KAFKA-6793: Unused configuration logging appears to be noisy and unnecessary

[philipnee]

Reviving this old discussion, apparently the PR was closed so I reopened another one.

Issue: Recently we've encountered complaints about the warning being too noisy, therefore we want to reduce it to debug level.

The original PR was closed in : https://issues.apache.org/jira/browse/KAFKA-6793

Questions
Is this log useful at all? Should we just remove it?

[philipnee]

@hachikuji - info level logging to prevent misleading warn.

[hachikuji]

LGTM. Most of the time, this is an expected message, so info level seems more appropriate. At least we'll still have it in the logs in case it does hint at a real problem.

[philipnee]

Failing tests seem unrelated (also appear to be flaky)

Build / JDK 17 and Scala 2.13 / testGracefulClose() – org.apache.kafka.clients.consumer.KafkaConsumerTest
1s
Build / JDK 17 and Scala 2.13 / [1] Type=ZK, Name=testMigrate, MetadataVersion=3.4-IV0, Security=PLAINTEXT – kafka.zk.ZkMigrationIntegrationTest
9s
Build / JDK 8 and Scala 2.12 / testLargeAssignmentAndGroupWithNonEqualSubscription() – org.apache.kafka.clients.consumer.StickyAssignorTest
1m 30s
Build / JDK 8 and Scala 2.12 / [1] Type=ZK, Name=testMigrate, MetadataVersion=3.4-IV0, Security=PLAINTEXT – kafka.zk.ZkMigrationIntegrationTest
12s

[C0urante]

Huge +1 to demoting these. They've made the WARN level basically useless in Kafka Connect with the amount of noise they generate on startup, and the underlying strategy we use to track unused configs is just not intelligent enough to accommodate reasonable use cases like transparent passthrough of properties from one instantiated object to a plugin for it later on (i.e., after its AbstractConfig has already been instantiated).

[C0urante]

Thanks @philipnee!