CRITICAL FIX: Implement proper JoinGroup request parsing and consumer subscription extraction
## Issues Fixed:
- JoinGroup was ignoring protocol type and group protocols from requests
- Consumer subscription extraction was hardcoded to 'test-topic'
- Protocol metadata parsing was completely stubbed out
- Group instance ID for static membership was not parsed
## JoinGroup Request Parsing:
- Parse Protocol Type (string) - validates consumer vs producer protocols
- Parse Group Protocols array with:
- Protocol name (range, roundrobin, sticky, etc.)
- Protocol metadata (consumer subscriptions, user data)
- Parse Group Instance ID (nullable string) for static membership (Kafka 2.3+)
- Added comprehensive debug logging for all parsed fields
## Consumer Subscription Extraction:
- Implement proper consumer protocol metadata parsing:
- Version (2 bytes) - protocol version
- Topics array (4 bytes count + topic names) - actual subscriptions
- User data (4 bytes length + data) - client metadata
- Support for multiple assignment strategies (range, roundrobin, sticky)
- Fallback to 'test-topic' only if parsing fails
- Added detailed debug logging for subscription extraction
## Protocol Compliance:
- Follows Kafka JoinGroup protocol specification
- Proper handling of consumer protocol metadata format
- Support for static membership (group instance ID)
- Robust error handling for malformed requests
## Testing:
- Compilation successful
- Debug logging will show actual parsed protocols and subscriptions
- Should enable real consumer group coordination with proper topic assignments
This fix resolves the third critical compatibility issue preventing
real Kafka consumers from joining groups and getting correct partition assignments.
chrislu
e2722045a4