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Gopi Gorantala

I'm Gopi — 15+ years in Java, building Kafka and Flink platforms for banks, where one lost event is a financial discrepancy. I write javahandbook.com because the guides I needed didn't exist. Everything here is tested against a real cluster first.

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Kafka RetriableCommitFailedException: Causes and Fix

Kafka RetriableCommitFailedException on offset commit means a transient commit failure you must retry yourself. Here's what triggers it and how to handle it correctly.

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Kafka: Assignments Can Only Be Reset If the Group Is Inactive

Kafka's reset-offsets fails with 'Assignments can only be reset if the group is inactive, but the current state is Stable.' Here's why, and the fix.

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Kafka RecordTooLargeException: The 1MB Limit and How to Fix It

Hitting RecordTooLargeException in Kafka? Learn why the 1MB default bites on both producer and broker, and the exact configs to fix it properly.

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Kafka RebalanceInProgressException: Why It Happens and How to Fix It

Kafka RebalanceInProgressException on commitSync/commitAsync with CooperativeStickyAssignor? Here's why it's not CommitFailedException, and the correct fix.

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Kafka ProducerFencedException: Why It Happens and How to Fix It

ProducerFencedException: there is a newer producer with the same transactionalId. What fences a Kafka transactional producer and the exact fix, explained.

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Kafka OffsetOutOfRangeException: auto.offset.reset Explained

Fix OffsetOutOfRangeException and NoOffsetForPartitionException in Kafka: why committed offsets vanish, what auto.offset.reset really does, and safe resets.

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Kafka NotLeaderOrFollowerException: Cause and Fix

Producer or consumer failing with NotLeaderOrFollowerException (NOT_LEADER_OR_FOLLOWER)? Why stale leader metadata causes it and how to fix it for good.

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Kafka NotEnoughReplicasException: Fix NOT_ENOUGH_REPLICAS Errors

Kafka NotEnoughReplicasException: messages rejected since there are fewer in-sync replicas than required. Fix min.insync.replicas vs acks=all, fast.

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Kafka NotControllerException: Why It Happens and How to Fix It

Kafka throws NotControllerException (code 41) when an admin request hits a broker that isn't the active controller. Here's the mechanism and the real fix.

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Kafka IllegalStateException: No Current Assignment for Partition

Getting java.lang.IllegalStateException: No current assignment for partition on seek()? Why Kafka's lazy assignment causes it — and the correct fix.