容器服务Docker K8S

Sequeue 解析

2019-12-24 00:00:00 mimukeji

本文选自《Knative 云原生应用开发指南》
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Sequence 定义

首先我们看一下 Sequence Spec 定义:

apiVersion: messaging.knative.dev/v1alpha1
kind: Sequence
metadata:
  name: test
spec:
  channelTemplate:
    apiVersion: messaging.knative.dev/v1alpha1
    kind: InMemoryChannel
  steps:
    - ref:
        apiVersion: serving.knative.dev/v1alpha1
        kind: Service
        name: test
  reply:
    kind: Broker
    apiVersion: eventing.knative.dev/v1alpha1
    name: test

Sequence Spec包括3个部分:

  1. steps: 在 step 中定义了按照顺序执行的服务,每个服务会对应创建 Subscription
  2. channelTemplate:指定了使用具体的那个 Channel
  3. reply:(可选)定义了将最后一个 step 服务结果转发到的目标服务

Sequence 都是适合哪些具体应用场景呢?我们上面也提到了事件处理的 Pipeline。那么在实际场景应用中究竟以什么样的形式体现呢? 现在我们揭晓一下 Sequence 在 Knative Eventing 中提供的如下 4 种使用场景:

  • 直接访问 Service
  • 面向事件处理
  • 级联 Sequence
  • 面向 Broker/Trigger

直接访问 Service 场景

事件源产生的事件直接发送给 Sequence 服务, Sequence 接收到事件之后顺序调用 Service 服务对事件进行处理:
20.png

创建 Knative Service

这里我们创建 3 个 Knative Service 用于事件处理。每个 Service 接收到事件之后会打印当前的事件处理信息。

apiVersion: serving.knative.dev/v1alpha1
kind: Service
metadata:
  name: first
spec:
  template:
    spec:
      containers:
        - image: registry.cn-hangzhou.aliyuncs.com/knative-sample/probable-summer:2656f39a7fcb6afd9fc79e7a4e215d14d651dc674f38020d1d18c6f04b220700
          env:
            - name: STEP
              value: "0"

---
apiVersion: serving.knative.dev/v1alpha1
kind: Service
metadata:
  name: second
spec:
  template:
    spec:
      containers:
        - image: registry.cn-hangzhou.aliyuncs.com/knative-sample/probable-summer:2656f39a7fcb6afd9fc79e7a4e215d14d651dc674f38020d1d18c6f04b220700
          env:
            - name: STEP
              value: "1"
---
apiVersion: serving.knative.dev/v1alpha1
kind: Service
metadata:
  name: third
spec:
  template:
    spec:
      containers:
        - image: registry.cn-hangzhou.aliyuncs.com/knative-sample/probable-summer:2656f39a7fcb6afd9fc79e7a4e215d14d651dc674f38020d1d18c6f04b220700
          env:
            - name: STEP
              value: "2"
---

创建 Sequence

创建顺序调用 first->second->third Service 的 Sequence。

apiVersion: messaging.knative.dev/v1alpha1
kind: Sequence
metadata:
  name: sequence
spec:
  channelTemplate:
    apiVersion: messaging.knative.dev/v1alpha1
    kind: InMemoryChannel
  steps:
    - ref:
        apiVersion: serving.knative.dev/v1alpha1
        kind: Service
        name: first
    - ref:
        apiVersion: serving.knative.dev/v1alpha1
        kind: Service
        name: second
    - ref:
        apiVersion: serving.knative.dev/v1alpha1
        kind: Service
        name: third

创建数据源

创建 CronJobSource 数据源,每隔 1 分钟发送一条事件消息{"message": "Hello world!"}到 Sequence 服务。

apiVersion: sources.eventing.knative.dev/v1alpha1
kind: CronJobSource
metadata:
  name: cronjob-source
spec:
  schedule: "*/1 * * * *"
  data: '{"message": "Hello world!"}'
  sink:
    apiVersion: messaging.knative.dev/v1alpha1
    kind: Sequence
    name: sequence

示例结果

21.png22.png
23.png
24.png

面向事件处理场景

事件源产生的事件直接发送给 Sequence 服务, Sequence 接收到事件之后顺序调用 Service 服务对事件进行处理,处理之后的最终结果会调用event-display Service 显示:
25.png

