Addresses PR 191 reviewer feedback:
1. Shutdown drain
stop() now waits up to 5 s for in-flight _route_packet tasks to finish,
then cancels any that remain. Previously only the queue-consumer loop was
cancelled; created tasks were abandoned with no guarantee they completed.
Mechanism: _route_tasks set tracks live tasks (added on create, discarded
in the done-callback). stop() takes a snapshot and calls asyncio.wait()
with timeout=5.0, then cancels the still-pending subset.
2. Drop counter
_cap_drop_count increments each time a packet is dropped at the cap.
The running total is included in every WARNING log line and also printed
at shutdown so operators can tell at a glance whether the safety valve is
actually firing in production.
3. Tests (tests/test_packet_router.py)
test_cap_drops_packets_when_full — cap=3, send 8 → 5 drops, 3 in-flight
test_cap_drop_count_increments — count increments by 1 per drop
test_cap_drop_count_zero_... — count stays 0 when cap never reached
test_stop_waits_for_in_flight_tasks — slow task (0.2 s) completes, not cancelled
test_stop_cancels_tasks_...timeout — hanging task cancelled after timeout
test_route_tasks_set_cleaned_up — set empty after all tasks finish
test_counter_matches_set_size — _in_flight == len(_route_tasks) at cap
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Reviewer concern (PR 190):
The 1-second backoff sleep for local_transmission retry happened inside
`async with self._tx_lock`, blocking all other queued TX tasks for the
full second — hurting latency and throughput under load.
Fix — tighten lock scope to one attempt per acquisition:
Before: acquire lock → [attempt 0 → sleep(1) → attempt 1] → release
After: for each attempt:
[sleep(1) if retry] ← OUTSIDE the lock
acquire lock
re-check can_transmit ← fresh check every acquisition
attempt single send
record_tx on success
release lock
The duty-cycle gate now runs on every lock acquisition (not just the first),
which is correct: airtime state may change during the backoff sleep.
Tests added (tests/test_tx_lock.py):
1. test_concurrent_sends_do_not_interleave — two tasks racing to the same
delay timer must never overlap inside send_packet.
2. test_duty_cycle_toctou_is_fixed — second packet is dropped when the
first consumes the budget inside the lock.
3. test_local_retry_releases_lock_during_backoff — a concurrent relayed
packet fires at ~0.1s while local retry sleeps 1s; confirms it is not
blocked by the backoff.
4. test_non_local_failure_propagates — relayed send failure raises
immediately with exactly one attempt.
5. test_duty_cycle_rechecked_on_retry — if the budget is exhausted during
backoff, the retry is dropped by the in-lock gate (not sent).
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Lloyd