[DO NOT SQUASH]: revert KIP-695

[vvcephei]

Reverts both commits in KIP-695, which is being postponed until after 2.8

Committer Checklist (excluded from commit message)

• Verify design and implementation
• Verify test coverage and CI build status
• Verify documentation (including upgrade notes)

[vvcephei]

Hey @guozhangwang , unfortunately, the revert wasn't clean. I kept the two commits separate (and intend to merge them separately).

I'm pretty sure I resolved the reversion correctly. Can you make a quick pass to double-check I didn't break something?

[chia7712]

@vvcephei Is this revert included by 2.9? If so, we can introduce the behavior in major release (3.0) straightforward.

[vvcephei]

Thanks, @chia7712 !

With all the recent feedback and no clear "best" option, I've gone back to the drawing board this week, and I think I've figured out a better way to do it. I was going to prepare a PR for trunk and then send a reply to the mailing list.

I decided to just revert the feature from 2.8 instead of changing the design and putting in a fresh implementation so long after feature freeze. I should have reverted it right away, since it's blocking the system tests; I was just hoping to rescue it for 2.8.

[vvcephei]

Hmm. The java 15 build passed, java 11 failed in the core SSL test (flaky), and java 8 "exited with a non-zero exit status" twice in a row. The Jenkins logs are a little hard to read, but it looks like it failed in the core integration tests, which pass for me using java 8.

I ran it locally on java 8, though, and it passes for me.

I'm running the Jenkins build again, and also running the full integration test suite in java 8 on my machine. If it continues to look like a flaky failure, I'll just go ahead and merge it.

[chia7712]

@vvcephei Could you please revise title to make it more clear?

[vvcephei]

Sure thing, @chia7712 . For the record, I don't plan to merge this PR normally.

I wanted to maintain a 1:1 relationship between the initial commits and their reversions, but just included them both in one PR for ease of review and testing.

Once the tests finish, I'll merge the commits individually and then close this PR.

Thanks for the review!

[vvcephei]

Ok, at least all the jvms completed the test suite this time, but I still see a set of "usual suspects" flaky tests:

    Build / JDK 8 / kafka.api.PlaintextAdminIntegrationTest.testDescribeLogDirs()
    Build / JDK 11 / org.apache.kafka.connect.integration.RebalanceSourceConnectorsIntegrationTest.testMultipleWorkersRejoining
    Build / JDK 15 / org.apache.kafka.connect.integration.BlockingConnectorTest.testBlockInSinkTaskStart
    Build / JDK 15 / org.apache.kafka.streams.integration.KTableKTableForeignKeyInnerJoinMultiIntegrationTest.shouldInnerJoinMultiPartitionQueryable

I have checked and see these same tests failing on 2.8, so I will proceed to merge and hopefully getting the system tests unblocked.

[vvcephei]

I merged the two commits from this PR after rebasing them.