order_processing

Order Processing Workflow Example

This example demonstrates a comprehensive order processing workflow using the Petri net-based workflow engine. It showcases realistic business logic including payment processing, inventory management, and order fulfillment.

Workflow Overview

The order processing workflow consists of the following states and transitions:

States (Places)

• pending: Initial state when order is created
• payment_processing: Payment is being processed
• payment_approved: Payment was successful
• payment_failed: Payment failed
• inventory_check: Checking if items are in stock
• inventory_insufficient: Not enough stock available
• shipping: Order is being shipped
• delivered: Order has been delivered
• cancelled: Order was cancelled
• refunded: Order was refunded

Key Transitions

• process_payment: pending → payment_processing
• payment_success: payment_processing → payment_approved
• payment_failure: payment_processing → payment_failed
• retry_payment: payment_failed → payment_processing
• check_inventory: payment_approved → inventory_check
• inventory_available: inventory_check → shipping
• inventory_insufficient: inventory_check → inventory_insufficient
• restock_and_ship: inventory_insufficient → shipping
• mark_delivered: shipping → delivered
• refund_order: delivered → refunded

Business Logic Components

Order Management

• Order: Represents an order with items, customer info, and status
• OrderItem: Individual items in an order with quantity and pricing

Payment Processing

• PaymentProcessor: Simulates payment processing with configurable success rate
• Handles payment retries and failure scenarios
• Simulates processing delays for realism

Inventory Management

• Inventory: Manages product stock levels
• Checks availability before shipping
• Handles restocking scenarios
• Prevents overselling

Features Demonstrated

1. Event-Driven Architecture: Uses workflow events to trigger business logic
2. Error Handling: Comprehensive error handling for each transition
3. Context Management: Stores order data and business state in workflow context
4. Realistic Simulation: Simulates real-world scenarios like payment failures and inventory shortages
5. State Persistence: Maintains order status throughout the workflow
6. Visualization: Generates Mermaid diagrams for workflow visualization

Running the Example

cd examples/order_processing
go run main.go

Example Output

The example will demonstrate:

1. Order Creation: Creates a sample order with multiple items
2. Payment Processing: Simulates payment with success/failure scenarios
3. Inventory Check: Verifies stock availability
4. Shipping Process: Handles the shipping workflow
5. Delivery Confirmation: Marks order as delivered
6. Status Reporting: Shows final order status and workflow diagram

Key Learning Points

• Workflow Design: How to design complex business workflows with multiple paths
• Event Handling: Using events to trigger business logic at specific workflow stages
• Error Recovery: Handling failure scenarios and retry logic
• State Management: Managing complex state across multiple workflow stages
• Business Integration: Integrating external systems (payment, inventory) with workflows

Extending the Example

You can extend this example by:

1. Adding Database Storage: Integrate with the WorkflowManager for persistent storage
2. Web Interface: Add HTTP endpoints for order management
3. Notification System: Add email/SMS notifications at key stages
4. Analytics: Track workflow performance and bottlenecks
5. Parallel Processing: Add concurrent inventory checks for multiple warehouses

Integration with Workflow Manager

This example can be enhanced with the WorkflowManager for production use:

// Create manager with SQLite storage
manager := workflow.NewManager(storage.NewSQLiteStorage("orders.db"))

// Save workflow instance
err := manager.SaveWorkflow(wf)

// Load workflow instance
wf, err := manager.LoadWorkflow("order-123")

This provides persistent storage, workflow instance management, and better scalability for production environments.