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Getting Started with Knative Eventing
After you install Knative Eventing, you can create, send, and verify events. This guide shows how you can use a basic workflow for managing events.
Before you start to manage events, you must create the objects needed to transport the events.
Creating a Knative Eventing namespace
Namespaces are used to group together and organize your Knative resources.
Create a new namespace called event-example
by entering the following command:
kubectl create namespace event-example
Adding a broker to the namespace
The broker allows you to route events to different event sinks or consumers.
-
Add a broker named
default
to your namespace by entering the following command:kubectl create -f - <<EOF apiVersion: eventing.knative.dev/v1 kind: broker metadata: name: default namespace: event-example EOF
-
Verify that the broker is working correctly, by entering the following command:
kubectl -n event-example get broker default
This shows information about your broker. If the broker is working correctly, it shows a
READY
status ofTrue
:NAME READY REASON URL AGE default True http://broker-ingress.knative-eventing.svc.cluster.local/event-example/default 1m
If
READY
isFalse
, wait a few moments and then run the command again. If you continue to receive theFalse
status, see the Debugging Guide to troubleshoot the issue.
Creating event consumers
In this step, you create two event consumers, hello-display
and goodbye-display
, to
demonstrate how you can configure your event producers to target a specific consumer.
-
To deploy the
hello-display
consumer to your cluster, run the following command:kubectl -n event-example apply -f - << EOF apiVersion: apps/v1 kind: Deployment metadata: name: hello-display spec: replicas: 1 selector: matchLabels: &labels app: hello-display template: metadata: labels: *labels spec: containers: - name: event-display image: gcr.io/knative-releases/knative.dev/eventing-contrib/cmd/event_display --- kind: Service apiVersion: v1 metadata: name: hello-display spec: selector: app: hello-display ports: - protocol: TCP port: 80 targetPort: 8080 EOF
-
To deploy the
goodbye-display
consumer to your cluster, run the following command:kubectl -n event-example apply -f - << EOF apiVersion: apps/v1 kind: Deployment metadata: name: goodbye-display spec: replicas: 1 selector: matchLabels: &labels app: goodbye-display template: metadata: labels: *labels spec: containers: - name: event-display # Source code: https://github.com/knative/eventing-contrib/tree/master/cmd/event_display image: gcr.io/knative-releases/knative.dev/eventing-contrib/cmd/event_display --- kind: Service apiVersion: v1 metadata: name: goodbye-display spec: selector: app: goodbye-display ports: - protocol: TCP port: 80 targetPort: 8080 EOF
-
Verify that the event consumers are working by entering the following command:
kubectl -n event-example get deployments hello-display goodbye-display
This lists the
hello-display
andgoodbye-display
consumers that you deployed:NAME READY UP-TO-DATE AVAILABLE AGE hello-display 1/1 1 1 26s goodbye-display 1/1 1 1 16s
The number of replicas in the READY column should match the number of replicas in the AVAILABLE column. If the numbers do not match, see the Debugging Guide to troubleshoot the issue.
Creating triggers
A trigger defines the events that each event consumer receives. Brokers use triggers to forward events to the correct consumers. Each trigger can specify a filter that enables selection of relevant events based on the Cloud Event context attributes.
-
Create a trigger by entering the following command:
kubectl -n event-example apply -f - << EOF apiVersion: eventing.knative.dev/v1 kind: Trigger metadata: name: hello-display spec: broker: default filter: attributes: type: greeting subscriber: ref: apiVersion: v1 kind: Service name: hello-display EOF
The command creates a trigger that sends all events of type
greeting
to your event consumer namedhello-display
. -
To add a second trigger, enter the following command:
kubectl -n event-example apply -f - << EOF apiVersion: eventing.knative.dev/v1 kind: Trigger metadata: name: goodbye-display spec: broker: default filter: attributes: source: sendoff subscriber: ref: apiVersion: v1 kind: Service name: goodbye-display EOF
The command creates a trigger that sends all events of source
sendoff
to your event consumer namedgoodbye-display
. -
Verify that the triggers are working correctly by running the following command:
kubectl -n event-example get triggers
This returns the
hello-display
andgoodbye-display
triggers that you created:NAME READY REASON BROKER SUBSCRIBER_URI AGE goodbye-display True default http://goodbye-display.event-example.svc.cluster.local/ 9s hello-display True default http://hello-display.event-example.svc.cluster.local/ 16s
If the triggers are correctly configured, they will be ready and pointing to the correct broker (
default
) andSUBSCRIBER_URI
.The
SUBSCRIBER_URI
has a value similar totriggerName.namespaceName.svc.cluster.local
. The exact value depends on the broker implementation. If this value looks incorrect, see the Debugging Guide to troubleshoot the issue.
Creating a pod as an event producer
This guide uses curl
commands to manually send individual events as HTTP requests to the broker, and demonstrate how these events are received by the correct event consumer.
The broker can only be accessed from within the cluster where Knative Eventing is installed. You must create a pod within that cluster to act as an event producer that will execute the curl
commands.
