作者 | 元毅，阿里云容器平臺(tái)高級(jí)開發(fā)工程師，負(fù)責(zé)阿里云容器平臺(tái) Knative 相關(guān)工作。

導(dǎo)讀：在實(shí)際的開發(fā)中我們經(jīng)常會(huì)遇到將一條數(shù)據(jù)需要經(jīng)過(guò)多次處理的場(chǎng)景，稱為 Pipeline。那么在 Knative 中是否也提供這樣的能力呢？其實(shí)從 Knative Eventing 0.7 版本開始，就提供了 Sequence CRD 資源，用于事件處理 Pipeline。本篇文章中，阿里云容器平臺(tái)高級(jí)開發(fā)工程師元毅將為大家詳細(xì)介紹 Sequence 的定義及在 Knative Eventing 中提供的 4 種使用場(chǎng)景。

Sequence 定義

首先來(lái)看一下 Sequence Spec 定義：

apiVersion: messaging.knative.dev/v1alpha1 kind: Sequence metadata:name: test spec:channelTemplate:apiVersion: messaging.knative.dev/v1alpha1kind: InMemoryChannelsteps:- ref:apiVersion: serving.knative.dev/v1alpha1kind: Servicename: testreply:kind: BrokerapiVersion: eventing.knative.dev/v1alpha1name: test

Sequence Spec 包括 3 個(gè)部分：

steps： 在 step 中定義了按照順序執(zhí)行的服務(wù)，每個(gè)服務(wù)會(huì)對(duì)應(yīng)創(chuàng)建 Subscription；

channelTemplate：指定了使用具體的那個(gè) Channel；

reply：（可選）定義了將最后一個(gè) step 服務(wù)結(jié)果轉(zhuǎn)發(fā)到的目標(biāo)服務(wù)。

Sequence 都是適合哪些具體應(yīng)用場(chǎng)景呢？我們上面也提到了事件處理的 Pipeline。那么在實(shí)際場(chǎng)景應(yīng)用中究竟以什么樣的形式體現(xiàn)呢？ 現(xiàn)在我們揭曉一下 Sequence 在 Knative Eventing 中提供的如下 4 種使用場(chǎng)景：

• 直接訪問(wèn) Service；
• 面向事件處理；
• 級(jí)聯(lián) Sequence；
• 面向 Broker/Trigger。

直接訪問(wèn) Service 場(chǎng)景

事件源產(chǎn)生的事件直接發(fā)送給 Sequence 服務(wù)， Sequence 接收到事件之后順序調(diào)用 Service 服務(wù)對(duì)事件進(jìn)行處理：

創(chuàng)建 Knative Service

這里我們創(chuàng)建 3 個(gè) Knative Service 用于事件處理。每個(gè) Service 接收到事件之后會(huì)打印當(dāng)前的事件處理信息。

apiVersion: serving.knative.dev/v1alpha1 kind: Service metadata:name: first spec:template:spec:containers:- image: registry.cn-hangzhou.aliyuncs.com/knative-sample/probable-summer:2656f39a7fcb6afd9fc79e7a4e215d14d651dc674f38020d1d18c6f04b220700env:- name: STEPvalue: "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:2656f39a7fcb6afd9fc79e7a4e215d14d651dc674f38020d1d18c6f04b220700env:- name: STEPvalue: "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:2656f39a7fcb6afd9fc79e7a4e215d14d651dc674f38020d1d18c6f04b220700env:- name: STEPvalue: "2" ---

創(chuàng)建 Sequence

創(chuàng)建順序調(diào)用 first->second->third Service 的 Sequence。

apiVersion: messaging.knative.dev/v1alpha1 kind: Sequence metadata:name: sequence spec:channelTemplate:apiVersion: messaging.knative.dev/v1alpha1kind: InMemoryChannelsteps:- ref:apiVersion: serving.knative.dev/v1alpha1kind: Servicename: first- ref:apiVersion: serving.knative.dev/v1alpha1kind: Servicename: second- ref:apiVersion: serving.knative.dev/v1alpha1kind: Servicename: third

創(chuàng)建數(shù)據(jù)源

創(chuàng)建 CronJobSource 數(shù)據(jù)源，每隔 1 分鐘發(fā)送一條事件消息 {"message": "Hello world!"} 到 Sequence 服務(wù)。

apiVersion: sources.eventing.knative.dev/v1alpha1 kind: CronJobSource metadata:name: cronjob-source spec:schedule: "*/1 * * * *"data: '{"message": "Hello world!"}'sink:apiVersion: messaging.knative.dev/v1alpha1kind: Sequencename: sequence

