChannelBasedBroker
    eventing.knative.dev/creator: kubernetes-admin
    eventing.knative.dev/lastModifier: kubernetes-admin
  name: example-broker
  namespace: default
spec:
  config:
    apiVersion: v1
    kind: ConfigMap
    name: config-br-default-channel
    namespace: knative-eventing
  delivery:
    backoffDelay: PT0.2S
    backoffPolicy: exponential
    retry: 10
status:
  address:
    url: http://broker-ingress.knative-eventing.svc.cluster.local/default/example-broker
  annotations:
    knative.dev/channelAPIVersion: messaging.knative.dev/v1
    knative.dev/channelAddress: http://example-broker-kne-trigger-kn-channel.default.svc.cluster.local
    knative.dev/channelKind: InMemoryChannel
    knative.dev/channelName: example-broker-kne-trigger
  conditions:
  - lastTransitionTime: "2022-03-11T12:32:43Z"
    status: "True"
    type: Addressable
  - lastTransitionTime: "2022-03-11T12:32:43Z"
    message: No dead letter sink is configured.
    reason: DeadLetterSinkNotConfigured
    severity: Info
    status: "True"
    type: DeadLetterSinkResolved
  - lastTransitionTime: "2022-03-11T12:32:43Z"
    status: "True"
    type: FilterReady
  - lastTransitionTime: "2022-03-11T12:32:43Z"
    status: "True"
    type: IngressReady
  - lastTransitionTime: "2022-03-11T12:32:43Z"
    status: "True"
    type: Ready
  - lastTransitionTime: "2022-03-11T12:32:43Z"
    status: "True"
    type: TriggerChannelReady
  observedGeneration: 1

快速开始

创建如下的Service，该service通过环境变量 BROKER_URL 作为broker地址，可以看到其地址为 quickstart工具默认安装的example-broker。

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apiVersion: serving.knative.dev/v1
kind: Service
metadata:
  name: cloudevents-player
spec:
  template:
    metadata:
      annotations:
        autoscaling.knative.dev/min-scale: "1"
    spec:
      containers:
        - image: ruromero/cloudevents-player:latest
          env:
            - name: BROKER_URL
              value: http://broker-ingress.knative-eventing.svc.cluster.local/default/example-broker

访问service页面 http://cloudevents-player.default.127.0.0.1.sslip.io/ 可以在界面上创建Event后，产生如下的Event内容，格式完全遵循社区的CloudEvent规范。点击发送，即可以将消息发送给broker，但由于borker没有配置任何的Trigger，消息在发送到broker后会被直接丢弃。

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{
  "root": {
    "attributes": {
      "datacontenttype": "application/json",
      "id": "123",
      "mediaType": "application/json",
      "source": "manual",
      "specversion": "1.0",
      "type": "test-type"
    },
    "data": {
      "message": "Hello CloudEvents!"
    },
    "extensions": {}
  }
}

我们继续来给broker增加触发器，创建如下的yaml。该触发器定义了broker为example-broker，

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apiVersion: eventing.knative.dev/v1
kind: Trigger
metadata:
  name: cloudevents-trigger
  annotations:
    knative-eventing-injection: enabled
spec:
  broker: example-broker
  subscriber:
    ref:
      apiVersion: serving.knative.dev/v1
      kind: Service
      name: cloudevents-player

重新在页面上发送event，可以看到消息的状态为接收。

参考