Knative的事件驱动：Knative在OpenShift上的实践3
作者：互联网
一、Knative Eventing：点对点模式
我们知道Knative的两大核心组件：Serving和 Eventing。Serving部分在前面两篇文章已经介绍完了。本篇开始我们介绍Eventing。
Knative Eventing Sources是发出事件的软件。Source的工作是连接、消耗、捕获和潜在地缓冲事件。通常从外部系统，然后将这些事件中继到sink（接收器）。
Knative Eventing Sources are software components that emit events. The job of a Source is to connect to, drain, capture and potentially buffer events; often from an external system and then relay those events to the Sink.
Knative Eventing Sources默认自带以下四种类型：
# kubectl api-resources --api-group='sources.eventing.knative.dev'
我们首先看一个定义source的配置文件：
# cat eventinghello-source.yaml
上图标志位的含义：
1.定义了事件源的类型，事件系统即用型部署了一系列源，它还提供了部署自定义资源的方法
2.定义某一个的事件源类型的具体内容
Knative Eventing Sink可以指定event receiver（event consumer）。通过Event Source的配置中引用sink，可以设置点对点的通信，如下图所标的位置：
3.sink 可以是K8S或knative的service
4.此处我们将sind定义为Knative Service
5.sink被部署后的名字是eventinghello
检查配置文件：
# oc apply -f eventinghello-source.yaml
cronjobsource.sources.eventing.knative.dev/event-greeter-cronjob-source created
确认source部署成功：
#oc -n knativetutorial5 get cronjobsources.sources.eventing.knative.dev event-greeter-cronjob-source
source通过计划任务发出event，crontab在pod中运行：
运行以下命令以创建将用作cron事件的订阅服务器的Knative服务。下面配置将会创建knative service.
# cat eventing-hello-sink.yaml
查看knative service：
我们查看sink 对应pod的日志：
我们观察sink的pod，每两分钟接受一次消息，接受完毕后，无其他消息，pod会被杀掉。
二、Knative Eventing：Channel订阅模式
Channel通道是事件转发和持久层，其中每个通道都是单独的Kubernetes自定义资源。一个通道可以由Apache Kafka或InMemoryChannel支持。我们重点介绍InMemoryChannel。
订阅内容订阅是您注册服务以收听特定频道的方式。
channel或sink是event source和subscriber之间的接口。内置channel可存储传入事件并将事件数据分发给订户。在将事件转发给订户时，通道会根据CloudEvent规范转换事件数据。
创建event channel：
[root@lb.weixinyucluster ~/knative-tutorial/eventing]# cat channel.yaml
apiVersion: messaging.knative.dev/v1alpha1
kind: Channel
metadata:
name: eventinghello-ch
oc apply -n knativetutorial -f channel.yaml
# oc get inmemorychannel.messaging.knative.dev/eventinghello-ch
NAME READY REASON URL AGE
eventinghello-ch True http://eventinghello-ch-kn-channel.knativetutorial.svc.cluster.local 2m49s
event source监听外部事件，例如kafka主题或FTP服务器上的文件。它负责将接收到的事件及其数据排放到已配置的sink。
cat event-source.yaml
1.Channel API属于 api-group messaging.eventing.knative.dev
2. Kind是Channel而不是像之前那种指定为Knative的service
[root@lb.weixinyucluster ~/knative-tutorial/eventing]# oc apply -n knativetutorial -f event-sourcechch.yaml
cronjobsource.sources.eventing.knative.dev/my-cjs created
[root@lb.weixinyucluster ~/knative-tutorial/eventing]# oc -n knativetutorial get cronjobsources.sources.eventing.knative.dev
NAME READY AGE
my-cjs True 32s
创建Subscriber Services
[root@lb.weixinyucluster ~/knative-tutorial/eventing]# oc apply -n knativetutorial -f eventing-helloa-sink.yaml
service.serving.knative.dev/eventinghelloa created
[root@lb.weixinyucluster ~/knative-tutorial/eventing]# oc apply -n knativetutorial -f eventing-hellob-sink.yaml
service.serving.knative.dev/eventinghellob created
[root@lb.weixinyucluster ~/knative-tutorial/eventing]#
现在，为eventinghelloa创建适当的Subscription到Channel eventinghello-ch：
[root@lb.weixinyucluster ~/knative-tutorial/eventing]# oc apply -n knativetutorial -f eventing-helloa-sub.yaml
subscription.messaging.knative.dev/eventinghelloa-sub created
[root@lb.weixinyucluster ~/knative-tutorial/eventing]# oc apply -n knativetutorial -f eventing-hellob-sub.yaml
subscription.messaging.knative.dev/eventinghellob-sub created
[root@lb.weixinyucluster ~/knative-tutorial/eventing]#