创建 Knative Service

同上创建 3 个 Knative Service 用于事件处理:

apiVersion: serving.knative.dev/v1alpha1
kind: Service
metadata:
  name: first
spec:
  template:
    spec:
      containers:
        - image: registry.cn-hangzhou.aliyuncs.com/knative-sample/probable-summer:2656f39a7fcb6afd9fc79e7a4e215d14d651dc674f38020d1d18c6f04b220700
          env:
            - name: STEP
              value: "0"

---
apiVersion: serving.knative.dev/v1alpha1
kind: Service
metadata:
  name: second
spec:
  template:
    spec:
      containers:
        - image: registry.cn-hangzhou.aliyuncs.com/knative-sample/probable-summer:2656f39a7fcb6afd9fc79e7a4e215d14d651dc674f38020d1d18c6f04b220700
          env:
            - name: STEP
              value: "1"
---
apiVersion: serving.knative.dev/v1alpha1
kind: Service
metadata:
  name: third
spec:
  template:
    spec:
      containers:
        - image: registry.cn-hangzhou.aliyuncs.com/knative-sample/probable-summer:2656f39a7fcb6afd9fc79e7a4e215d14d651dc674f38020d1d18c6f04b220700
          env:
            - name: STEP
              value: "2"
---

创建 Sequence

创建顺序调用 first->second->third Service 的 Sequence,将处理结果通过reply发送给event-display

apiVersion: messaging.knative.dev/v1alpha1
kind: Sequence
metadata:
  name: sequence
spec:
  channelTemplate:
    apiVersion: messaging.knative.dev/v1alpha1
    kind: InMemoryChannel
  steps:
    - ref:
        apiVersion: serving.knative.dev/v1alpha1
        kind: Service
        name: first
    - ref:
        apiVersion: serving.knative.dev/v1alpha1
        kind: Service
        name: second
    - ref:
        apiVersion: serving.knative.dev/v1alpha1
        kind: Service
        name: third
  reply:
    kind: Service
    apiVersion: serving.knative.dev/v1alpha1
    name: event-display

创建结果显示 Service

创建event-display Service, 用于接收最终的结果信息。

apiVersion: serving.knative.dev/v1alpha1
kind: Service
metadata:
  name: event-display
spec:
  template:
    spec:
      containers:
        - image: registry.cn-hangzhou.aliyuncs.com/knative-release/event_display:bf45b3eb1e7fc4cb63d6a5a6416cf696295484a7662e0cf9ccdf5c080542c21d

创建数据源

创建 CronJobSource 数据源,每隔 1 分钟发送一条事件消息{"message": "Hello world!"}到 Sequence 服务。

apiVersion: sources.eventing.knative.dev/v1alpha1
kind: CronJobSource
metadata:
  name: cronjob-source
spec:
  schedule: "*/1 * * * *"
  data: '{"message": "Hello world!"}'
  sink:
    apiVersion: messaging.knative.dev/v1alpha1
    kind: Sequence
    name: sequence

示例结果

26.png
27.png

级联 Sequence 场景

Sequence 更高级的地方还在于支持级联处理: Sequence By Sequence,这样可以进行多次 Sequence 处理,满足复杂事件处理场景需求:
28.png

创建 Knative Service

创建 6 个 Knative Service 用于事件处理, 前 3 个用于第 1 个 Sequence,后 3 个用于第 2 个 Sequence。

apiVersion: serving.knative.dev/v1alpha1
kind: Service
metadata:
  name: first
spec:
  template:
    spec:
      containers:
        - image: registry.cn-hangzhou.aliyuncs.com/knative-sample/probable-summer:2656f39a7fcb6afd9fc79e7a4e215d14d651dc674f38020d1d18c6f04b220700
          env:
            - name: STEP
              value: "0"

