dajac commented on code in PR #16898:
URL: https://github.com/apache/kafka/pull/16898#discussion_r1721533978
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group-coordinator/src/main/java/org/apache/kafka/coordinator/group/GroupMetadataManager.java:
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@@ -848,26 +844,32 @@ ConsumerGroup consumerGroup(
ConsumerGroup getOrMaybeCreatePersistedConsumerGroup(
String groupId,
boolean createIfNotExists
- ) throws GroupIdNotFoundException {
+ ) throws IllegalStateException {
Group group = groups.get(groupId);
if (group == null && !createIfNotExists) {
- throw new IllegalStateException(String.format("Consumer group %s
not found.", groupId));
+ throw new IllegalStateException(String.format("Consumer group %s
not found", groupId));
}
if (group == null) {
ConsumerGroup consumerGroup = new ConsumerGroup(snapshotRegistry,
groupId, metrics);
groups.put(groupId, consumerGroup);
metrics.onConsumerGroupStateTransition(null,
consumerGroup.state());
return consumerGroup;
+ } else if (group.type() == CONSUMER) {
+ return (ConsumerGroup) group;
+ } else if (group.type() == CLASSIC && ((ClassicGroup)
group).isSimpleGroup()) {
+ // If the group is a simple classic group, it was automatically
created to hold committed
+ // offsets if no group existed. Simple classic groups are not
backed by any records
+ // in the __consumer_offsets topic hence we can safely replace it
here. Without this,
+ // replaying consumer group records after offset commit records
would not work.
Review Comment:
The issue happens when the offset commit records are before the consumer
group records in the log (e.g. after compaction). When replaying, the following
happens:
* OOM#replay will create a simple classic group if the group does not exist.
* GMM#replay for consumer group records fails because a classic group always
exists.
This change handle the case in GMM#replay to basically swap the group if the
group was a simple classic group.
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