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Quafka Development Progress

Last Updated: January 6, 2026
Current Focus: Consumer Group Sarama Integration

📊 Session Tracking

Current Session Goals

  • Write consumer group integration test using Sarama ConsumerGroup API
  • Fix protocol encoding issues discovered during testing
  • Get consumer group test to pass ✅ DONE!

✅ Completed Work

Protocol Fixes (Jan 6, 2026)

Fix File Description
MetadataResponse v2+ protocol/metadata_response.go Added ClusterID nullable string field
JoinGroupResponse protocol/join_group_response.go Fixed ThrottleTime to encode only for v2+ (was v1+)
OffsetFetchResponse protocol/offset_fetch_response.go Fixed Offset type from int16 to int64
OffsetFetchResponse v2+ protocol/offset_fetch_response.go Added trailing ErrorCode field
HeartbeatResponse v1+ protocol/heartbeat_response.go Added ThrottleTime encoding
API Versions protocol/api_versions.go Added OffsetCommitKey and OffsetFetchKey
OffsetCommitRequest protocol/offset_commit_request.go Fixed missing Topic field, version-specific fields, range iteration

Consumer Group Handler Fixes (Jan 6, 2026)

Fix File Description
State Transition quafka/broker.go handleJoinGroup now transitions to CompletingRebalance
GroupProtocol quafka/broker.go handleJoinGroup now sets GroupProtocol in response
Leader Assignment quafka/broker.go handleSyncGroup now returns leader's assignment (was nil)
OffsetFetch Error Response quafka/broker.go Returns all requested partitions with error codes instead of empty
Offsets Topic Replicas quafka/broker.go offsetsTopic() now starts replicas via LeaderAndISR
Offsets Partitions Config quafka/config/config.go Added OffsetsTopicNumPartitions config option

Test Infrastructure (Jan 6, 2026)

  • Created TestConsumerGroup in quafka/server_test.go
  • Created TestConsumerGroupOffsetPersistence to test sequential consumer groups
  • Reduced OffsetsTopicReplicationFactor to 1 for single-node tests
  • Reduced OffsetsTopicNumPartitions to 10 for faster test startup
  • TestConsumerGroup now PASSES ✅
  • All integration tests pass ✅

Prior Work (Before Jan 6)

  • Kafka client compatibility fixes (MetadataRequest/Response)
  • Decoder array length handling for -1 (null arrays)
  • BuildIndex bug fix in commitlog
  • Package rename from jocko to quafka
  • Consumer group PR merge with conflict resolution
  • FEATURES.md checklist creation
  • CI optimization for faster feedback

🔧 Pending Work

High Priority - Consumer Group Test ✅ RESOLVED

Issue 1: Replica Timing ✅ FIXED

Solution:

  1. Added OffsetsTopicNumPartitions config option (default 50, tests use 10)
  2. Modified offsetsTopic() to call LeaderAndISR after creating partitions
  3. Replicas are now started synchronously before FindCoordinator returns

Issue 2: Empty OffsetFetch Response ✅ FIXED

Solution: Modified handleOffsetFetch to return all requested partitions with ErrCoordinatorLoadInProgress or ErrNotCoordinator error codes instead of empty response.

Issue 3: Consumer Never Starts Fetching ✅ FIXED

Root Cause: Issues 1 and 2 combined - replicas not ready + empty response = Sarama gave up Resolution: With Issues 1 & 2 fixed, Sarama now successfully transitions to consuming phase.

Medium Priority

OffsetCommit Decoding Issue ✅ FIXED

Solution: Fixed protocol/offset_commit_request.go:

  • Added missing Topic string field decode
  • Fixed range iteration to use index instead of value copies
  • Added proper version-specific field handling (GenerationID, MemberID, RetentionTime, Timestamp)

OffsetCommit Testing

  • Verify offset commits are stored correctly in __consumer_offsets
  • Test offset persistence across consumer restarts

Low Priority

TestProduceConsume Flakiness (Improved but not fully fixed)

Issue: Multi-node test sometimes times out waiting for leader election after failover Current Fix: Added retry logic around produce and consume operations Remaining Issue: RetryFunc 7-second timeout may not be enough in some cases Potential Fixes:

  • Increase RetryFunc timeout for failover scenarios
  • Add explicit partition leader check before operations
  • Improve Raft leader election timing

Performance

  • Consider reducing offsets topic partitions ✅ Done - configurable via OffsetsTopicNumPartitions
  • Optimize replica creation for faster test startup ✅ Done - replicas started in offsetsTopic()

📁 Key Files Reference

Protocol Files

  • protocol/metadata_response.go - Metadata API
  • protocol/join_group_response.go - JoinGroup API
  • protocol/sync_group_response.go - SyncGroup API
  • protocol/offset_fetch_response.go - OffsetFetch API
  • protocol/heartbeat_response.go - Heartbeat API
  • protocol/api_versions.go - Advertised API versions

Handler Files

  • quafka/broker.go - All request handlers (handleJoinGroup, handleSyncGroup, etc.)
  • quafka/offsets.go - Offset commit/fetch encoding structures

Test Files

  • quafka/server_test.go - Integration tests including TestConsumerGroup
  • quafka/consumer_group_test.go - Unit tests for consumer group

🧪 Test Commands

# Run consumer group integration test
go test -v -timeout 90s -run TestConsumerGroup ./quafka/

# Run basic produce/consume test (known working)
go test -v -timeout 60s -run TestProduceConsume ./quafka/

# Run all short tests
go test -short ./...

# Run with verbose logging
QUAFKADEBUG=1 go test -v -run TestConsumerGroup ./quafka/

📝 Notes for Future Sessions

  1. Consumer Group Flow: FindCoordinator → JoinGroup → Metadata → SyncGroup → OffsetFetch → Heartbeat → Fetch ✅ Working!
  2. Sarama Version: Using V0_10_2_0 which requires consumer group support
  3. TestConsumerGroup PASSES - Consumer group integration with Sarama is working
  4. Basic produce/consume with Sarama works - confirms protocol fixes are sound
  5. QSE-Service compatibility: Protocol changes don't affect commitlog direct usage
  6. OffsetCommit decoding: ✅ Fixed - OffsetCommit requests now decode and process correctly

🔗 Related Documents

  • FEATURES.md - Feature checklist comparing Quafka vs Kafka
  • CHANGELOG.md - Version history and changes
  • README.md - Project overview

This file tracks development progress. Update after each session.