Kafka Error FETCH_SESSION_ID_NOT_FOUND
Error code 70 · Retriable Consumer
The fetch session ID was not found.
Common Causes
- Broker restarted or failover occurred, clearing in-memory incremental fetch session state (sessions are not persisted)
- Broker's fetch session cache was evicted due to memory pressure (`max.incremental.fetch.session.cache.slots` exceeded with many consumers)
- Consumer was redirected to a different broker (leader change) but sent a fetch request with the old session ID
Solutions
- This is retriable — the consumer will automatically create a new fetch session on the next request; no manual action needed unless it loops
- Increase `max.incremental.fetch.session.cache.slots` (default 1000) on brokers if fetch sessions are being evicted frequently under load
- Investigate frequent broker leader changes if this error appears repeatedly — stabilize the cluster to reduce session invalidation
Diagnostic Commands
# Look for fetch session events in logs
grep 'FetchSession\|FETCH_SESSION_ID_NOT_FOUND\|fetch.session' /path/to/kafka/logs/server.log | tail -20
# Check broker fetch session configuration
kafka-configs.sh --bootstrap-server localhost:9092 --entity-type brokers --entity-default --describe | grep fetch.sessionRelated APIs
This error can be returned by: Fetch
Debugging Kafka errors? Conduktor Console gives you real-time visibility into your cluster. Explore all errors in the Error Decoder.