Improve producer power formula

Signed-off-by: Matthias Wende <[email protected]>

Author: matthias-wende-frequenz

src/frequenz/sdk/timeseries/_formula_engine/_formula_generators/_producer_power_formula.py

@@ -5,12 +5,16 @@
 
 from __future__ import annotations
 
+import logging
+
 from ....microgrid import connection_manager
 from ....microgrid.component import ComponentCategory, ComponentMetricId
 from ..._quantities import Power
 from .._formula_engine import FormulaEngine
 from ._formula_generator import NON_EXISTING_COMPONENT_ID, FormulaGenerator
 
+_logger = logging.getLogger(__name__)
+
 
 class ProducerPowerFormula(FormulaGenerator[Power]):
     """Formula generator from component graph for calculating the Producer Power.
@@ -34,36 +38,37 @@ def generate(self) -> FormulaEngine[Power]:
         builder = self._get_builder(
             "producer_power", ComponentMetricId.ACTIVE_POWER, Power.from_watts
         )
+
         component_graph = connection_manager.get().component_graph
-        grid_successors = self._get_grid_component_successors()
-
-        if len(grid_successors) == 1:
-            grid_meter = next(iter(grid_successors))
-            if grid_meter.category != ComponentCategory.METER:
-                raise RuntimeError(
-                    "Only grid successor in the component graph is not a meter."
-                )
-            grid_successors = component_graph.successors(grid_meter.component_id)
-
-        first_iteration = True
-        for successor in iter(grid_successors):
-            # if in the future we support additional producers, we need to add them here
-            if component_graph.is_chp_chain(successor) or component_graph.is_pv_chain(
-                successor
-            ):
-                if not first_iteration:
-                    builder.push_oper("+")
-
-                first_iteration = False
-
-                builder.push_component_metric(
-                    successor.component_id,
-                    nones_are_zeros=successor.category != ComponentCategory.METER,
-                )
-
-        if first_iteration:
+        # if in the future we support additional producers, we need to add them to the lambda
+        producer_components = component_graph.dfs(
+            self._get_grid_component(),
+            set(),
+            lambda component: component_graph.is_pv_chain(component)
+            or component_graph.is_chp_chain(component),
+        )
+
+        if not producer_components:
+            _logger.warning(
+                "Unable to find any producer components in the component graph. "
+                "Subscribing to the resampling actor with a non-existing "
+                "component id, so that `0` values are sent from the formula."
+            )
+            # If there are no producer components, we have to send 0 values at the same
+            # frequency as the other streams.  So we subscribe with a non-existing
+            # component id, just to get a `None` message at the resampling interval.
             builder.push_component_metric(
                 NON_EXISTING_COMPONENT_ID, nones_are_zeros=True
             )
+            return builder.build()
+
+        for idx, component in enumerate(producer_components):
+            if idx > 0:
+                builder.push_oper("+")
+
+            builder.push_component_metric(
+                component.component_id,
+                nones_are_zeros=component.category != ComponentCategory.METER,
+            )
 
         return builder.build()