dajac commented on code in PR #15785:
URL: https://github.com/apache/kafka/pull/15785#discussion_r1587222161
##########
group-coordinator/src/main/java/org/apache/kafka/coordinator/group/consumer/ConsumerGroup.java:
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@@ -966,6 +979,53 @@ private static void maybeUpdateSubscribedTopicNames(
}
}
+ /**
+ * Updates the subscription count.
+ *
+ * @param oldMember The old member.
+ * @param newMember The new member.
+ *
+ * @return Copy of the map of topics to the count of number of subscribers.
+ */
+ public Map<String, Integer> computeSubscribedTopicNames(
+ ConsumerGroupMember oldMember,
+ ConsumerGroupMember newMember
+ ) {
+ Map<String, Integer> subscribedTopicNames = new
HashMap<>(this.subscribedTopicNames);
+ maybeUpdateSubscribedTopicNames(
+ subscribedTopicNames,
+ oldMember,
+ newMember
+ );
+ return subscribedTopicNames;
+ }
+
+ /**
+ * Compute the subscription type of the consumer group.
+ *
+ * @param subscribedTopicNames A map of topic names to the count of
members subscribed to each topic.
+ *
+ * @return {@link SubscriptionType#HOMOGENEOUS} if all members are
subscribed to exactly the same topics;
+ * otherwise, {@link SubscriptionType#HETEROGENEOUS}.
+ */
+ public static SubscriptionType subscriptionType(
+ Map<String, Integer> subscribedTopicNames
+ ) {
+ if (subscribedTopicNames.isEmpty()) {
+ return HOMOGENEOUS;
+ }
+
+ // Take the subscriber count of the first topic as the reference.
+ int referenceCount = subscribedTopicNames.values().iterator().next();
Review Comment:
We don't allow subscribing with no topic names with the consumer protocol so
this logic works in this case. However, thinking about
https://github.com/apache/kafka/pull/15798, it may not be true when the classic
protocol is used to join a consumer group. @dongnuo123 Do you confirm?
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