ocadaruma commented on code in PR #12405:
URL: https://github.com/apache/kafka/pull/12405#discussion_r922801263
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core/src/main/scala/kafka/controller/ControllerContext.scala:
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@@ -328,8 +328,9 @@ class ControllerContext {
}
def queueTopicDeletion(topics: Set[String]): Unit = {
+ val newlyDeletedTopics = topics.diff(topicsToBeDeleted)
Review Comment:
(I'm not 100% sure if I get your concern. If my answer doesn't make sense,
please tell me)
In the first place, the purpose of `cleanPreferredReplicaImbalanceMetric` is
to "unmark" partitions which has imbalanced leader.
So, below is the expected behavior (let's say topic-A has single partition):
- Initiate topic-A deletion
- If topic-A-0 has imbalanced leader (e.g. lost leadership once,
replica-reassignment, became offline etc) here,
`preferredReplicaImbalanceCount` contains the count for it here, so we have to
decrement it because the partition is to be deleted
* `!hasPreferredLeader` evaluates to true so decremented as expected
- Otherwise, we don't have to decrement the value because
`preferredReplicaImbalanceCount` doesn't contain the imbalance count for
`topic-A-0`.
"A partition should be decremented from preferredReplicaImbalanceCount on
topic-deletion only if the partition is actually imbalanced at the
topic-deletion timing" is the invariant that topic-deletion procedure must
satisfy.
So, essentially, the problem is that topic-A-0 could be marked as
"imbalanced" wrongly when it becomes offline during deletion-procedure.
> So, what if the topic-A haven't reached this condition and we entering
cleanPreferredReplicaImbalanceMetric? Will that cause some partitions count
should be decremented but they are not?
"topic-A haven't reached this condition" means the partition wasn't
imbalanced actually, so we do not have to decrement the count.
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