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Sequence wired to event-display
We are going to create the following logical configuration. We create a
PingSource, feeding events to a Sequence
, then
taking the output of that Sequence
and displaying the resulting output.
The functions used in these examples live in https://github.com/knative/eventing-contrib/blob/master/cmd/appender/main.go.
Prerequisites
For this example, we’ll assume you have set up an InMemoryChannel
as well as
Knative Serving (for our functions). The examples use default
namespace,
again, if you want to deploy to another Namespace, you will need to modify the
examples to reflect this.
If you want to use different type of Channel
, you will have to modify the
Sequence.Spec.ChannelTemplate
to create the appropriate Channel resources.
Setup
Create the Knative Services
Change default
below to create the steps in the Namespace where you want
resources created.
apiVersion: serving.knative.dev/v1
kind: Service
metadata:
name: first
spec:
template:
spec:
containers:
- image: gcr.io/knative-releases/knative.dev/eventing-contrib/cmd/appender
env:
- name: MESSAGE
value: " - Handled by 0"
---
apiVersion: serving.knative.dev/v1
kind: Service
metadata:
name: second
spec:
template:
spec:
containers:
- image: gcr.io/knative-releases/knative.dev/eventing-contrib/cmd/appender
env:
- name: MESSAGE
value: " - Handled by 1"
---
apiVersion: serving.knative.dev/v1
kind: Service
metadata:
name: third
spec:
template:
spec:
containers:
- image: gcr.io/knative-releases/knative.dev/eventing-contrib/cmd/appender
env:
- name: MESSAGE
value: " - Handled by 2"
---
kubectl -n default create -f ./steps.yaml
Create the Sequence
The sequence.yaml
file contains the specifications for creating the Sequence.
If you are using a different type of Channel, you need to change the
spec.channelTemplate to point to your desired Channel.
apiVersion: flows.knative.dev/v1
kind: Sequence
metadata:
name: sequence
spec:
channelTemplate:
apiVersion: messaging.knative.dev/v1
kind: InMemoryChannel
steps:
- ref:
apiVersion: serving.knative.dev/v1
kind: Service
name: first
- ref:
apiVersion: serving.knative.dev/v1
kind: Service
name: second
- ref:
apiVersion: serving.knative.dev/v1
kind: Service
name: third
reply:
ref:
kind: Service
apiVersion: serving.knative.dev/v1
name: event-display
Change default
below to create the Sequence
in the Namespace where you want
the resources to be created.
kubectl -n default create -f ./sequence.yaml
Create the Service displaying the events created by Sequence
apiVersion: serving.knative.dev/v1
kind: Service
metadata:
name: event-display
spec:
template:
spec:
containers:
- image: gcr.io/knative-releases/knative.dev/eventing-contrib/cmd/event_display
Change default
below to create the Sequence
in the Namespace where you want
your resources to be created.
kubectl -n default create -f ./event-display.yaml
Create the PingSource targeting the Sequence
This will create a PingSource which will send a CloudEvent with {“message”: “Hello world!"} as the data payload every 2 minutes.
apiVersion: sources.knative.dev/v1beta2
kind: PingSource
metadata:
name: ping-source
spec:
schedule: "*/2 * * * *"
contentType: "application/json"
data: '{"message": "Hello world!"}'
sink:
ref:
apiVersion: flows.knative.dev/v1
kind: Sequence
name: sequence
kubectl -n default create -f ./ping-source.yaml
Inspecting the results
You can now see the final output by inspecting the logs of the event-display pods.
kubectl -n default get pods
Wait a bit and then look at the logs for the event-display pod:
kubectl -n default logs -l serving.knative.dev/service=event-display -c user-container --tail=-1
☁️ cloudevents.Event
Validation: valid
Context Attributes,
specversion: 1.0
type: samples.http.mode3
source: /apis/v1/namespaces/default/pingsources/ping-source
id: e8fa7906-ab62-4e61-9c13-a9406e2130a9
time: 2020-03-02T20:52:00.0004957Z
datacontenttype: application/json
Extensions,
knativehistory: sequence-kn-sequence-0-kn-channel.default.svc.cluster.local; sequence-kn-sequence-1-kn-channel.default.svc.cluster.local; sequence-kn-sequence-2-kn-channel.default.svc.cluster.local
traceparent: 00-6e2947379387f35ddc933b9190af16ad-de3db0bc4e442394-00
Data,
{
"id": 0,
"message": "Hello world! - Handled by 0 - Handled by 1 - Handled by 2"
}
And you can see that the initial PingSource message ("Hello World!")
has been
appended to it by each of the steps in the Sequence.
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