---
apiVersion: serving.knative.dev/v1alpha1
kind: Service
metadata:
  name: second
spec:
  template:
    spec:
      containers:
        - image: registry.cn-hangzhou.aliyuncs.com/knative-sample/probable-summer:2656f39a7fcb6afd9fc79e7a4e215d14d651dc674f38020d1d18c6f04b220700
          env:
            - name: STEP
              value: "1"
---
apiVersion: serving.knative.dev/v1alpha1
kind: Service
metadata:
  name: third
spec:
  template:
    spec:
      containers:
        - image: registry.cn-hangzhou.aliyuncs.com/knative-sample/probable-summer:2656f39a7fcb6afd9fc79e7a4e215d14d651dc674f38020d1d18c6f04b220700
          env:
            - name: STEP
              value: "2"
---
apiVersion: serving.knative.dev/v1alpha1
kind: Service
metadata:
  name: fourth
spec:
  template:
    spec:
      containers:
        - image: registry.cn-hangzhou.aliyuncs.com/knative-sample/probable-summer:2656f39a7fcb6afd9fc79e7a4e215d14d651dc674f38020d1d18c6f04b220700
          env:
            - name: STEP
              value: "3"

---
apiVersion: serving.knative.dev/v1alpha1
kind: Service
metadata:
  name: fifth
spec:
  template:
    spec:
      containers:
        - image: registry.cn-hangzhou.aliyuncs.com/knative-sample/probable-summer:2656f39a7fcb6afd9fc79e7a4e215d14d651dc674f38020d1d18c6f04b220700
          env:
            - name: STEP
              value: "4"
---
apiVersion: serving.knative.dev/v1alpha1
kind: Service
metadata:
  name: sixth
spec:
  template:
    spec:
      containers:
        - image: registry.cn-hangzhou.aliyuncs.com/knative-sample/probable-summer:2656f39a7fcb6afd9fc79e7a4e215d14d651dc674f38020d1d18c6f04b220700
          env:
            - name: STEP
              value: "5"
---

创建第 1 个 Sequence

使用 first->second->third Service 用于第 1 个 Sequence 调用处理,将执行结果发送给第 2 个 Sequence。

apiVersion: messaging.knative.dev/v1alpha1
kind: Sequence
metadata:
  name: first-sequence
spec:
  channelTemplate:
    apiVersion: messaging.knative.dev/v1alpha1
    kind: InMemoryChannel
  steps:
    - ref:
        apiVersion: serving.knative.dev/v1alpha1
        kind: Service
        name: first
    - ref:
        apiVersion: serving.knative.dev/v1alpha1
        kind: Service
        name: second
    - ref:
        apiVersion: serving.knative.dev/v1alpha1
        kind: Service
        name: third
  reply:
    kind: Sequence
    apiVersion: messaging.knative.dev/v1alpha1
    name: second-sequence

创建第 2 个 Sequence

使用 fourth->fifth->sixth Service 用于第 2 个 Sequence 调用处理,将执行结果发送给 event-display

apiVersion: messaging.knative.dev/v1alpha1
kind: Sequence
metadata:
  name: second-sequence
spec:
  channelTemplate:
    apiVersion: messaging.knative.dev/v1alpha1
    kind: InMemoryChannel
  steps:
    - ref:
        apiVersion: serving.knative.dev/v1alpha1
        kind: Service
        name: fourth
    - ref:
        apiVersion: serving.knative.dev/v1alpha1
        kind: Service
        name: fifth
    - ref:
        apiVersion: serving.knative.dev/v1alpha1
        kind: Service
        name: sixth
  reply:
    kind: Service
    apiVersion: serving.knative.dev/v1alpha1
    name: event-display

创建结果显示 Service

apiVersion: serving.knative.dev/v1alpha1
kind: Service
metadata:
  name: event-display
spec:
  template:
    spec:
      containerers:
        - image: registry.cn-hangzhou.aliyuncs.com/knative-release/event_display:bf45b3eb1e7fc4cb63d6a5a6416cf696295484a7662e0cf9ccdf5c080542c21d

创建数据源指向第 1 个 Sequence

apiVersion: sources.eventing.knative.dev/v1alpha1
kind: CronJobSource
metadata:
  name: cronjob-source
spec:
  schedule: "*/1 * * * *"
  data: '{"message": "Hello world!"}'
  sink:
    apiVersion: messaging.knative.dev/v1alpha1
    kind: Sequence
    name: first-sequence

示例结果

29.png
30.png

Broker/Trigger 场景

事件源 cronjobsource 向 Broker 发送事件,通过Trigger 将这些事件发送到由 3 个 Service 调用的 Sequence 中。Sequence 处理完之后将结果事件发送给 Broker,并最终由另一个Trigger发送给 event-display Service 显示事件结果:
31.png

