bozhao12 commented on a change in pull request #11965:
URL: https://github.com/apache/kafka/pull/11965#discussion_r838290447
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File path: core/src/test/scala/unit/kafka/server/ReplicaManagerTest.scala
##########
@@ -1300,6 +1300,62 @@ class ReplicaManagerTest {
TestUtils.assertNoNonDaemonThreads(this.getClass.getName)
}
+ @Test
+ def testFollowerShouldNotExecutePreferLeaderSelect(): Unit = {
+ val replicaManager = setupReplicaManagerWithMockedPurgatories(new
MockTimer(time), aliveBrokerIds = Seq(0, 1, 2),
+ propsModifier = props => props.put(KafkaConfig.ReplicaSelectorClassProp,
"org.apache.kafka.common.replica.RackAwareReplicaSelector"))
+ try {
+ val leaderBrokerId = 0
+ val follower1BrokerId = 1
+ val follower2BrokerId = 2
+ val brokerList = Seq[Integer](leaderBrokerId, follower1BrokerId,
follower2BrokerId).asJava
+ val topicId = Uuid.randomUuid()
+ val tp0 = new TopicPartition(topic, 0)
+ val tidp0 = new TopicIdPartition(topicId, tp0)
+ initializeLogAndTopicId(replicaManager, tp0, topicId)
+ when(replicaManager.metadataCache.getPartitionReplicaEndpoints(
+ tp0,
+ new ListenerName("default")
+ )).thenReturn(Map(
+ leaderBrokerId -> new Node(leaderBrokerId, "host1", 9092, "rack-a"),
+ follower1BrokerId -> new Node(follower1BrokerId, "host2", 9092,
"rack-a"),
+ follower2BrokerId -> new Node(follower2BrokerId, "host3", 9092,
"rack-b")
+ ).toMap)
+
+ // Make this replica the follower
+ val leaderAndIsrRequest = new
LeaderAndIsrRequest.Builder(ApiKeys.LEADER_AND_ISR.latestVersion, 0, 0,
brokerEpoch,
+ Seq(new LeaderAndIsrPartitionState()
+ .setTopicName(topic)
+ .setPartitionIndex(0)
+ .setControllerEpoch(0)
+ .setLeader(2)
+ .setLeaderEpoch(1)
+ .setIsr(brokerList)
+ .setZkVersion(0)
+ .setReplicas(brokerList)
+ .setIsNew(false)).asJava,
+ Collections.singletonMap(topic, topicId),
+ Set(new Node(0, "host1", 0), new Node(1, "host2", 1), new Node(2,
"host3", 1)).asJava).build()
+ replicaManager.becomeLeaderOrFollower(1, leaderAndIsrRequest, (_, _) =>
())
+ // Avoid the replica selector ignore the follower replica if it not have
the data that need to fetch
+
replicaManager.getPartitionOrException(tp0).updateFollowerFetchState(follower1BrokerId,
+ new LogOffsetMetadata(0), 0, 0, 0)
Review comment:
@dajac If this line is removed, the test still passes, because the
preferred read replica selected by the follower broker is the leader node, and
`findPreferredReadReplica() `method will eventually return None.
I want to prove through this case that if just the change in
`findPreferredReadReplica() `is removed, in the current situation, follower
will also execute the preferred read replica selection and can success select
the replica, The unit test will failed.
Another key problem is that we only want the leader broker to perform the
preferred read replica election, but in fact, the follower can also perform the
election.
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