Introduction
When processing documents in Kodexa, effective state management is crucial for building reliable and maintainable systems. This article explores how to implement a state machine approach for document processing, addressing common challenges and providing concrete implementation examples.Beyond Event-Driven Processing
Many document processing implementations start with simple event reactions. While intuitive, this approach can become problematic as your system grows:- Event-driven systems often become “chatty” with excessive message volume
- Processing may occur without awareness of the document’s current state
- Document family events occur frequently, making it difficult to track meaningful state changes
- Failure handling becomes complex and inconsistent
The State Machine Approach
A more robust solution is to design a clear state machine for your document processing workflow. For example:- Defining document statuses in the Manage Project section
- Adding status update models at the end of each processing pipeline
- Triggering subsequent processing based on status changes rather than generic events
Best Practices for Pipeline Design
When building pipelines in Kodexa:- End-of-Pipeline Status Updates: Each pipeline should conclude by setting an appropriate document status:
- Status-Driven Workflows: Subsequent processing steps should trigger based on document status changes rather than generic events
- External System Synchronization: Use the Apply Status model to synchronize with external systems:
Handling Failures with the Document Retry Model
Failure handling requires special consideration. Rather than immediately marking documents as failed, Kodexa’s Document Retry model provides a robust approach:- Scheduled Execution: The model runs on a schedule rather than being event-triggered, allowing for controlled retry attempts
- Label-Based Tracking: It uses document labels with incrementing counters (e.g., “retry-1”, “retry-2”) to track attempts
- Configurable Retry Limit: It applies a cap on retry attempts before marking as permanently failed
- Efficient Filtering: It uses query filters to only process documents that need attention
Implementing a Failure Notification Model
For reporting failures to external systems, implement a scheduled model that checks for failed documents:- Pause retries during system issues without losing track of failures
- Create dedicated monitoring for failure conditions
- Control the cadence of failure reporting independently from processing
Implementation Considerations
When implementing this state-based approach:- Separation of Concerns: Keep retry logic separate from normal processing pipelines
- Stateful Tracking: Use document labels or status to track progress through the workflow
- Progressive Processing: Ensure documents flow through the state machine with clear transitions
- Controlled Scheduling: Use scheduled events rather than reactive ones for error handling and retries