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.

KafkaStorageException: Disk Error & No Space Left on Device

Fix org.apache.kafka.common.errors.KafkaStorageException and 'No space left on device' broker shutdowns — recovery runbook, retention math, disk sizing.

Kafka Streams MissingSourceTopicException: Fix It Fast

Kafka Streams dies with MissingSourceTopicException on startup or rebalance. Here's why the assignor flags a missing source topic and how to fix it.

Kafka SSL Handshake Failed: PKIX and Hostname Fixes

Fix org.apache.kafka.common.errors.SslAuthenticationException: SSL handshake failed — PKIX path errors, SAN mismatches, and listener protocol mixups fast.

Kafka SaslAuthenticationException: Authentication Failed — Fix

Getting SaslAuthenticationException: Authentication failed in Kafka? Fix invalid SASL credentials, JAAS config, and missing SCRAM users with working examples.

Kafka "Failed to construct kafka consumer": Every Cause, Fixed

KafkaException: Failed to construct kafka consumer — how to triage every common cause (deserializer class, classpath, DNS, JAAS, SSL) and fix each one fast.

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.

Kafka InvalidStateStoreException: State Store May Have Migrated

Fixing InvalidStateStoreException: "the state store may have migrated to another instance" in Kafka Streams — root causes, retry logic, and the right IQ design.

Kafka FETCH_SESSION_ID_NOT_FOUND: Causes and Fix

Kafka logs spamming FETCH_SESSION_ID_NOT_FOUND or INVALID_FETCH_SESSION_EPOCH? Here's what the fetch session cache is doing and how to stop the noise.

Schema Being Registered Is Incompatible: Kafka 409 Fix

Fix "Schema being registered is incompatible with an earlier schema; error code: 409" — why Schema Registry rejects your schema and how to evolve safely.

Kafka SerializationException: Schema Not Found (40403) Fix

Kafka consumer dies with SerializationException: Error retrieving Avro schema for id N, Schema not found; error code: 40403. Why the ID lookup fails and how to fix it.