示例結(jié)果

面向事件處理場(chǎng)景

事件源產(chǎn)生的事件直接發(fā)送給 Sequence 服務(wù)， Sequence 接收到事件之后順序調(diào)用 Service 服務(wù)對(duì)事件進(jìn)行處理，處理之后的最終結(jié)果會(huì)調(diào)用 event-display Service 顯示：

創(chuàng)建 Knative Service

同上創(chuàng)建 3 個(gè) Knative Service 用于事件處理：

apiVersion: serving.knative.dev/v1alpha1 kind: Service metadata:name: first spec:template:spec:containers:- image: registry.cn-hangzhou.aliyuncs.com/knative-sample/probable-summer:2656f39a7fcb6afd9fc79e7a4e215d14d651dc674f38020d1d18c6f04b220700env:- name: STEPvalue: "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:2656f39a7fcb6afd9fc79e7a4e215d14d651dc674f38020d1d18c6f04b220700env:- name: STEPvalue: "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:2656f39a7fcb6afd9fc79e7a4e215d14d651dc674f38020d1d18c6f04b220700env:- name: STEPvalue: "2" ---

創(chuàng)建 Sequence

創(chuàng)建順序調(diào)用 first->second->third Service 的 Sequence，將處理結(jié)果通過(guò) reply 發(fā)送給 event-display：

apiVersion: messaging.knative.dev/v1alpha1 kind: Sequence metadata:name: sequence spec:channelTemplate:apiVersion: messaging.knative.dev/v1alpha1kind: InMemoryChannelsteps:- ref:apiVersion: serving.knative.dev/v1alpha1kind: Servicename: first- ref:apiVersion: serving.knative.dev/v1alpha1kind: Servicename: second- ref:apiVersion: serving.knative.dev/v1alpha1kind: Servicename: thirdreply:kind: ServiceapiVersion: serving.knative.dev/v1alpha1name: event-display

創(chuàng)建結(jié)果顯示 Service

創(chuàng)建 event-display Service, 用于接收最終的結(jié)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

創(chuàng)建數(shù)據(jù)源

創(chuàng)建 CronJobSource 數(shù)據(jù)源，每隔 1 分鐘發(fā)送一條事件消息 {"message": "Hello world!"} 到 Sequence 服務(wù)。

apiVersion: sources.eventing.knative.dev/v1alpha1 kind: CronJobSource metadata:name: cronjob-source spec:schedule: "*/1 * * * *"data: '{"message": "Hello world!"}'sink:apiVersion: messaging.knative.dev/v1alpha1kind: Sequencename: sequence

示例結(jié)果

級(jí)聯(lián) Sequence 場(chǎng)景

Sequence 更高級(jí)的地方還在于支持級(jí)聯(lián)處理: Sequence By Sequence，這樣可以進(jìn)行多次 Sequence 處理，滿足復(fù)雜事件處理場(chǎng)景需求。

創(chuàng)建 Knative Service

創(chuàng)建 6 個(gè) Knative Service 用于事件處理， 前 3 個(gè)用于第 1 個(gè) Sequence，后 3 個(gè)用于第 2 個(gè) 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:2656f39a7fcb6afd9fc79e7a4e215d14d651dc674f38020d1d18c6f04b220700env:- name: STEPvalue: "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:2656f39a7fcb6afd9fc79e7a4e215d14d651dc674f38020d1d18c6f04b220700env:- name: STEPvalue: "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:2656f39a7fcb6afd9fc79e7a4e215d14d651dc674f38020d1d18c6f04b220700env:- name: STEPvalue: "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:2656f39a7fcb6afd9fc79e7a4e215d14d651dc674f38020d1d18c6f04b220700env:- name: STEPvalue: "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:2656f39a7fcb6afd9fc79e7a4e215d14d651dc674f38020d1d18c6f04b220700env:- name: STEPvalue: "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:2656f39a7fcb6afd9fc79e7a4e215d14d651dc674f38020d1d18c6f04b220700env:- name: STEPvalue: "5" ---

創(chuàng)建第 1 個(gè) Sequence

使用 first->second->third Service 用于第 1 個(gè) Sequence 調(diào)用處理，將執(zhí)行結(jié)果發(fā)送給第 2 個(gè) Sequence。

apiVersion: messaging.knative.dev/v1alpha1 kind: Sequence metadata:name: first-sequence spec:channelTemplate:apiVersion: messaging.knative.dev/v1alpha1kind: InMemoryChannelsteps:- ref:apiVersion: serving.knative.dev/v1alpha1kind: Servicename: first- ref:apiVersion: serving.knative.dev/v1alpha1kind: Servicename: second- ref:apiVersion: serving.knative.dev/v1alpha1kind: Servicename: thirdreply:kind: SequenceapiVersion: messaging.knative.dev/v1alpha1name: second-sequence

