[GitHub] [kafka] dajac commented on a diff in pull request #14053: [KAFKA-15221] Fix the race between fetch requests from a rebooted follower.

[via GitHub]

dajac commented on code in PR #14053:
URL: https://github.com/apache/kafka/pull/14053#discussion_r1269075133


##########
core/src/main/scala/kafka/cluster/Replica.scala:
##########
@@ -98,31 +101,39 @@ class Replica(val brokerId: Int, val topicPartition: 
TopicPartition) extends Log
    * fetch request is always smaller than the leader's LEO, which can happen 
if small produce requests are received at
    * high frequency.
    */
-  def updateFetchState(
+  def maybeUpdateFetchState(
     followerFetchOffsetMetadata: LogOffsetMetadata,
     followerStartOffset: Long,
     followerFetchTimeMs: Long,
     leaderEndOffset: Long,
     brokerEpoch: Long
-  ): Unit = {
+  ): Boolean = {
+    var updateSuccess = true
     replicaState.updateAndGet { currentReplicaState =>
-      val lastCaughtUpTime = if (followerFetchOffsetMetadata.messageOffset >= 
leaderEndOffset) {
-        math.max(currentReplicaState.lastCaughtUpTimeMs, followerFetchTimeMs)
-      } else if (followerFetchOffsetMetadata.messageOffset >= 
currentReplicaState.lastFetchLeaderLogEndOffset) {
-        math.max(currentReplicaState.lastCaughtUpTimeMs, 
currentReplicaState.lastFetchTimeMs)
+      // Fence the update if it provides a stale broker epoch.
+      if (brokerEpoch != -1 && brokerEpoch < 
currentReplicaState.brokerEpoch.getOrElse(-1L)) {
+        updateSuccess = false

Review Comment:
   It is not recommended to have side effect in the method updating the state 
of an atomic value. I wonder if we could throw an exception instead to really 
ensure that the update process is stopped.



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