10-Flow

1 Knative Event Flow

• Importer

  • 连接至期望使用的第3方消息系统
  • 基于HTTP协议POST CloudEvents到Channel、Broker、Sequence/Parallel或Service/KService

• Channel

  • 支持多路订阅
  • 为订阅者“持久化”消息数据

• Service

  • 接收CloudEvents
  • （可选）回复处理后的数据

  

• Sequence

  • Kubernetes CRD资源类型
  • 串联多个Processor
  • 由多个有序的Step组成，每个step定义一个Subscriber
  • Step间的channel，由channeltemplate定义

  

• Parallel：根据不同的过滤条件对事件进行选择处理

  • Kubernetes CRD资源类型
  • 由多个条件式的并行Branch组成，每个Branch由一对Filter及Subscriber组成
    • 每个Filter即为一个Processor
  • Channel由由ChannelTemplate定义

  

2 Sequence Flow示例

• Sequence资源的期望状态（spec）主要包括三个字段

  • steps
    • 定义序列中的目的地(processor)列表
    • 按顺序调用
    • 每个step中还可以定义投递属性，主要定义event投递失败时的处理方案
  • channelTemplate
    • 指定要使用的ChannelCRD
    • 未指定时，将使用当前的namespace或者cluster中默认的Channel CRD
  • reply
    • 序列中最后一个subscriber处理后的信息所要发往的目的地

• 示例环境说明

  • Curl命令负责生成event
  • Event由Sequence中的各Step顺次处理
    • 各Step都运行一个appender应用
    • 分别向收到的数据尾部附加自定义的专有数据项
  • 最终结果发往ksvc/event-display，进行展示

  

• 准备实践环境

  • 定义Sequence里，三个step中的knative service

    kn service apply sq-appender-01 --image ikubernetes/appender --env MESSAGE=" - Handled by SQ-01"
     kn service apply sq-appender-02 --image ikubernetes/appender --env MESSAGE=" - Handled by SQ-02"
     $ kn service apply sq-appender-03 --image ikubernetes/appender --env MESSAGE=" - Handled by SQ-03"
    

    apiVersion: serving.knative.dev/v1
    kind: Service
    metadata:
      name: sq-appender-01
    spec:
      template:
        spec:
          containers:
            - image: ikubernetes/appender
              env:
                - name: MESSAGE
                  value: " - Handled by SQ-01"
    ---
    apiVersion: serving.knative.dev/v1
    kind: Service
    metadata:
      name: sq-appender-02
    spec:
      template:
        spec:
          containers:
            - image: ikubernetes/appender
              env:
                - name: MESSAGE
                  value: " - Handled by SQ-02"
    ---
    apiVersion: serving.knative.dev/v1
    kind: Service
    metadata:
      name: sq-appender-03
    spec:
      template:
        spec:
          containers:
            - image: ikubernetes/appender
              env:
                - name: MESSAGE
                  value: " - Handled by SQ-03"
    ---
    

    

  • 负责最后接收事件的Kservice/event-display

     kn service apply event-display --image=ikubernetes/event_display --port 8080 --scale-min 1 -n event-demo
    

    ---
    apiVersion: serving.knative.dev/v1
    kind: Service
    metadata:
      name: event-display
    spec:
      template:
        metadata:
          annotations:
            autoscaling.knative.dev/min-scale: "1"
        spec:
          containers:
            - image: ikubernetes/event_display
              ports:
                - containerPort: 8080
    

  • 创建Sequence资源

    apiVersion: flows.knative.dev/v1
    kind: Sequence
    metadata:
      name: sq-demo
    spec:
      channelTemplate:
        apiVersion: messaging.knative.dev/v1
        kind: InMemoryChannel
      steps:
        - ref:
            apiVersion: serving.knative.dev/v1
            kind: Service
            name: sq-appender-01
        - ref:
            apiVersion: serving.knative.dev/v1
            kind: Service
            name: sq-appender-02
        - ref:
            apiVersion: serving.knative.dev/v1
            kind: Service
            name: sq-appender-03
      reply:
        ref:
          kind: Service
          apiVersion: serving.knative.dev/v1
          name: event-display
    

    查看sequence资源：

    kubectl get sequences
    # URL中的地址，即为当前sequence的调用接口
    

    

  • 测试

    • 创建一个客户端Pod，使用curl命令基于HTTP协议推送event

       kubectl run client-$RANDOM --image=ikubernetes/admin-box:v1.2 --restart=Never --rm -it --command -- /bin/bash
      

    • 在启动的客户端Pod中，向Sequence/sq-demo的URL发起事件推送事件即可启动测试

       curl -v "http://sq-demo-kn-sequence-0-kn-channel.default.svc.cluster.local" -X POST -H "Content-Type: application/cloudevents+json" \
      -d '{"id": "0", "specversion": "1.0", "type": "com.icloud2native.sayhi", "source": "Curl", "data": {"message":"Hello Knative Eventing Flow"}}'
      

      

    • 在最后一个event-display的日志中查看事件

      

