Ensure component data is stale after receiving a timer event

Because of the nature of async, it might happen that data is slightly
delayed, so a timer event gets triggered, but component data arrives
before the timer event arrives,  and in such cases, we end up going
into a bad state.

This issue is resolved in this PR, by checking that the component data
is actually late, every time a timer triggers.

Signed-off-by: Sahas Subramanian <[email protected]>

Author: shsms

src/frequenz/sdk/actor/power_distributing/_battery_status.py

@@ -339,9 +339,25 @@ async def _run(
                         self._handle_status_set_power_result(selected.value)
 
                     elif selected_from(selected, battery_timer):
+                        if (
+                            datetime.now(tz=timezone.utc)
+                            - self._battery.last_msg_timestamp
+                        ) < timedelta(seconds=self._max_data_age):
+                            # This means that we have received data from the battery
+                            # since the timer triggered, but the timer event arrived
+                            # late, so we can ignore it.
+                            continue
                         self._handle_status_battery_timer()
 
                     elif selected_from(selected, inverter_timer):
+                        if (
+                            datetime.now(tz=timezone.utc)
+                            - self._inverter.last_msg_timestamp
+                        ) < timedelta(seconds=self._max_data_age):
+                            # This means that we have received data from the inverter
+                            # since the timer triggered, but the timer event arrived
+                            # late, so we can ignore it.
+                            continue
                         self._handle_status_inverter_timer()
 
                     else: