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[aiven] workaround to randomize remote fetch partition #52

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27 changes: 24 additions & 3 deletions core/src/main/scala/kafka/server/ReplicaManager.scala
Original file line number Diff line number Diff line change
Expand Up @@ -71,6 +71,7 @@ import java.util.{Optional, OptionalInt, OptionalLong}
import scala.collection.{Map, Seq, Set, mutable}
import scala.compat.java8.OptionConverters._
import scala.jdk.CollectionConverters._
import scala.util.Random

/*
* Result metadata of a log append operation on the log
Expand Down Expand Up @@ -1646,7 +1647,9 @@ class ReplicaManager(val config: KafkaConfig,
var errorReadingData = false

// The 1st topic-partition that has to be read from remote storage
var remoteFetchInfo: Optional[RemoteStorageFetchInfo] = Optional.empty()
// WORKAROUND: randomize partition fetched
// var remoteFetchInfo: Optional[RemoteStorageFetchInfo] = Optional.empty()
var remoteFetchInfos: Seq[Optional[RemoteStorageFetchInfo]] = Seq.empty

var hasDivergingEpoch = false
var hasPreferredReadReplica = false
Expand All @@ -1657,8 +1660,12 @@ class ReplicaManager(val config: KafkaConfig,
brokerTopicStats.allTopicsStats.totalFetchRequestRate.mark()
if (logReadResult.error != Errors.NONE)
errorReadingData = true
if (!remoteFetchInfo.isPresent && logReadResult.info.delayedRemoteStorageFetch.isPresent) {
remoteFetchInfo = logReadResult.info.delayedRemoteStorageFetch
// WORKAROUND: randomize partition fetched
//if (!remoteFetchInfo.isPresent && logReadResult.info.delayedRemoteStorageFetch.isPresent) {
// remoteFetchInfo = logReadResult.info.delayedRemoteStorageFetch
//}
if (logReadResult.info.delayedRemoteStorageFetch.isPresent) {
remoteFetchInfos = remoteFetchInfos ++ Seq(logReadResult.info.delayedRemoteStorageFetch)
}
if (logReadResult.divergingEpoch.nonEmpty)
hasDivergingEpoch = true
Expand All @@ -1668,6 +1675,8 @@ class ReplicaManager(val config: KafkaConfig,
logReadResultMap.put(topicIdPartition, logReadResult)
}

val remoteFetchInfo: Optional[RemoteStorageFetchInfo] = maybeRemoteFetchInfo(remoteFetchInfos)

// Respond immediately if no remote fetches are required and any of the below conditions is true
// 1) fetch request does not want to wait
// 2) fetch request does not require any data
Expand Down Expand Up @@ -1723,6 +1732,18 @@ class ReplicaManager(val config: KafkaConfig,
}
}

// WORKAROUND: randomize partition fetched
private val rnd = new Random()
def maybeRemoteFetchInfo(remoteFetchInfos: Seq[Optional[RemoteStorageFetchInfo]]): Optional[RemoteStorageFetchInfo] = {
val remoteFetchInfo: Optional[RemoteStorageFetchInfo] = if (remoteFetchInfos.isEmpty) {
Optional.empty()
} else {
val i = rnd.nextInt(remoteFetchInfos.size)
remoteFetchInfos(i)
}
remoteFetchInfo
}

/**
* Read from multiple topic partitions at the given offset up to maxSize bytes
*/
Expand Down
45 changes: 45 additions & 0 deletions core/src/test/scala/unit/kafka/server/ReplicaManagerTest.scala
Original file line number Diff line number Diff line change
Expand Up @@ -6558,6 +6558,51 @@ class ReplicaManagerTest {
))
}
}

@Test
def testRandomizedRemoteFetchInfo(): Unit = {
// Given
val props = TestUtils.createBrokerConfig(1, TestUtils.MockZkConnect, logDirCount = 2)
val config = KafkaConfig.fromProps(props)
val logDirFiles = config.logDirs.map(new File(_))
val logDirFailureChannel = new LogDirFailureChannel(config.logDirs.size)
val logManager = TestUtils.createLogManager(logDirFiles, defaultConfig = new LogConfig(new Properties()), time = time)
val mockZkClient = mock(classOf[KafkaZkClient])
val replicaManager = new ReplicaManager(
metrics = metrics,
config = config,
time = time,
scheduler = time.scheduler,
logManager = logManager,
quotaManagers = quotaManager,
metadataCache = MetadataCache.zkMetadataCache(config.brokerId, config.interBrokerProtocolVersion),
logDirFailureChannel = logDirFailureChannel,
alterPartitionManager = alterPartitionManager,
threadNamePrefix = Option(this.getClass.getName),
zkClient = Option(mockZkClient),
)

var infos: Seq[Optional[RemoteStorageFetchInfo]] = Seq()

// When
val emptyRemoteFetchInfo = replicaManager.maybeRemoteFetchInfo(infos)

// Then
assertFalse(emptyRemoteFetchInfo.isPresent)

// Given
val info0 = new RemoteStorageFetchInfo(1000, false, new TopicPartition(topic, 0), null, FetchIsolation.HIGH_WATERMARK, false)
val info1 = new RemoteStorageFetchInfo(1000, false, new TopicPartition(topic, 1), null, FetchIsolation.HIGH_WATERMARK, false)
val info2 = new RemoteStorageFetchInfo(1000, false, new TopicPartition(topic, 2), null, FetchIsolation.HIGH_WATERMARK, false)
infos = infos ++ Seq(Optional.of(info0), Optional.of(info1), Optional.of(info2))

// When
val someRemoteFetchInfo = replicaManager.maybeRemoteFetchInfo(infos)

// Then
assertTrue(someRemoteFetchInfo.isPresent)
println(someRemoteFetchInfo.get())
}
}

class MockReplicaSelector extends ReplicaSelector {
Expand Down
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