Kafka Error INVALID_FETCH_SIZE
Error code 4 · Non-retriable Consumer
The requested fetch size is invalid.
Common Causes
- Consumer 'fetch.max.bytes' or 'max.partition.fetch.bytes' set to 0 or a negative value, causing the broker to reject the fetch request
- Buggy custom client or third-party library sending a malformed FetchRequest with an invalid fetch size field
- Application code dynamically overriding consumer properties with an invalid computed value (e.g. calculating fetch size from a formula that yields 0 or negative)
Solutions
- Set 'fetch.max.bytes' to a valid positive integer (default is 52428800 = 50MB); ensure 'max.partition.fetch.bytes' (default 1MB) is at least as large as the largest expected message
- Align fetch size settings: fetch.max.bytes >= max.partition.fetch.bytes >= message.max.bytes (broker) to avoid cascading fetch rejections
- Audit consumer configuration at startup by logging all consumer properties before the first poll() call to catch typos or override bugs
Diagnostic Commands
# Check consumer fetch configuration
grep -E 'fetch.max.bytes|max.partition.fetch.bytes' <consumer-config-file>
# Describe consumer group offsets and lag
kafka-consumer-groups.sh --bootstrap-server localhost:9092 --group <group> --describe
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