v0.1.5 — io_uring Kernel Bypass & Latency Optimizations

What's New

StrikeMQ v0.1.5 brings sharded storage locks, circular I/O buffers, and an optional io_uring event loop on Linux — delivering measured 4.4μs p99.9 produce latency (log append path).

Performance (measured)

Metric	p50	p99.9
Log append 1KB	83 ns	4.4 μs
SPSC ring push+pop	—	42 ns
Pool alloc+free	—	42 ns
Kafka header decode	—	42 ns

New Features

• ShardedLogMap<64> — 64 cache-line-aligned shards replace the global logs_mu mutex. Concurrent Produce/Fetch/ListOffsets to different shards never contend on the same lock.

• FixedCircularBuffer — Power-of-2 ring buffer (128KB) replaces std::vector<uint8_t> for connection I/O. Monotonic head/tail counters with bitmask wrapping — all operations O(1). Eliminates erase(begin, begin+n) reallocation overhead.

• io_uring event loop (Linux, STRIKE_IO_URING) — Submission-based I/O with io_uring_prep_recv/io_uring_prep_send. Attempts SQPOLL first (kernel-side submission thread), falls back gracefully.

• MAP_POPULATE + pre-fault — Linux segment mmaps avoid TLB misses on initial writes. First 2MB of each new segment is pre-faulted.

• SO_BUSY_POLL — Optional busy-poll on accepted sockets (Linux) for reduced wakeup latency.

• 1ms event loop timeout — All event loops (kqueue, epoll, io_uring, acceptor) reduced from 100ms to 1ms.

• String hoisting in decode paths — One string copy per topic instead of per partition in Kafka protocol decoders.

New Config Fields

Parameter	Default	Description
busy_poll	false	Enable SO_BUSY_POLL on accepted sockets (Linux)
io_uring_sq_entries	256	io_uring submission queue size
io_uring_buf_count	512	io_uring registered buffer count

New Tests

• strikemq_test_circular_buffer — FixedCircularBuffer unit tests
• strikemq_test_sharded_log_map — ShardedLogMap unit tests
• All 5/5 tests pass on macOS

Verified On

• macOS (Apple Silicon, kqueue) — build + 5/5 tests + kcat smoke test + HTTP API
• Smoke test with kcat (produce, consume, keyed messages)

Full Changelog

See CHANGELOG.md for detailed changes, design decisions, and file-level diffs.

v0.1.4 — REST/HTTP Admin API

What's New

BlazeMQ now includes a built-in REST API on port 8080 — inspect and control the broker with just curl, no Kafka tooling required.

REST API Endpoints

Method	Path	Description
GET	/v1/broker	Broker info (version, uptime, config)
GET	/v1/topics	List all topics with partition count and offsets
GET	/v1/topics/{name}	Topic detail with per-partition offsets
DELETE	/v1/topics/{name}	Delete a topic and its data
GET	/v1/topics/{name}/messages?offset=0&limit=10	Peek at messages as JSON
POST	/v1/topics/{name}/messages	Produce messages via JSON body
GET	/v1/groups	List consumer groups
GET	/v1/groups/{id}	Group detail with members and committed offsets

Quick Example

# Start the broker
./blazemq

# Produce via REST
curl -X POST localhost:8080/v1/topics/demo/messages \
  -d '{"messages":[{"value":"hello"},{"key":"k1","value":"world"}]}'

# Peek at messages
curl "localhost:8080/v1/topics/demo/messages?offset=0&limit=10"

# Consume via Kafka — REST-produced messages are fully wire-compatible
kcat -b 127.0.0.1:9092 -C -t demo -e

Highlights

• Single-threaded HTTP/1.1 server with kqueue/epoll event loop (own thread)
• Minimal JSON writer — no library dependencies
• Messages produced via REST use Kafka v2 record batch format, consumable by any Kafka client
• Messages produced via Kafka clients are visible through the REST peek endpoint
• CORS headers included for browser-based tools
• Proper error responses with HTTP status codes (400, 404, 405, 413)

Bug Fixes

• Linux build fix — Removed duplicate size_t/uint64_t overload in JsonWriter that caused a compilation error on GCC (Linux). On GCC, size_t and uint64_t are the same type (unsigned long), while on Clang (macOS) they are distinct.

Verified On

• macOS (Apple Silicon, kqueue) — all tests pass, full REST + Kafka interop
• Linux (Ubuntu 22.04, GCC 11.4, epoll) — all tests pass, full REST + Kafka interop

Full Changelog

See CHANGELOG.md for detailed changes, design decisions, and verification steps.

v0.1.0

Initial release