Modify kafka channel to use CRD

[akashrv]

Refer to decision made in #1002
This feature request is to update in-memory channel

[akashrv]

/milestone v0.7.0

[vaikas]

This should also move to messaging.knative.dev as part of that work as per.
https://github.com/knative/eventing/blob/master/docs/decisions/eventing-and-messaging.md

[nachocano]

@matzew are you planning on working on this one? If not, let me know and I can start with a first pass...

[matzew]

@nachocano I think that the next weeks I am good busy with this task:
#1213

Would you mind, starting? I am happy to help/review. when you port this to a KafkaChannel CRD

[nachocano]

Sounds good! Will start with this one then! Thanks!

…

On Mon, May 20, 2019 at 5:27 AM Matthias Wessendorf < ***@***.***> wrote: @nachocano <https://github.com/nachocano> I think that the next weeks I am good busy with this task: #1213 <#1213> Would you mind, starting? I am happy to help/review. when you port this to a KafkaChannel CRD — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#1216?email_source=notifications&email_token=ABD65DDDENE4RXWMYOW5YJLPWKKJRA5CNFSM4HMGOGAKYY3PNVWWK3TUL52HS4DFVREXG43VMVBW63LNMVXHJKTDN5WW2ZLOORPWSZGODVYU62Q#issuecomment-493965162>, or mute the thread <https://github.com/notifications/unsubscribe-auth/ABD65DH27EOEWQVBRCZ7Q43PWKKJRANCNFSM4HMGOGAA> .

[nachocano]

/assign

[nachocano]

This change seems bigger than I initially thought. Here are some of the items we need to get it done

• Create new KafkaChannel CRD, with types, validation, defaults, etc. [Kafka CRD, Controller, and Dispatcher #1261]
• Create new Kafka controller using pkg/controller. [Kafka CRD, Controller, and Dispatcher #1261]
• Create new Kafka dispatcher [Kafka CRD, Controller, and Dispatcher #1261]
• Create kafka admission webhook to set defaults [Kafka Webhook and Documentation #1316]
• Documentation [Kafka Webhook and Documentation #1316]
• E2E tests (this will be tracked in a separate issue Add E2E test to Kafka Channel CRD #1317) (Done by Chi)
• Controller UTs and Stats and Tracing (Kafka CRD Controller UT + Dispatcher tracing #1363)
• Migration plan. Similar to all channels

All the CRD changes for other channels will rely on changes to subscription validation:

• Subscription's channel: we need to change the webhook to allow any subscription.spec.channel kind (not just Channel as it is now) and then mark it as non-subscribable in the subscription controller if the object does not implement subscribable. As we cannot check properly for subscribable, then we we will check whether to the CRD has certain label. There is a follow up on creating a Channelable duck type

[Harwayne]

Subscription controller needs to watch the different channels (i.e., InMemoryChannel, KafkaChannel, GcpPubSubChannel, etc).

I think #1149 actually did this already. Namely it added code to track arbitrary CRDs and already passes the Channel as an ObjectReference to track.

[nachocano]

/reopen