[KAFKA-13767] Fetch from consumers should return immediately when preferred read replica is defined by the leader

• Type: Improvement
• Status: Resolved
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 2.4.0
• Fix Version/s: 3.2.0
• Component/s: core

Language

scala

• Assignee: zhaobo
• Reporter: zhaobo
• Reviewer: David Jacot
• Created: 24/Mar/22 06:46
• Updated: 21/Apr/22 06:57
• Resolved: 29/Mar/22 08:18

Description

 

def readFromLocalLog()
...

if (preferredReadReplica.isDefined) {
  ....
  // If a preferred read-replica is set, skip the read
  val offsetSnapshot = partition.fetchOffsetSnapshot(fetchInfo.currentLeaderEpoch, fetchOnlyFromLeader = false)
  LogReadResult(info = FetchDataInfo(LogOffsetMetadata.UnknownOffsetMetadata, MemoryRecords.EMPTY),
    divergingEpoch = None,
    ....
} 

 

when  a preferred read-replica is set, skip the read ,return empty data. The fetch request maybe put into the delayFetchQueue and repeat execute the readFromLocalLog() . It might be better to return the response right away.

Issue Links

• links to: GitHub Pull Request #11942