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https://issues.apache.org/jira/browse/KAFKA-19785?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18042713#comment-18042713
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David commented on KAFKA-19785:
-------------------------------
After reviewing the issue, I identified a section that might be contributing to
the problem.
*Potentially related code:*
In {{raft/src/main/java/org/apache/kafka/raft/KafkaRaftClient.java}}, function
{{maybeTransition}} ([line
2525|https://github.com/apache/kafka/blob/985bc99521dd22bbf620591b8db8613c54f596b2/raft/src/main/java/org/apache/kafka/raft/KafkaRaftClient.java#L2525]):
The condition
{code:java}
if (!hasConsistentLeader(epoch, leaderId)) return;
{code}
is too strict. For the first valid leader discovery (currentLeader empty, epoch
matches), {{hasConsistentLeader}} returns false, causing the code path that
leads to an {{IllegalStateException}} at line 2526, fencing the broker.
*Possible fix:*
{code}
--- raft/src/main/java/org/apache/kafka/raft/KafkaRaftClient.java
+++ raft/src/main/java/org/apache/kafka/raft/KafkaRaftClient.java
@@ -2521,7 +2521,13 @@ private void maybeTransition(
OptionalInt leaderId,
int epoch,
Endpoints leaderEndpoints,
long currentTimeMs
) {
- if (!hasConsistentLeader(epoch, leaderId))
- return;
+ // Permit initial leader discovery: same epoch, but no current leader
set.
+ if (!hasConsistentLeader(epoch, leaderId)) {
+ if (currentLeader.isEmpty() && leaderId.isPresent() && epoch ==
currentEpoch) {
+ // first-time leader assignment; proceed to transition logic
+ } else {
+ return;
+ }
+ }
// Existing logic to apply state transition...
}
{code}
Please let me know if this assessment aligns with your understanding.
> Two Kafka brokers were not active in 3 node cluster setup
> ---------------------------------------------------------
>
> Key: KAFKA-19785
> URL: https://issues.apache.org/jira/browse/KAFKA-19785
> Project: Kafka
> Issue Type: Bug
> Affects Versions: 4.0.0
> Reporter: Sravani
> Priority: Major
>
> Hi Team,
> We were facing kafka issue where two of the kafka brokers were fenced and
> Kafka was not able to process messages. We are using Kafka 4.0.0 version.
> Below are the errors.
>
> Sep 22 09:41:42 s99ossv152 kafka[42245]: [2025-09-22 07:41:42,419] ERROR
> Encountered fatal fault: Unexpected error in raft IO thread
> (org.apache.kafka.server.fault.ProcessTerminatingFaultHandler)
> Sep 22 09:41:42 s99ossv152 kafka[42245]: java.lang.IllegalStateException:
> Received request or response with leader OptionalInt[3] and epoch 55 *which
> is inconsistent with current leader* OptionalInt.empty and epoch 55
> Sep 22 09:41:42 s99ossv152 kafka[42245]: #011at
> org.apache.kafka.raft.KafkaRaftClient.maybeTransition(KafkaRaftClient.java:2528)
> ~[kafka-raft-4.0.0.jar:?]
> Sep 22 09:41:42 s99ossv152 kafka[42245]: #011at
> org.apache.kafka.raft.KafkaRaftClient.maybeHandleCommonResponse(KafkaRaftClient.java:2484)
> ~[kafka-raft-4.0.0.jar:?]
> Sep 22 09:41:42 s99ossv152 kafka[42245]: #011at
> org.apache.kafka.raft.KafkaRaftClient.handleFetchResponse(KafkaRaftClient.java:1707)
> ~[kafka-raft-4.0.0.jar:?]
> Sep 22 09:41:42 s99ossv152 kafka[42245]: #011at
> org.apache.kafka.raft.KafkaRaftClient.handleResponse(KafkaRaftClient.java:2568)
> ~[kafka-raft-4.0.0.jar:?]
> Sep 22 09:41:42 s99ossv152 kafka[42245]: #011at
> org.apache.kafka.raft.KafkaRaftClient.handleInboundMessage(KafkaRaftClient.java:2724)
> ~[kafka-raft-4.0.0.jar:?]
> Sep 22 09:41:42 s99ossv152 kafka[42245]: #011at
> org.apache.kafka.raft.KafkaRaftClient.poll(KafkaRaftClient.java:3460)
> ~[kafka-raft-4.0.0.jar:?]
> Sep 22 09:41:42 s99ossv152 kafka[42245]: #011at
> org.apache.kafka.raft.KafkaRaftClientDriver.doWork(KafkaRaftClientDriver.java:64)
> [kafka-raft-4.0.0.jar:?]
> Sep 22 09:41:42 s99ossv152 kafka[42245]: #011at
> org.apache.kafka.server.util.ShutdownableThread.run(ShutdownableThread.java:136)
> [kafka-server-common-4.0.0.jar:?]
> Below metrics shows Fenceborker count as 2.0
> kafka_controller_KafkaController_Value\{name="ActiveBrokerCount",} 1.0
> kafka_controller_KafkaController_Value\{name="GlobalTopicCount",} 23.0
> kafka_controller_KafkaController_Value{name="{*}FencedBrokerCount{*}",} 2.0
> Please help us to resolve this issue.
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