3 Parallel Flow 示例

• Parallel资源的期望状态（spec）主要包括三个字段

  • branches
    • 每个分支由一个filter和一个subscriber组成
    • filter负责定义过滤器，将符合条件的事件发给相应的subscriber
    • subscriber负责定义processor，将filter过滤的事件做相应处理
    • 结果发往reply或全局的reply
  • channelTemplate
    • 指定要使用的Channel CRD
    • 未指定时，将使用当前namespace或者Cluster中默认的Channel CRD
  • reply
    • 为所有branch处理后的信息定义一个全局目的地

• 示例环境说明

  • Curl命令负责生成event
  • Parallel中有两个Branch
    • 使用kservice/image-filter作为Filter，筛选类型为“com.icloud2native.file.image”的事件，相应的Subscriber为ksvc/paraappender-image，负责将该类事件信息标识为Image；
    • 使用kservice/text-filter作为Filter，筛选类型为“com.icloud2native.file.text”的事件，相应的Subscriber为ksvc/para-appender-text ，负责将该类事件信息标识为Text；
  • 所有分支的最终结果均发往ksvc/event-display，内容格式化CloudEvents存储入日志

  

• 具体步骤

  • 创建两个filter

    kn service apply image-filter --image villardl/filter-nodejs:0.1 --env FILTER='event.type == "com.icloud2native.file.image"'
    kn service apply text-filter --image villardl/filter-nodejs:0.1 --env FILTER='event.type == "com.icloud2native.file.text"'
    

    apiVersion: serving.knative.dev/v1
    kind: Service
    metadata:
      name: image-filter
    spec:
      template:
        spec:
          containers:
          - image: villardl/filter-nodejs:0.1
            env:
            - name: FILTER
              value: |
                event.type == "com.icloud2native.file.image"
    ---
    apiVersion: serving.knative.dev/v1
    kind: Service
    metadata:
      name: text-filter
    spec:
      template:
        spec:
          containers:
          - image: villardl/filter-nodejs:0.1
            env:
            - name: FILTER
              value: |
                event.type == "com.icloud2native.file.text"
    ---
    

    

  • 创建两个subscriber

    kn service apply para-appender-image --image ikubernetes/appender --env MESSAGE=" - filetype/Image"
    kn service apply para-appender-text --image ikubernetes/appender --env MESSAGE=" - filetype/Text"
    

    ---
    apiVersion: serving.knative.dev/v1
    kind: Service
    metadata:
      name: para-appender-image
    spec:
      template:
        spec:
          containers:
          - image: ikubernetes/appender
            env:
            - name: MESSAGE
              value: " - filetype/Image"
    ---
    apiVersion: serving.knative.dev/v1
    kind: Service
    metadata:
      name: para-appender-text
    spec:
      template:
        spec:
          containers:
          - image: ikubernetes/appender
            env:
            - name: MESSAGE
              value: " - filetype/Text"
    ---
    

    

  • 负责最后接收事件的Kservice/event-display

    kn service apply event-display --image=ikubernetes/event_display --port 8080 --scale-min 1
    

  • 创建并查看Parallel资源

    ---
    apiVersion: flows.knative.dev/v1
    kind: Parallel
    metadata:
      name: filetype-parallel
    spec:
      channelTemplate:
        apiVersion: messaging.knative.dev/v1
        kind: InMemoryChannel
      branches:
        - filter:
            ref:
              apiVersion: serving.knative.dev/v1
              kind: Service
              name: image-filter
          subscriber:
            ref:
              apiVersion: serving.knative.dev/v1
              kind: Service
              name: para-appender-image
        - filter:
            ref:
              apiVersion: serving.knative.dev/v1
              kind: Service
              name: text-filter
          subscriber:
            ref:
              apiVersion: serving.knative.dev/v1
              kind: Service
              name: para-appender-text
      reply:
        ref:
          apiVersion: serving.knative.dev/v1
          kind: Service
          name: event-display
    

    查看parallel资源

     kubectl get parallels
     # URL中的地址，即为当前Parallel资源的调用接
    

    

  • 测试

    • 创建一个客户端Pod，使用curl命令基于HTTP协议推送event

       kubectl run client-$RANDOM --image=ikubernetes/admin-box:v1.2 --restart=Never --rm -it --command -- /bin/bash
      

    • 在启动的客户端Pod中，向Parallel/filetype-parallel资源的URL发起事件推送事件即可启动测试

      # 首先推送一个类型为com.icloud2native.file.image的事件
       curl -v "http://filetype-parallel-kn-parallel-kn-channel.default.svc.cluster.local" -X POST \
      -H "Ce-Id: 0" \
      -H "Ce-Specversion: 1.0" \
      -H "Ce-Type: com.icloud2native.file.image" \
      -H "Ce-Source: Curl" \
      -H "Content-Type: application/json" \
      -d '{"message": "A uploaded file by a user"}'
      
      #  然后再推送一个类型为com.icloud2native.file.image的事件
       curl -v "http://filetype-parallel-kn-parallel-kn-channel.default.svc.cluster.local" -X POST \
      -H "Ce-Id: 0" \
      -H "Ce-Specversion: 1.0" \
      -H "Ce-Type: com.icloud2native.file.text" \
      -H "Ce-Source: Curl" \
      -H "Content-Type: application/json" \
      -d '{"message": "A uploaded file by a user"}'
      

    • 在ksvc/event-display的日志中查看事件数据，验证事件是否被不同的branch做了不同的处理