Small debugging enhancements (#1119)

- **Fix wrong term in battery formula documentation**
- **Give more receivers/tasks a name for easier debugging**
- **Add a nice str representation for `Sample`**
- **Actually log the error that caused a source to be removed**
- **Add more details to "no relevant sample found" warning log**
- **Add change log**

RELEASE_NOTES.md

@@ -10,7 +10,9 @@
 
 ## New Features
 
-<!-- Here goes the main new features and examples or instructions on how to use them -->
+* Many tasks, senders and receivers now have proper names for easier debugging.
+* The resample log was improved to show more details.
+* The `Sample` class now has a nice `__str__` representation.
 
 ## Bug Fixes
 

src/frequenz/sdk/microgrid/_data_pipeline.py

@@ -479,7 +479,8 @@ def _resampling_request_sender(self) -> Sender[ComponentMetricRequest]:
                 channel_registry=self._channel_registry,
                 data_sourcing_request_sender=self._data_sourcing_request_sender(),
                 resampling_request_receiver=channel.new_receiver(
-                    limit=_REQUEST_RECV_BUFFER_SIZE
+                    limit=_REQUEST_RECV_BUFFER_SIZE,
+                    name=channel.name + " Receiver",
                 ),
                 config=self._resampler_config,
             )

src/frequenz/sdk/microgrid/_data_sourcing/microgrid_api_source.py

@@ -461,7 +461,8 @@ async def _update_streams(
             self.comp_data_tasks[comp_id].cancel()
 
         self.comp_data_tasks[comp_id] = asyncio.create_task(
-            run_forever(lambda: self._handle_data_stream(comp_id, category))
+            run_forever(lambda: self._handle_data_stream(comp_id, category)),
+            name=f"{type(self).__name__}._update_stream({comp_id=}, {category.name})",
         )
 
     async def add_metric(self, request: ComponentMetricRequest) -> None:

src/frequenz/sdk/microgrid/_resampling.py

@@ -179,7 +179,11 @@ def _log_resampling_task_error(self, resampling_task: asyncio.Task[None]) -> Non
             resampling_task.result()
         except ResamplingError as error:
             for source, source_error in error.exceptions.items():
-                _logger.error("Error resampling source %s, removing source...", source)
+                _logger.error(
+                    "Error resampling source %s, removing source",
+                    source,
+                    exc_info=source_error,
+                )
                 removed = self._resampler.remove_timeseries(source)
                 if not removed:
                     _logger.error(

src/frequenz/sdk/timeseries/_base_types.py

@@ -34,6 +34,14 @@ class Sample(Generic[QuantityT]):
     value: QuantityT | None = None
     """The value of this sample."""
 
+    def __str__(self) -> str:
+        """Return a string representation of the sample."""
+        return f"{type(self).__name__}({self.timestamp}, {self.value})"
+
+    def __repr__(self) -> str:
+        """Return a string representation of the sample."""
+        return f"{type(self).__name__}({self.timestamp=}, {self.value=})"
+
 
 @dataclass(frozen=True)
 class Sample3Phase(Generic[QuantityT]):

src/frequenz/sdk/timeseries/_resampling.py

@@ -744,14 +744,43 @@ def resample(self, timestamp: datetime) -> Sample[Quantity]:
         # resort to some C (or similar) implementation.
         relevant_samples = list(itertools.islice(self._buffer, min_index, max_index))
         if not relevant_samples:
-            _logger.warning("No relevant samples found for: %s", self._name)
+            self._log_no_relevant_samples(minimum_relevant_timestamp, timestamp)
+
         value = (
             conf.resampling_function(relevant_samples, conf, props)
             if relevant_samples
             else None
         )
         return Sample(timestamp, None if value is None else Quantity(value))
 
+    def _log_no_relevant_samples(
+        self, minimum_relevant_timestamp: datetime, timestamp: datetime
+    ) -> None:
+        """Log that no relevant samples were found.
+
+        Args:
+            minimum_relevant_timestamp: Minimum timestamp that was requested
+            timestamp: Timestamp that was requested
+        """
+        if not _logger.isEnabledFor(logging.WARNING):
+            return
+
+        if self._buffer:
+            buffer_info = (
+                f"{self._buffer[0].timestamp} - "
+                f"{self._buffer[-1].timestamp} ({len(self._buffer)} samples)"
+            )
+        else:
+            buffer_info = "Empty"
+
+        _logger.warning(
+            "No relevant samples found for: %s\n  Requested: %s - %s\n     Buffer: %s",
+            self._name,
+            minimum_relevant_timestamp,
+            timestamp,
+            buffer_info,
+        )
+
 
 class _StreamingHelper:
     """Resample data coming from a source, sending the results to a sink."""

src/frequenz/sdk/timeseries/formula_engine/_formula_generators/_battery_power_formula.py

@@ -24,7 +24,7 @@
 
 
 class BatteryPowerFormula(FormulaGenerator[Power]):
-    """Creates a formula engine from the component graph for calculating grid power."""
+    """Creates a formula engine from the component graph for calculating battery power."""
 
     def generate(
         self,