cmccabe commented on code in PR #15810:
URL: https://github.com/apache/kafka/pull/15810#discussion_r1586861400
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metadata/src/main/java/org/apache/kafka/controller/PartitionChangeBuilder.java:
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@@ -365,45 +369,62 @@ private void tryElection(PartitionChangeRecord record) {
}
/**
- * Trigger a leader epoch bump if one is needed.
- *
- * We need to bump the leader epoch if:
- * 1. The leader changed, or
- * 2. The new replica list does not contain all the nodes that the old
replica list did.
- *
- * Changes that do NOT fall in any of these categories will increase the
partition epoch, but
- * not the leader epoch. Note that if the leader epoch increases, the
partition epoch will
- * always increase as well; there is no case where the partition epoch
increases more slowly
- * than the leader epoch.
+ * Trigger a leader epoch bump if one is needed because of replica
reassignment.
*
- * If the PartitionChangeRecord sets the leader field to something other
than
- * NO_LEADER_CHANGE, a leader epoch bump will automatically occur. That
takes care of
- * case 1. In this function, we check for cases 2 and 3, and handle them
by manually
- * setting record.leader to the current leader.
- *
- * In MV before 3.6 there was a bug (KAFKA-15021) in the brokers' replica
manager
- * that required that the leader epoch be bump whenever the ISR shrank. In
MV 3.6 this leader
- * bump is not required when the ISR shrinks. Note, that the leader epoch
is never increased if
- * the ISR expanded.
+ * Note that if the leader epoch increases, the partition epoch will
always increase as well; there is no
+ * case where the partition epoch increases more slowly than the leader
epoch.
+ */
+ void
triggerLeaderEpochBumpForReplicaReassignmentIfNeeded(PartitionChangeRecord
record) {
Review Comment:
I agree that the name should be revisited. Better to do that in a follow-on
PR, though, to avoid making this one too big.
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