# CommitFailedError: Commit cannot be completed since the group has already rebalanced and assigned the partitions to another member

- **ID:** `communication/kafka-consumer-commit-failed-rebalance`
- **Domain:** communication
- **Category:** runtime_error
- **Verification:** ai_generated
- **Fix Rate:** 85%

## Root Cause

Kafka consumer attempted to commit offsets after a group rebalance had already occurred, often because processing time exceeded `max.poll.interval.ms`, causing the consumer to be removed from the group.

## Version Compatibility

| Version | Status | Introduced | Deprecated |
|---------|--------|------------|------------|
| Apache Kafka 3.4 | active | — | — |
| Kafka 3.6 | active | — | — |
| confluent-kafka-python 2.3 | active | — | — |
| spring-kafka 3.0 | active | — | — |

## Workarounds

1. **Increase `max.poll.interval.ms` to a value higher than the expected maximum processing time, e.g., `max.poll.interval.ms=600000` (10 minutes) in consumer config.** (90% success)
   ```
   Increase `max.poll.interval.ms` to a value higher than the expected maximum processing time, e.g., `max.poll.interval.ms=600000` (10 minutes) in consumer config.
   ```
2. **Reduce processing time per poll by using asynchronous processing: fetch records, process in a separate thread pool, and commit offsets only after all processing completes, e.g., using `KafkaConsumer` with `enable.auto.commit=false` and manual async commits.** (85% success)
   ```
   Reduce processing time per poll by using asynchronous processing: fetch records, process in a separate thread pool, and commit offsets only after all processing completes, e.g., using `KafkaConsumer` with `enable.auto.commit=false` and manual async commits.
   ```
3. **Implement cooperative rebalancing (incremental rebalance protocol) by setting `partition.assignment.strategy=CooperativeStickyAssignor`, which allows consumers to retain some partitions during rebalance.** (80% success)
   ```
   Implement cooperative rebalancing (incremental rebalance protocol) by setting `partition.assignment.strategy=CooperativeStickyAssignor`, which allows consumers to retain some partitions during rebalance.
   ```

## Dead Ends

- **Increase `max.poll.records` to process more records per poll and reduce polling frequency** — Processing more records per poll increases processing time, exacerbating the rebalance issue. (75% fail)
- **Disable auto-commit and commit offsets manually after every single record** — Frequent commits increase load and may still fail if a rebalance occurs between commits. (65% fail)
- **Set `session.timeout.ms` to a very low value to detect failures faster** — This can cause unnecessary rebalances if consumers are healthy but take slightly longer to poll. (80% fail)