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Using Sequence with Broker and Trigger
We are going to create the following logical configuration. We create a
PingSource, feeding events into the Broker, then we create a Filter
that wires
those events into a Sequence
consisting of 3
steps. Then we take the end of the Sequence and feed newly minted events back
into the Broker and create another Trigger which will then display those events.
Prerequisites
- Knative Serving
InMemoryChannel
NOTE: The examples use the default
namespace.
If you want to use different type of Channel
, you will have to modify the
Sequence.Spec.ChannelTemplate
to create the appropriate Channel resources.
The functions used in these examples live in https://github.com/knative/eventing-contrib/blob/master/cmd/appender/main.go.
Setup
Creating the Broker
To create the cluster default Broker type:
kubectl create -f - <<EOF
apiVersion: eventing.knative.dev/v1
kind: Broker
metadata:
name: default
EOF
Create the Knative Services
Change default
below to create the steps in the Namespace where you have
configured your Broker
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"
- name: TYPE
value: "samples.http.mod3"
---
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.
Also, change the spec.reply.name to point to your Broker
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: Broker
apiVersion: eventing.knative.dev/v1
name: default
Change default
below to create the Sequence
in the Namespace where you have
configured your Broker
.
kubectl -n default create -f ./sequence.yaml
Create the PingSource targeting the Broker
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/v1beta1
kind: PingSource
metadata:
name: ping-source
spec:
schedule: "*/2 * * * *"
jsonData: '{"message": "Hello world!"}'
sink:
ref:
apiVersion: eventing.knative.dev/v1
kind: Broker
name: default
Here, if you are using different type of Channel, you need to change the
spec.channelTemplate to point to your desired Channel. Also, change the
spec.reply.name to point to your Broker
Change default
below to create the Sequence
in the Namespace where you have
configured your Broker
.
kubectl -n default create -f ./ping-source.yaml
Create the Trigger targeting the Sequence
apiVersion: eventing.knative.dev/v1
kind: Trigger
metadata:
name: sequence-trigger
spec:
broker: default
filter:
attributes:
type: dev.knative.sources.ping
subscriber:
ref:
apiVersion: flows.knative.dev/v1
kind: Sequence
name: sequence
Change default
below to create the Sequence
in the Namespace where you have
configured your Broker
.
kubectl -n default create -f ./trigger.yaml
Create the Service and Trigger displaying the events created by Sequence
apiVersion: serving.knative.dev/v1
kind: Service
metadata:
name: sequence-display
spec:
template:
spec:
containers:
- image: gcr.io/knative-releases/knative.dev/eventing-contrib/cmd/appender
---
apiVersion: eventing.knative.dev/v1
kind: Trigger
metadata:
name: display-trigger
spec:
broker: default
filter:
attributes:
type: samples.http.mod3
subscriber:
ref:
apiVersion: serving.knative.dev/v1
kind: Service
name: sequence-display
---
Change default
below to create the Service
and Trigger
in the Namespace
where you have configured your Broker
.
kubectl -n default create -f ./display-trigger.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
Then look at the logs for the event-display pod:
kubectl -n default logs -l serving.knative.dev/service=sequence-display -c user-container --tail=-1
☁️ cloudevents.Event
Validation: valid
Context Attributes,
specversion: 1.0
type: samples.http.mod3
source: /apis/v1/namespaces/default/pingsources/ping-source
id: 159bba01-054a-4ae7-b7be-d4e7c5f773d2
time: 2020-03-03T14:56:00.000652027Z
datacontenttype: application/json
Extensions,
knativearrivaltime: 2020-03-03T14:56:00.018390608Z
knativehistory: default-kne-trigger-kn-channel.default.svc.cluster.local; 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; default-kne-trigger-kn-channel.default.svc.cluster.local
traceparent: 00-e893412106ff417a90a5695e53ffd9cc-5829ae45a14ed462-00
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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