Replace the _route_tasks set in PacketRouter with a simple integer counter
(_in_flight / _max_in_flight=30) and add an early-drop guard in _process_queue.
Problems solved:
1. No cap on concurrent sleeping tasks: burst arrivals (multi-hop amplification,
collision retries) could stack unbounded _route_packet tasks, each holding a
packet closure and asyncio Task overhead, before the duty-cycle gate fired.
2. _route_tasks set held a strong reference to every Task object for the full
duration of its sleep — unnecessary in Python 3.12+ where the event loop
already holds tasks alive.
3. stop() iterated the full set to cancel tasks on shutdown — O(n) where n is
the in-flight count at shutdown time.
Fix: _in_flight counter increments before create_task and decrements in the
_on_route_done callback. The cap check (>= 30) in _process_queue is a last-resort
safety valve — LoRa airtime and the duty-cycle gate keep _in_flight in the
low single digits under normal load.
Also lower companion dedup prune threshold from 1000 to 200: the original 1000
allowed stale entries to accumulate for hundreds of PATH packets before the
O(n) dict comprehension sweep ran.
Trade-off documented: explicit task cancellation on shutdown is removed; tasks
are cancelled implicitly by event loop shutdown with identical outcome (no packet
transmits after the radio is closed regardless).
Docs: docs/pr_in_flight_cap.md — full problem analysis, alternative approaches
(semaphore, keep set + add cap), proof of counter sufficiency, rationale for
cap=30, and unit + field test plan.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
This commit sets up the initial project structure for the PyMC Repeater Daemon.
It includes base configuration files, dependency definitions, and scaffolding
for the main daemon service responsible for handling PyMC repeating operations.
