Skip to content

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.

Members Public

Fix KafkaConsumer Is Not Safe for Multi-Threaded Access

Hitting ConcurrentModificationException: KafkaConsumer is not safe for multi-threaded access? Here's why the thread guard fires and the correct fix.

Members Public

Kafka "Connection to node -1 could not be established" — Fix

Fix Kafka's "Connection to node -1 (localhost/127.0.0.1:9092) could not be established. Broker may not be available" — the Docker advertised.listeners fix.

Members Public

Kafka Connect Task Threw an Uncaught and Unrecoverable Exception

Kafka Connect task killed with 'uncaught and unrecoverable exception'? It's usually a converter poison pill. Here's the DataException root cause, DLQ fix, and design.

Members Public

Kafka Connect Failed to Flush: Offset Commit Timeout Fix

Kafka Connect source task logs 'Failed to flush, timed out while waiting for producer to flush outstanding N messages'. Here's the real cause and the fix.

Members Public

Kafka Connect: Failed to Find Any Class That Implements Connector

Kafka Connect throws 'Failed to find any class that implements Connector' when plugin.path is wrong or classloader isolation hides your JAR. Here's the fix.

Members Public

Kafka SerializationException: Can't Convert Value of Class Fix

Kafka SerializationException: Can't convert value of class X to StringSerializer? The ClassCastException behind it, the config fix, and the safer design.

Members Public

Kafka: Cannot Perform Operation After Producer Closed

Kafka IllegalStateException 'Cannot perform operation after producer has been closed' explained: why it happens, the Spring share

Members Public

Kafka BufferExhaustedException: Fix Failed to Allocate Memory

Kafka producer throws BufferExhaustedException: failed to allocate memory within max blocking time? Here's why buffer.memory fills up and the exact fix.

Members Public

Kafka "Connection to node -1 could not be established" — Fix

Fix Kafka's "Connection to node -1 (localhost/127.0.0.1:9092) could not be established. Broker may not be available" — the Docker advertised.listeners fix.

Members Public

Kafka SerializationException: Fixing Poison Pill Records

Kafka SerializationException: "Error deserializing key/value" crashes your consumer in a loop. Fix it with ErrorHandlingDeserializer and a dead letter topic.