Add Kafka Sink

[aslom]

Expected Behavior

Allow Knative sink to send events to Kafka - symmetrical to Kafka source

Actual Behavior

Not possible with code in Knative eventing

Steps to Reproduce the Problem

1. Use event-display as sink to print events

Additional Info

Based on comments @jamesward

[jamesward]

Thanks! Sorry I didn't file this.

[aslom]

/good-first-issue

[n3wscott]

There is nothing special about a sink aside from being addressable.

For example, in google/knative-gcp, it models pubsub. I created a PullSubscription backed by a deployment, and also created a Topic backed by a ksvc. A channel combines both into do what we think of the thing we want channels to do. But the components are independently useful.

PullSubscription adheres to the Source contract, and Topic adheres to the Addressable contract.

This is not a good first issue as it is open ended and unclear what should be produced.

/remove-good-first-issue

[n3wscott]

My advice would be to make the same kind of object for Kafka to model the outbound Topic as I have for Topic for Pub/Sub.

[aslom]

@n3wscott interesting - can I deploy only Topic component as a knative sink for gcp pubsub? Where can I find an example of it? My thinking for good first issue was that functionality is very simple could be run just with command line arguments without need to use CR.

[aslom]

I wrote my own in Python as I needed it for testing - maybe I add and we refactor it as needed? I think there is real need for it - there are external Kafka brokers where you want your events to go ...

[aslom]

/assign

[aslom]

First version is in PR #1406

It is fully working Kafka Sink that can be deployed in k8s cluster.

Next steps are to add security, unit tests (not sure how to mock sending to Kafka topic?), create KafkaSink CR and add controller reconciliation support for it

[slinkydeveloper]

Done in knative-extensions/eventing-kafka-broker#134