use singular preferred detector in workflow processing

Author: Cathy Teng

src/sentry/workflow_engine/processors/detector.py

@@ -301,6 +301,10 @@ def get_detectors_for_event(
 
 
 def get_detector_by_event(event_data: WorkflowEventData) -> Detector:
+    """
+    Returns the detector from the GroupEvent in event_data.
+    """
+
     evt = event_data.event
 
     if not isinstance(evt, GroupEvent):
@@ -311,7 +315,7 @@ def get_detector_by_event(event_data: WorkflowEventData) -> Detector:
     issue_occurrence = evt.occurrence
 
     try:
-        if issue_occurrence is None or evt.group.issue_type.detector_settings is None:
+        if issue_occurrence is None or evt.group.issue_type == ErrorGroupType:
             # if there are no detector settings, default to the error detector
             detector = Detector.get_error_detector_for_project(evt.project_id)
         else:
@@ -361,9 +365,16 @@ def get_detector_by_group(group: Group) -> Detector:
 
 
 def get_detector_from_event_data(event_data: WorkflowEventData) -> Detector:
+    """
+    Essentially the same as get_detectors_for_event except we look up the detector for the Activity instead of expecting it to be passed in.
+    """
+
     try:
         if isinstance(event_data.event, GroupEvent):
-            return get_detector_by_event(event_data)
+            event_detectors = get_detectors_for_event(event_data)
+            if event_detectors is None:
+                raise Detector.DoesNotExist("No detectors found for event")
+            return event_detectors.preferred_detector
         elif isinstance(event_data.event, Activity):
             return get_detector_by_group(event_data.group)
         else:

src/sentry/workflow_engine/processors/workflow.py

@@ -1,4 +1,4 @@
-from collections.abc import Collection, Sequence
+from collections.abc import Sequence
 from dataclasses import asdict, replace
 from datetime import datetime
 from enum import StrEnum
@@ -380,7 +380,7 @@ def get_environment_by_event(event_data: WorkflowEventData) -> Environment | Non
 
 @scopedstats.timer()
 def _get_associated_workflows(
-    detectors: Collection[Detector], environment: Environment | None, event_data: WorkflowEventData
+    detector: Detector, environment: Environment | None, event_data: WorkflowEventData
 ) -> set[Workflow]:
     """
     This is a wrapper method to get the workflows associated with a detector and environment.
@@ -394,7 +394,7 @@ def _get_associated_workflows(
     workflows = set(
         Workflow.objects.filter(
             environment_filter,
-            detectorworkflow__detector_id__in=[detector.id for detector in detectors],
+            detectorworkflow__detector_id=detector.id,
             enabled=True,
         )
         .select_related("environment")
@@ -421,7 +421,7 @@ def _get_associated_workflows(
                 "event_data": asdict(event_data),
                 "event_environment_id": environment.id if environment else None,
                 "workflows": [workflow.id for workflow in workflows],
-                "detector_types": [detector.type for detector in detectors],
+                "detector_type": detector.type,
             },
         )
 
@@ -500,7 +500,9 @@ def process_workflows(
     if features.has("organizations:workflow-engine-process-workflows-logs", organization):
         log_context.set_verbose(True)
 
-    workflows = _get_associated_workflows(event_detectors.detectors, environment, event_data)
+    workflows = _get_associated_workflows(
+        event_detectors.preferred_detector, environment, event_data
+    )
     workflow_evaluation_data.workflows = workflows
 
     if not workflows:

tests/sentry/workflow_engine/processors/test_workflow.py

@@ -464,8 +464,8 @@ def test_uses_issue_stream_workflows(self) -> None:
         assert len(result.data.triggered_actions) == 0
 
     @override_options({"workflow_engine.exclude_issue_stream_detector": False})
-    def test_multiple_detectors(self) -> None:
-        issue_stream_workflow, issue_stream_detector, _, _ = self.create_detector_and_workflow(
+    def test_multiple_detectors__preferred(self) -> None:
+        _, issue_stream_detector, _, _ = self.create_detector_and_workflow(
             name_prefix="issue_stream",
             workflow_triggers=self.create_data_condition_group(),
             detector_type=IssueStreamGroupType.slug,
@@ -476,7 +476,7 @@ def test_multiple_detectors(self) -> None:
         )
 
         result = process_workflows(self.batch_client, self.event_data, FROZEN_TIME)
-        assert result.data.triggered_workflows == {self.error_workflow, issue_stream_workflow}
+        assert result.data.triggered_workflows == {self.error_workflow}
         assert result.data.associated_detector == self.error_detector