創(chuàng)建第 2 個(gè) Sequence

使用 fourth->fifth->sixth Service 用于第 2 個(gè) Sequence 調(diào)用處理，將執(zhí)行結(jié)果發(fā)送給 event-display。

apiVersion: messaging.knative.dev/v1alpha1 kind: Sequence metadata:name: second-sequence spec:channelTemplate:apiVersion: messaging.knative.dev/v1alpha1kind: InMemoryChannelsteps:- ref:apiVersion: serving.knative.dev/v1alpha1kind: Servicename: fourth- ref:apiVersion: serving.knative.dev/v1alpha1kind: Servicename: fifth- ref:apiVersion: serving.knative.dev/v1alpha1kind: Servicename: sixthreply:kind: ServiceapiVersion: serving.knative.dev/v1alpha1name: event-display

創(chuàng)建結(jié)果顯示 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

創(chuàng)建數(shù)據(jù)源指向第 1 個(gè) 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/v1alpha1kind: Sequencename: first-sequence

示例結(jié)果

Broker/Trigger 場(chǎng)景

事件源 cronjobsource 向 Broker 發(fā)送事件，通過(guò) Trigger 將這些事件發(fā)送到由 3 個(gè) Service 調(diào)用的 Sequence 中。Sequence 處理完之后將結(jié)果事件發(fā)送給 Broker，并最終由另一個(gè) Trigger 發(fā)送給 event-display Service 顯示事件結(jié)果:

創(chuàng)建 Knative Service

同上創(chuàng)建 3 個(gè) Knative Service，用于 Sequence 中服務(wù)處理。

apiVersion: serving.knative.dev/v1alpha1 kind: Service metadata:name: first spec:template:spec:containers:- image: registry.cn-hangzhou.aliyuncs.com/knative-sample/probable-summer:2656f39a7fcb6afd9fc79e7a4e215d14d651dc674f38020d1d18c6f04b220700env:- name: STEPvalue: "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:2656f39a7fcb6afd9fc79e7a4e215d14d651dc674f38020d1d18c6f04b220700env:- name: STEPvalue: "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:2656f39a7fcb6afd9fc79e7a4e215d14d651dc674f38020d1d18c6f04b220700env:- name: STEPvalue: "2"---

創(chuàng)建 Sequence

創(chuàng)建 Sequence，這里依次順序執(zhí)行 first->second->third 這 3 個(gè)服務(wù)。將最終處理的結(jié)果發(fā)送到 broker-test 中。

apiVersion: messaging.knative.dev/v1alpha1 kind: Sequence metadata:name: sequence spec:channelTemplate:apiVersion: messaging.knative.dev/v1alpha1kind: InMemoryChannelsteps:- ref:apiVersion: serving.knative.dev/v1alpha1kind: Servicename: first- ref:apiVersion: serving.knative.dev/v1alpha1kind: Servicename: second- ref:apiVersion: serving.knative.dev/v1alpha1kind: Servicename: thirdreply:kind: BrokerapiVersion: eventing.knative.dev/v1alpha1name: default

創(chuàng)建事件源指向 Broker

創(chuàng)建 CronjobSource，它將每隔 1 分鐘發(fā)送一條 {"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/v1alpha1kind: Brokername: default

創(chuàng)建 Broker

創(chuàng)建默認(rèn) Broker：

kubectl label namespace default knative-eventing-injection=enabled

創(chuàng)建 Trigger 指向 Sequence

創(chuàng)建訂閱事件類型為 dev.knative.cronjob.event 的 Trigger, 用于 Sequence 進(jìn)行消費(fèi)處理。

apiVersion: eventing.knative.dev/v1alpha1 kind: Trigger metadata:name: sequence-trigger spec:filter:sourceAndType:type: dev.knative.cronjob.eventsubscriber:ref:apiVersion: messaging.knative.dev/v1alpha1kind: Sequencename: sequence

創(chuàng)建結(jié)果訂閱 Trigger

創(chuàng)建訂閱 samples.http.mod3 的事件類型 Trigger，將 Sequence 執(zhí)行的結(jié)果發(fā)送給 event-display Service 進(jìn)行顯示。

apiVersion: eventing.knative.dev/v1alpha1 kind: Trigger metadata:name: display-trigger spec:filter:sourceAndType:type: samples.http.mod3subscriber:ref:apiVersion: serving.knative.dev/v1alpha1kind: Servicename: 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 ---

示例結(jié)果

小結(jié)

以上介紹了什么是 Sequence， 以及基于 Sequence 的 4 種使用場(chǎng)景，我們可以根據(jù)實(shí)際需求選擇不同的使用場(chǎng)景，從而實(shí)現(xiàn)事件處理 Pipeline。這對(duì)于需要多步驟處理事件的場(chǎng)景尤為適合。

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