查看pod：
查看pod的日志：# oc logs -f eventinghelloa-v1-deployment-5b6454fcd-cw9lh -c user-containe
# oc logs -f eventinghellob-v1-deployment-85bb64586f-n9tl7 -c user-container
我们看到两个knative service订阅者会受到的消息是相同的。
三、Knative Eventing：Triggers与Brokers模式
通过用knative-eventing-injection = enabled标记knativetutorial10命名空间，将使Knative Eventing部署默认的Knative Eventing Broker及其相关的Ingress：
# oc label namespace knativetutorial10 knative-eventing-injection=enabled
namespace/knativetutorial10 labeled
查看broker，已经部署成功：
现在，已经配置了broker，您需要创建sinks eventingaloha和eventingbonjour，它们将接收已过滤的事件。
# oc apply - -f eventing-aloha-sink.yaml
service.serving.knative.dev/eventingaloha created
# oc apply -f eventing-bonjour-sink.yaml
service.serving.knative.dev/eventingbonjour created
现在，为eventingaloha创建trigger，该trigger将过滤后的事件与service相关联：
# cat trigger-helloaloha.yaml
apiVersion: eventing.knative.dev/v1alpha1
kind: Trigger
metadata:
name: helloaloha
spec:
filter:
attributes:
type: greeting
subscriber:
ref:
apiVersion: serving.knative.dev/v1
kind: Service
name: eventingaloha
# oc apply -f trigger-helloaloha.yaml
trigger.eventing.knative.dev/helloaloha created
# cat trigger-hellobonjour.yaml
apiVersion: eventing.knative.dev/v1alpha1
kind: Trigger
metadata:
name: hellobonjour
spec:
filter:
attributes:
type: greeting
subscriber:
ref:
apiVersion: serving.knative.dev/v1
kind: Service
name: eventingbonjour
# oc apply -f trigger-hellobonjour.yaml
trigger.eventing.knative.dev/hellobonjour created
#oc get triggers.eventing.knative.dev helloaloha hellobonjour
找出eventhingaloha的subscriberURI：
# oc get trigger helloaloha -o yaml |grep -i subscriberUri
subscriberUri: http://eventingaloha.knativetutorial10.svc.cluster.local
# oc get trigger hellobonjour -o yaml |grep -i subscriberUri
subscriberUri: http://eventingbonjour.knativetutorial10.svc.cluster.local
找到broker’s subscriberURI:
# oc get broker default -o jsonpath='{.status.address.url}'
http://default-broker.knativetutorial10.svc.cluster.local
创建一个执行curl命令的pod：
[root@lb.weixinyucluster ~/knative-tutorial]# cat curler.yaml
apiVersion: v1
kind: Pod
metadata:
labels:
run: curler
name: curler
spec:
containers:
- name: curler
image: fedora:29
tty: true
curl eventingaloha的 subcriberURI
[root@lb.weixinyucluster ~/knative-tutorial]# oc apply -f curler.yaml
pod/curler created
[root@lb.weixinyucluster ~/knative-tutorial]# oc exec -it curler -- /bin/bash
[root@curler /]# curl -v "http://eventingaloha.knativetutorial10.svc.cluster.local" \
> -X POST \
> -H "Ce-Id: say-hello" \
> -H "Ce-Specversion: 1.0" \
> -H "Ce-Type: aloha" \
> -H "Ce-Source: mycurl" \
> -H "Content-Type: application/json" \
> -d '{"key":"from a curl"}'
curl eventingbonjour的subcriberURI
curl -v "http://eventingbonjour.knativetutorial10.svc.cluster.local" \
-X POST \
-H "Ce-Id: say-hello" \
-H "Ce-Specversion: 1.0" \
-H "Ce-Type: bonjour" \
-H "Ce-Source: mycurl" \
-H "Content-Type: application/json" \
-d '{"key":"from a curl"}'
接下来，通过curl broker的subcriberURI，同时触发eventingaloha 和 eventingbonjour：
curl -v "http://default-broker.knativetutorial10.svc.cluster.local" \
-X POST \
-H "Ce-Id: say-hello" \
-H "Ce-Specversion: 1.0" \
-H "Ce-Type: greeting" \
-H "Ce-Source: mycurl" \
-H "Content-Type: application/json" \
-d '{"key":"from a curl"}'
"Ce-Type: greeting"”是确保aloha和bonjour都对此事件做出响应的关键。
标签：eventing,oc,dev,事件驱动,knative,Ce,OpenShift,Knative 来源： https://blog.51cto.com/u_15127570/2711250