Remove any existing finalizer

[vaikas]

Describe the bug
Prior to #4511 IMC would have finalizer. If this gets upgraded, then the IMC will not get removed. So, we should remove all the existing finalizers.

Expected behavior
Existing IMC after an upgrade to .20 will get properly deleted.

To Reproduce
Steps to reproduce the behavior.

Knative release version
0.20

Additional context
In 0.19, IMC dispatcher would set the finalizer so it would get removed. in #4511 we just deal with this in ReconcileKind, and hence after upgrading to this behaviour, any existing InMemoryChannels will have Finalizer set, but nothing that will clean it up. So, we should probably just remove those always in the Controller in case they are there. Need to test that they will be properly respected with genreconciler (nothing says they won't, but just need to verify this (for example, if it doesn't allow adding/removing additional finalizers)).

[slinkydeveloper]

@vaikas Is this still relevant? I see 0.20 as release

[lberk]

@vaikas is this issue still relevant? (v0.20 was released several weeks ago)

[antoineco]

I noticed that yesterday. All in-memory channels created before 0.20 are un-deletable because they contain a finalizer that no controller acts upon.

We are already on 0.21 so we can probably consider the damage done and move on. Or maybe provide a clean up script outside the regular releases for folks who ran into this. For example:

#!/usr/bin/env bash

kubectl get inmemorychannels.messaging.knative.dev -A -o json \
    | jq -r '.items[] | select(
          .metadata.deletionTimestamp != null
      ) | @base64' \
    | while read -r imc; do
          echo "$imc" | base64 -d \
          | kubectl patch -f- --type=json -p='[{"op": "remove", "path": "/metadata/finalizers"}]'
      done

Or change the condition in jq's select to remove the finalizers of all in-memory channels, not only the ones that are in deletion limbo:

#!/usr/bin/env bash

kubectl get inmemorychannels.messaging.knative.dev -A -o json \
    | jq -r '.items[] | select(
          .metadata.finalizers != null
      ) | @base64' \
    | while read -r imc; do
          echo "$imc" | base64 -d \
          | kubectl patch -f- --type=json -p='[{"op": "remove", "path": "/metadata/finalizers"}]'
      done

(I use this @base64 / base64 -d dance to ensure each API object is serialized as a single word, otherwise while read wouldn't work)

[grantr]

0.20 is old enough now that I don't think it's worth trying to fix this automatically. I added a note pointing to @antoineco's comment in the 0.20.0, 0.20.1, 0.20.2, and 0.20.3 release notes:

Known Issues

• InMemoryChannel objects created before release 0.20 may have an extra finalizer that blocks their deletion. Use the script in Remove any existing finalizer #4512 (comment) to remove the finalizers.