FrankYang0529 commented on code in PR #17444:
URL: https://github.com/apache/kafka/pull/17444#discussion_r1821004115
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group-coordinator/src/main/java/org/apache/kafka/coordinator/group/Utils.java:
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@@ -235,4 +238,20 @@ public static ApiMessage
messageOrNull(ApiMessageAndVersion apiMessageAndVersion
return apiMessageAndVersion.message();
}
}
+
+ public static long hashSubscriptionMetadata(Map<String, TopicMetadata>
subscriptionMetadata) {
Review Comment:
> When we replay records, we should only replay the persisted state. We
should not compute hashes there based on the metadata image there.
There are two parts of topic hash map. One is in coordinator
(GroupMetadataManager), and another is in group (ModernGroup).
For the coordinator, it's in memory cache. When a coordinator starts, we
will recalculate it from metadata image in
`GroupMetadataManager#subscribeGroupToTopic`. When there is a new metadata
image, we recalculate changed topic hash.
For the group, the hash map is updated when we replay
`ConsumerGroupPartitionMetadataValue`. We will add a new field `hash` to
`TopicMetadata`. Although it still calls `TopicMetadata`, we only cares hash
value, so in the code, we only need to maintain `Map<String, Long>
subscribedTopicHash`.
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