To create a pod, enter the following command:
kubectl -n event-example apply -f - << EOF
apiVersion: v1
kind: Pod
metadata:
labels:
run: curl
name: curl
spec:
containers:
# This could be any image that we can SSH into and has curl.
- image: radial/busyboxplus:curl
imagePullPolicy: IfNotPresent
name: curl
resources: {}
stdin: true
terminationMessagePath: /dev/termination-log
terminationMessagePolicy: File
tty: true
EOF
Sending events to the broker
-
SSH into the pod by running the following command:
kubectl -n event-example attach curl -it
You will see a prompt similar to the following:
Defaulting container name to curl. Use 'kubectl describe pod/ -n event-example' to see all of the containers in this pod. If you don't see a command prompt, try pressing enter. [ root@curl:/ ]$
-
Make a HTTP request to the broker. To show the various types of events you can send, you will make three requests:
-
To make the first request, which creates an event that has the
type
greeting
, run the following in the SSH terminal:curl -v "http://broker-ingress.knative-eventing.svc.cluster.local/event-example/default" \ -X POST \ -H "Ce-Id: say-hello" \ -H "Ce-Specversion: 1.0" \ -H "Ce-Type: greeting" \ -H "Ce-Source: not-sendoff" \ -H "Content-Type: application/json" \ -d '{"msg":"Hello Knative!"}'
When the broker receives your event,
hello-display
will activate and send it to the event consumer of the same name. If the event has been received, you will receive a202 Accepted
response similar to the one below:< HTTP/1.1 202 Accepted < Content-Length: 0 < Date: Mon, 12 Aug 2019 19:48:18 GMT
-
To make the second request, which creates an event that has the
source
sendoff
, run the following in the SSH terminal:curl -v "http://broker-ingress.knative-eventing.svc.cluster.local/event-example/default" \ -X POST \ -H "Ce-Id: say-goodbye" \ -H "Ce-Specversion: 1.0" \ -H "Ce-Type: not-greeting" \ -H "Ce-Source: sendoff" \ -H "Content-Type: application/json" \ -d '{"msg":"Goodbye Knative!"}'
When the broker receives your event,
goodbye-display
will activate and send the event to the event consumer of the same name. If the event has been received, you will receive a202 Accepted
response similar to the one below:< HTTP/1.1 202 Accepted < Content-Length: 0 < Date: Mon, 12 Aug 2019 19:48:18 GMT
-
To make the third request, which creates an event that has the
type
greeting
and thesource
sendoff
, run the following in the SSH terminal:curl -v "http://broker-ingress.knative-eventing.svc.cluster.local/event-example/default" \ -X POST \ -H "Ce-Id: say-hello-goodbye" \ -H "Ce-Specversion: 1.0" \ -H "Ce-Type: greeting" \ -H "Ce-Source: sendoff" \ -H "Content-Type: application/json" \ -d '{"msg":"Hello Knative! Goodbye Knative!"}'
When the broker receives your event,
hello-display
andgoodbye-display
will activate and send the event to the event consumer of the same name. If the event has been received, you will receive a202 Accepted
response similar to the one below:< HTTP/1.1 202 Accepted < Content-Length: 0 < Date: Mon, 12 Aug 2019 19:48:18 GMT
-
-
Exit SSH by typing
exit
into the command prompt.
You have sent two events to the hello-display
event consumer and two events to
the goodbye-display
event consumer (note that say-hello-goodbye
activates
the trigger conditions for both hello-display
and goodbye-display
). You
will verify that these events were received correctly in the next section.
Verifying that events were received
After you send the events, verify that the events were received by the correct subscribers.
- Look at the logs for the
hello-display
event consumer by entering the following command:kubectl -n event-example logs -l app=hello-display --tail=100
This returns the
Attributes
andData
of the events you sent tohello-display
:☁️ cloudevents.Event Validation: valid Context Attributes, specversion: 1.0 type: greeting source: not-sendoff id: say-hello time: 2019-05-20T17:59:43.81718488Z contenttype: application/json Extensions, knativehistory: default-broker-srk54-channel-24gls.event-example.svc.cluster.local Data, { "msg": "Hello Knative!" } ☁️ cloudevents.Event Validation: valid Context Attributes, specversion: 1.0 type: greeting source: sendoff id: say-hello-goodbye time: 2019-05-20T17:59:54.211866425Z contenttype: application/json Extensions, knativehistory: default-broker-srk54-channel-24gls.event-example.svc.cluster.local Data, { "msg": "Hello Knative! Goodbye Knative!" }
- Look at the logs for the
goodbye-display
event consumer by entering the following command:kubectl -n event-example logs -l app=goodbye-display --tail=100
This returns the
Attributes
andData
of the events you sent togoodbye-display
:☁️ cloudevents.Event Validation: valid Context Attributes, specversion: 1.0 type: not-greeting source: sendoff id: say-goodbye time: 2019-05-20T17:59:49.044926148Z contenttype: application/json Extensions, knativehistory: default-broker-srk54-channel-24gls.event-example.svc.cluster.local Data, { "msg": "Goodbye Knative!" } ☁️ cloudevents.Event Validation: valid Context Attributes, specversion: 1.0 type: greeting source: sendoff id: say-hello-goodbye time: 2019-05-20T17:59:54.211866425Z contenttype: application/json Extensions, knativehistory: default-broker-srk54-channel-24gls.event-example.svc.cluster.local Data, { "msg": "Hello Knative! Goodbye Knative!" }
Cleaning up example resources
You can delete the event-example
namespace and its associated resources from your cluster if you do not plan to use it again in the future.
Delete the event-example
namespace and all of its resources from your cluster by entering the following command:
kubectl delete namespace event-example
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