chia7712 commented on code in PR #18685:
URL: https://github.com/apache/kafka/pull/18685#discussion_r1985530280
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core/src/main/scala/kafka/server/metadata/KRaftMetadataCache.scala:
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@@ -522,10 +522,14 @@ class KRaftMetadataCache(
if (kraftVersionLevel > 0) {
finalizedFeatures.put(KRaftVersion.FEATURE_NAME, kraftVersionLevel)
}
+ var metadataVersion = MetadataVersion.MINIMUM_VERSION
+ if (!image.features().metadataVersion().isEmpty) {
+ metadataVersion = image.features().metadataVersionOrThrow()
+ }
new FinalizedFeatures(
- image.features().metadataVersionOrThrow(),
+ metadataVersion,
finalizedFeatures,
- image.highestOffsetAndEpoch().offset)
+ image.highestOffsetAndEpoch().epoch())
Review Comment:
@junrao Thank you for your explanation. The following question may not be a
real issue in Kafka, and I'm simply trying to learn more about the design.
> In the client, the way that FinalizedFeaturesEpoch is used is to decide
which finalized features returned in ApiResponse is the latest.
The `FinalizedFeaturesEpoch` keeps increasing over time (due to
`NoOpRecord`), so how do we use it to determine the "latest" ApiResponse, since
the value is always greater than the previous ApiResponse?
For example: Clients may periodically update the `ApiResponse` and compare
the latest `FinalizedFeaturesEpoch` with their local cached
`FinalizedFeaturesEpoch`. If the latest `FinalizedFeaturesEpoch` is greater
than the local cached `FinalizedFeaturesEpoch`, clients initiate local feature
changes. However, since the latest `FinalizedFeaturesEpoch` is always greater
than the local cached `FinalizedFeaturesEpoch`, checking it becomes unnecessary.
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