Book Release Note v0.2.0 — 2026-08-17

v0.2.0 — 2026-08-17

nqbook stopped being a smoke test and became a service: it now takes a live feed and persists everything it books.

• Three threads, two queues. Pipeline.h declares the stage contracts — feed, book, writer — and joins each pair with one nlib::single_queue (SPSC), so the process runs lock-free end to end. A full queue makes the producer wait rather than drop, so backpressure from storage reaches ZMQ.
• The feed is a ZMQ SUB socket. Framing is one tag byte followed by the record in host layout; anything that matches no tag-plus-size is dropped. order::prev / order::next arrive as wire bytes and are discarded — the hooks are book-owned state.
• Parquet persistence. The writer keeps one sink per record type, buffers 1024 rows into Arrow builders, and writes each batch as one zstd-compressed row group. Files land in data_out/, stamped with the writer start time, with the Arrow schema embedded so readers restore the fixed-size lists in book. A storage error aborts the process; running on without persistence would lose data silently.
• Snapshots are on the wall clock, every 3 s, whether or not the book saw an event.
• Shutdown drains. SIGINT or SIGTERM stops the stages upstream-first — feed, then book, then writer — and each drains its input before returning, so every received record reaches a file.
• Configuration is nqbook [feed_endpoint] [out_dir], with the endpoint falling back to NQBOOK_FEED_ENDPOINT and then to tcp://host.docker.internal:5555.
• The build needs Arrow, Parquet, and cppzmq, which only the dev container carries — the host can no longer configure this project.
• nlib bumped to 84ee2cc: order::side and trade::side are now declared nlib::side, without which this repository does not compile under GCC 13.