创建 Knative Service

同上创建 3 个 Knative Service,用于 Sequence 中服务处理。

apiVersion: serving.knative.dev/v1alpha1
kind: Service
metadata:
  name: first
spec:
  template:
    spec:
      containers:
      - image: registry.cn-hangzhou.aliyuncs.com/knative-sample/probable-summer:2656f39a7fcb6afd9fc79e7a4e215d14d651dc674f38020d1d18c6f04b220700
        env:
        - name: STEP
          value: "0"

---
apiVersion: serving.knative.dev/v1alpha1
kind: Service
metadata:
  name: second
spec:
  template:
    spec:
      containers:
      - image: registry.cn-hangzhou.aliyuncs.com/knative-sample/probable-summer:2656f39a7fcb6afd9fc79e7a4e215d14d651dc674f38020d1d18c6f04b220700
        env:
        - name: STEP
          value: "1"
---
apiVersion: serving.knative.dev/v1alpha1
kind: Service
metadata:
  name: third
spec:
  template:
    spec:
      containers:
      - image: registry.cn-hangzhou.aliyuncs.com/knative-sample/probable-summer:2656f39a7fcb6afd9fc79e7a4e215d14d651dc674f38020d1d18c6f04b220700
        env:
        - name: STEP
          value: "2"

---

创建 Sequence

创建 Sequence,这里依次顺序执行first->second->third这3个服务。将最终处理的结果发送到broker-test中。

apiVersion: messaging.knative.dev/v1alpha1
kind: Sequence
metadata:
  name: sequence
spec:
  channelTemplate:
    apiVersion: messaging.knative.dev/v1alpha1
    kind: InMemoryChannel
  steps:
    - ref:
        apiVersion: serving.knative.dev/v1alpha1
        kind: Service
        name: first
    - ref:
        apiVersion: serving.knative.dev/v1alpha1
        kind: Service
        name: second
    - ref:
        apiVersion: serving.knative.dev/v1alpha1
        kind: Service
        name: third
  reply:
    kind: Broker
    apiVersion: eventing.knative.dev/v1alpha1
    name: default

创建事件源指向 Broker

创建 CronjobSource,它将每隔 1 分钟发送一条{"message": "Hello world!"}消息到 broker-test 中。

apiVersion: sources.eventing.knative.dev/v1alpha1
kind: CronJobSource
metadata:
  name: cronjob-source
spec:
  schedule: "*/1 * * * *"
  data: '{"message": "Hello world!"}'
  sink:
    apiVersion: eventing.knative.dev/v1alpha1
    kind: Broker
    name: default

创建 Broker

创建默认 Broker

kubectl label namespace default knative-eventing-injection=enabled

创建 Trigger  指向 Sequence

创建订阅事件类型为dev.knative.cronjob.event的 Trigger, 用于 Sequence 进行消费处理。

apiVersion: eventing.knative.dev/v1alpha1
kind: Trigger
metadata:
  name: sequence-trigger
spec:
  filter:
    sourceAndType:
      type: dev.knative.cronjob.event
  subscriber:
    ref:
      apiVersion: messaging.knative.dev/v1alpha1
      kind: Sequence
      name: sequence

创建结果订阅 Trigger

创建订阅 samples.http.mod3 的事件类型 Trigger,将 Sequence 执行的结果发送给event-display Service 进行显示。

apiVersion: eventing.knative.dev/v1alpha1
kind: Trigger
metadata:
  name: display-trigger
spec:
  filter:
    sourceAndType:
      type: samples.http.mod3
  subscriber:
    ref:
      apiVersion: serving.knative.dev/v1alpha1
      kind: Service
      name: event-display
---
apiVersion: serving.knative.dev/v1alpha1
kind: Service
metadata:
  name: event-display
spec:
  template:
    spec:
      containers:
        - image: registry.cn-hangzhou.aliyuncs.com/knative-release/event_display:bf45b3eb1e7fc4cb63d6a5a6416cf696295484a7662e0cf9ccdf5c080542c21d
---

示例结果

32.png
33.png

总结

以上介绍了什么是 Sequence, 以及基于 Sequence 的 4 种使用场景,我们可以根据实际需求选择不同的使用场景,从而实现事件处理 Pipeline。这对于需要多步骤处理事件的场景尤为适合。

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