[GitHub] [kafka] rajinisivaram commented on a change in pull request #9382: KAFKA-10554; Perform follower truncation based on diverging epochs in Fetch response

[GitBox <gi...@apache.org>]

rajinisivaram commented on a change in pull request #9382:
URL: https://github.com/apache/kafka/pull/9382#discussion_r518198753



##########
File path: core/src/main/scala/kafka/server/AbstractFetcherThread.scala
##########
@@ -426,21 +451,34 @@ abstract class AbstractFetcherThread(name: String,
     warn(s"Partition $topicPartition marked as failed")
   }
 
-  def addPartitions(initialFetchStates: Map[TopicPartition, OffsetAndEpoch]): Set[TopicPartition] = {
+  /**
+   * Returns initial partition fetch state based on current state and the provided `initialFetchState`.
+   * From IBP 2.7 onwards, we can rely on truncation based on diverging data returned in fetch responses.
+   * For older versions, we can skip the truncation step iff the leader epoch matches the existing epoch.
+   */
+  private def partitionFetchState(tp: TopicPartition, initialFetchState: InitialFetchState, currentState: PartitionFetchState): PartitionFetchState = {
+    if (currentState != null && currentState.currentLeaderEpoch == initialFetchState.currentLeaderEpoch) {
+      currentState
+    } else if (isTruncationOnFetchSupported && initialFetchState.initOffset >= 0 && initialFetchState.lastFetchedEpoch.nonEmpty &&
+              (currentState == null || currentState.state == Fetching)) {
+      PartitionFetchState(initialFetchState.initOffset, None, initialFetchState.currentLeaderEpoch,
+          state = Fetching, initialFetchState.lastFetchedEpoch)

Review comment:
       I couldn't come up with a case where `currentState` is non-null, so I removed that check. Haven't seen any test failures as a result, so hopefully that is ok. 




----------------------------------------------------------------
This is an automated message from the Apache Git Service.
To respond to the message, please log on to GitHub and use the
URL above to go to the specific comment.

For queries about this service, please contact Infrastructure at:
users@infra.apache.org