Event Transformation
Event transformation patterns enable converting one event type to another, enriching event data, and creating custom event flows for specialized processing.
Pattern Overview
This pattern enables:
- Type Conversion: Transform built-in events to custom events
- Data Enrichment: Add context and metadata to events
- Event Splitting: Convert one event into multiple specialized events
- Event Aggregation: Combine multiple events into summary events
Key Components
Events
- Source Events: Original events to be transformed
- Target Events: New events created from transformations
- Custom Events: Domain-specific event types for your application
Routes
- Transform Mapping: Use
map()
to convert event types - Broadcasting: Send transformed events through the system
- Filtering: Apply transformations conditionally
Transformation Functions
- Pure Transformations: Convert data without side effects
- Enrichment: Add external data to events
- Analysis: Extract insights and create derived events
Basic Transformation Example
Advanced Transformation Patterns
Multi-Target Transformation
Event Aggregation
Conditional Transformation
Real-time Enrichment
Event Chain Transformation
Best Practices
- Type Safety: Use Pydantic models for all custom events
- Documentation: Document what each transformation does and why
- Error Handling: Handle transformation failures gracefully
- Performance: Cache expensive operations like API calls
- Selective Processing: Use filters to avoid unnecessary transformations
- Event Naming: Use clear, domain-specific event names
- Versioning: Consider event schema versioning for evolving systems
Common Use Cases
- Analytics Pipeline: Transform user interactions into analytics events
- Domain Events: Convert generic events to business domain events
- Monitoring: Transform application events into monitoring/alerting events
- Integration: Convert events for external system integration
- State Machine: Transform events based on current system state
- A/B Testing: Create different event streams for testing variants
Troubleshooting
Missing Transformations
- Verify event type matching in
.on()
clauses - Check that transformation functions return correct types
- Ensure broadcasted events are subscribed to by other bridges
Performance Issues
- Use async transformations for I/O operations
- Cache frequently accessed external data
- Consider batch processing for high-volume transformations
Data Quality
- Validate transformed data with Pydantic models
- Add logging to track transformation success/failure rates
- Monitor for missing or corrupted event data
This pattern is essential for building event-driven systems that adapt events to different processing contexts.