feat(workflow_engine): Add in hook for producing occurrences from the stateful detector

[everettbu]

Test [new PR number opened]

[greptile-apps]

Greptile Summary

This PR implements a significant architectural enhancement to Sentry's workflow engine by adding the ability for stateful detectors to produce issue occurrences. The changes span across four main files:

Core Model Enhancement (detector.py): A new group_type property is added to the Detector model, providing typed access to the GroupType instance associated with each detector. This refactors the existing detector_handler property to eliminate code duplication and improve type safety by centralizing the group type lookup logic.

Handler Migration (grouptype.py): The MetricAlertDetectorHandler is refactored to inherit from StatefulDetectorHandler instead of DetectorHandler, removing its concrete evaluate() method implementation. This aligns with the broader migration towards stateful detection capabilities.

Processor Core Logic (detector.py): The most substantial changes occur in the processor, where the detector evaluation pipeline is enhanced to support occurrence production. Key modifications include:

• Changing return types from lists to dictionaries keyed by DetectorGroupKey to eliminate duplicate handling
• Adding a new abstract method build_occurrence_and_event_data that subclasses must implement
• Integrating Kafka occurrence production when detectors transition to non-OK status
• Removing redundant duplicate detection logic in favor of dictionary-based deduplication

Test Infrastructure (test_detector.py): Comprehensive test updates validate the new occurrence production functionality, including mock implementations of the abstract method and verification of Kafka integration.

These changes enable the workflow engine to create and emit proper IssueOccurrence objects to Kafka when detectors identify problems, completing the integration between the detection system and Sentry's issue tracking infrastructure. The architecture now supports both issue creation (via occurrences) and resolution (via status change messages).

Confidence score: 2/5

• This PR introduces significant architectural changes but has several implementation gaps that make it risky to merge
• The score reflects incomplete abstract method implementations and potential runtime failures in the MetricAlertDetectorHandler
• Files needing attention: src/sentry/incidents/grouptype.py (incomplete implementation), src/sentry/workflow_engine/processors/detector.py (verify abstract method contracts)

_{4 files reviewed, 3 comments}

_{Edit Code Review Bot Settings | Greptile}

[greptile-apps]

logic: StatefulDetectorHandler is an abstract base class that requires implementing several abstract methods: counter_names, get_dedupe_value, get_group_key_values, and build_occurrence_and_event_data. This class will not be instantiable without these implementations.

[greptile-apps]

logic: The hardcoded value 6 for group_2 seems inconsistent - the test data shows group_2 has value 10, but the expected occurrence is built with value 6

Suggested change

	occurrence_2, event_data_2 = build_mock_occurrence_and_event(
	detector.detector_handler, "group_2", 6, PriorityLevel.HIGH
	occurrence_2, event_data_2 = build_mock_occurrence_and_event(
	detector.detector_handler, "group_2", 10, PriorityLevel.HIGH

[greptile-apps]

logic: The test builds an expected result using build_mock_occurrence_and_event with 'val1' and value 6, but this doesn't match the test's group_key parameter 'group_key' - potential test logic error

[GitHoobar]

Review Summary

🏷️ Draft Comments (1)

Skipped posting 1 draft comments that were valid but scored below your review threshold (>=13/15). Feel free to update them here.

src/sentry/workflow_engine/models/detector.py (1)

59-61: group_type property calls grouptype.registry.get_by_slug(self.type) on every access, causing repeated registry lookups for the same detector and wasting CPU if accessed frequently.

📊 Impact Scores:

• Production Impact: 2/5
• Fix Specificity: 4/5
• Urgency Impact: 2/5
• Total Score: 8/15

🤖 AI Agent Prompt (Copy & Paste Ready):

In src/sentry/workflow_engine/models/detector.py, lines 59-61, the `group_type` property performs a registry lookup on every access, which is inefficient if accessed frequently. Decorate the property with `@functools.lru_cache(maxsize=1)` to cache the result per instance and avoid repeated lookups. Ensure you import `functools` at the top of the file if not already present.

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