fix: clarify _send_packet()/_send_ack() scheduling contract (#263)

Replace misleading bare 'pass' with explicit comment explaining that
PacketTrack polling is handled by PacketSendSchedulerThread /
AckSendSchedulerThread.  Restructure condition to
'if not (scheduler and scheduler.is_alive()):' so the fallback
thread is only started when the scheduler is genuinely unavailable.

Closes #244

ChangeLog.md

@@ -18,6 +18,8 @@ Generated by [`auto-changelog`](https://github.com/CookPete/auto-changelog).
 
 - Fix deprecated datetime.utcfromtimestamp()/utcnow() calls — replace with timezone-aware equivalents [`e7b0a19`](https://github.com/craigerl/aprsd/commit/e7b0a19)
 
+- Fix _send_packet()/_send_ack(): replace misleading `pass` with explicit comment explaining PacketTrack polling contract; restructure condition to `if not (scheduler and scheduler.is_alive()):` [`2842851`](https://github.com/craigerl/aprsd/commit/2842851)
+
 - Add reset() to @singleton decorator; update tests to use ClassName.reset() instead of ClassName.instance = None [`ef19aaa`](https://github.com/craigerl/aprsd/commit/ef19aaa)
 
 - Fix PacketTrack.keys/items/values — return list snapshots instead of live dict views outside the lock [`088436e`](https://github.com/craigerl/aprsd/commit/088436e)

aprsd/threads/tx.py

@@ -68,13 +68,15 @@ def send(packet: core.Packet, direct=False, aprs_client=None):
 @msg_throttle_decorator.sleep_and_retry
 def _send_packet(packet: core.Packet, direct=False, aprs_client=None):
     if not direct:
-        # Use threadpool scheduler instead of creating individual threads
+        # The packet was already registered in PacketTrack via
+        # collector.PacketCollector().tx(packet) in send() before this
+        # function was called.  PacketSendSchedulerThread polls PacketTrack
+        # every second and will find the packet there — nothing more needs
+        # to be done here.  The scheduler is started (or confirmed alive)
+        # as a side-effect of _get_packet_scheduler().
         scheduler = _get_packet_scheduler()
-        if scheduler and scheduler.is_alive():
-            # Scheduler will handle the packet
-            pass
-        else:
-            # Fallback to old method if scheduler not available
+        if not (scheduler and scheduler.is_alive()):
+            # Fallback: scheduler failed to start — send directly in a thread
             thread = SendPacketThread(packet=packet)
             thread.start()
     else:
@@ -84,13 +86,12 @@ def _send_packet(packet: core.Packet, direct=False, aprs_client=None):
 @ack_throttle_decorator.sleep_and_retry
 def _send_ack(packet: core.AckPacket, direct=False, aprs_client=None):
     if not direct:
-        # Use threadpool scheduler instead of creating individual threads
+        # Same implicit handoff as _send_packet: the ack was registered in
+        # PacketTrack before this call; AckSendSchedulerThread polls and
+        # picks it up.  Starting/verifying the scheduler is all that's needed.
         scheduler = _get_ack_scheduler()
-        if scheduler and scheduler.is_alive():
-            # Scheduler will handle the packet
-            pass
-        else:
-            # Fallback to old method if scheduler not available
+        if not (scheduler and scheduler.is_alive()):
+            # Fallback: scheduler failed to start — send directly in a thread
             thread = SendAckThread(packet=packet)
             thread.start()
     else: