INTEGRATION.md §3 used to show a sensor-poll thread calling
model->svids.set_value() directly while the io_context thread reads
the same SVID for an inbound S1F3. That's a data race — there are
zero locks anywhere in EquipmentDataModel and there's no intention
to add them. The library is single-threaded by design; the doc was
just inviting trouble.
This commit makes the actual contract explicit:
- INTEGRATION.md §3: thread-safety callout box. All access must run
on the io_context that drives the HSMS connection. Sensor updates
from other threads marshal via asio::post(io.get_executor(), ...).
Same applies to set_*_change_handler callbacks (they fire on the
io_context thread; observers must be thread-safe or hand work off).
- README.md §3 (Monitoring & observability): added a paragraph noting
that hooks fire on the io_context thread, blocking I/O inside a
handler stalls the dispatcher, and metrics exporters must respect
the same contract.
- tests/test_thread_safety.cpp: two scenarios that exercise the
canonical pattern — N producer threads asio::post sensor updates
onto a worker-driven io_context; reads marshal back through the
io. Catches obvious regressions (e.g. someone adding a
"convenience" cross-thread mutator that bypasses the strand).
A passing run isn't proof of race-freedom under ThreadSanitizer —
it pins down the *pattern* customers should follow. TSan integration
is a separate workstream.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
