FrankYang0529 commented on code in PR #19761:
URL: https://github.com/apache/kafka/pull/19761#discussion_r2107213749
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group-coordinator/src/main/java/org/apache/kafka/coordinator/group/Utils.java:
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@@ -349,12 +349,19 @@ static void throwIfRegularExpressionIsInvalid(
* @return The hash of the group.
*/
static long computeGroupHash(Map<String, Long> topicHashes) {
- if (topicHashes.isEmpty()) {
+ // Sort entries by topic name
+ List<Map.Entry<String, Long>> sortedEntries = new ArrayList<>();
+ for (Map.Entry<String, Long> entry : topicHashes.entrySet()) {
+ // Filter out entries with a hash value of 0, which indicates no
topic
+ if (entry.getValue() != 0) {
Review Comment:
We use `computeSubscribedTopicNames` to get `subscribedTopicNames` and use
the result to calculate topic hashes which group wants to subscribe to.
However, the `computeSubscribedTopicNames` doesn't check whether a topic is
really existent. If a group subscribes to a non-existent topic, the topic is in
`subscribedTopicNames` and the `computeMetadataHash` uses non-existent topic
hash as part of metadata hash.
A sample case is `testSubscriptionMetadataRefreshedAgainAfterWriteFailure`.
The group subscribes to `foo` and `bar`, but `bar` topic is not in metadata
image.
https://github.com/apache/kafka/blob/48a52701b9cd45c4854f910990a85be7d73e22f5/group-coordinator/src/main/java/org/apache/kafka/coordinator/group/modern/ModernGroup.java#L496-L507
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