Fulfillment Service

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Overview

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Responsibilities

• Generate tickets after successful payment
• Create PDF tickets with QR codes for venue entry
• Store ticket PDFs in local file storage
• Track ticket status (pending, generated, failed, delivered)
• Publish ticket-issued events to Kafka
• Serve ticket PDFs via HTTP endpoints
• Enrich ticket data by querying Ordering service

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API Endpoints

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Get Ticket PDF

[HttpGet("{id}")]
public async Task<IActionResult> GetTicketPdf(string id)
{
    // Strip .pdf extension if present
    if (id.EndsWith(".pdf", StringComparison.OrdinalIgnoreCase))
    {
        id = id.Substring(0, id.Length - 4);
    }

    if (!Guid.TryParse(id, out var ticketId))
    {
        return BadRequest("Invalid ticket ID format. Expected a GUID.");
    }

    var ticket = await _ticketRepository.GetByIdAsync(ticketId);
    if (ticket == null)
        return NotFound("Ticket not found in database");

    var fileName = $"{ticketId}.pdf";
    var filePath = Path.Combine(_storagePath, fileName);

    if (!System.IO.File.Exists(filePath))
    {
        return NotFound("PDF file not found on disk");
    }

    var bytes = await System.IO.File.ReadAllBytesAsync(filePath);
    return File(bytes, "application/pdf", fileName);
}

• 400 Bad Request: Invalid GUID format
• 404 Not Found: Ticket not found in database or PDF file missing

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Domain Models

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Ticket

public class Ticket
{
    public Guid Id { get; set; }
    public Guid OrderId { get; set; }
    public string CustomerEmail { get; set; } = string.Empty;
    public string EventName { get; set; } = string.Empty;
    public string SeatNumber { get; set; } = string.Empty;
    public decimal Price { get; set; }
    public string Currency { get; set; } = "USD";
    public TicketStatus Status { get; set; }
    public string QrCodeData { get; set; } = string.Empty;
    public string TicketPdfPath { get; set; } = string.Empty;
    public DateTime GeneratedAt { get; set; }
    public DateTime CreatedAt { get; set; }
    public DateTime UpdatedAt { get; set; }
}

public enum TicketStatus
{
    Pending = 0,
    Generated = 1,
    Failed = 2,
    Delivered = 3
}

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Configuration

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Database Connection

{
  "ConnectionStrings": {
    "Default": "Host=postgres;Port=5432;Database=ticketing;Username=postgres;Password=postgres"
  }
}

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Kafka Configuration

{
  "Kafka": {
    "BootstrapServers": "kafka:9092",
    "ConsumerGroupId": "fulfillment-service",
    "Topics": {
      "PaymentSucceeded": "payment-succeeded",
      "TicketIssued": "ticket-issued"
    }
  }
}

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File Storage

/app/data/tickets/{ticketId}.pdf

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Ticket Generation Flow

1. Listen for payment-succeeded event: Kafka consumer receives event from Payment service
2. Extract order details: Parse OrderId from the event payload
3. Enrich ticket data: Query Ordering service for order details (customer, event, seat)
4. Generate QR code: Create QR code data for ticket validation
5. Create ticket record: Insert ticket into database with Pending status
6. Generate PDF: Create PDF ticket with event details, seat info, and QR code
7. Save PDF: Store PDF in local file storage (/app/data/tickets/)
8. Update ticket status: Mark ticket as Generated
9. Publish event: Send ticket-issued event to Kafka with ticket details
10. Notification triggered: Notification service consumes event and sends email

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Kafka Integration

• payment-succeeded: Triggers ticket generation flow
  • Payload: { OrderId, CustomerId, Amount, ... }

• ticket-issued: Published after successful ticket generation
  • Payload: { TicketId, OrderId, CustomerEmail, TicketPdfUrl, QrCodeData, ... }
  • Consumed by Notification service to send tickets via email

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PDF Generation

• Event name and details
• Customer information
• Seat information (section, row, number)
• Purchase price
• QR code for venue scanning
• Ticket ID and order reference
• Generation timestamp

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File Storage

• Development: /app/data/tickets/
• Docker: Mounted volume fulfillment-data:/app/data/tickets
• Filename format: {ticketId}.pdf

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Architecture Notes

• Uses MediatR for CQRS-style command/query handling
• Infrastructure services registered via AddInfrastructure() extension method
• Listens to Kafka for payment-succeeded events
• Queries Ordering service via HTTP for order enrichment
• Stores PDFs locally (could be extended to use S3, Azure Blob, etc.)
• Publishes ticket-issued events for downstream notification delivery

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Error Handling

• If ticket generation fails, status is set to Failed
• Failed tickets can be retried via background job
• Missing PDF files return 404 but ticket record may still exist
• Idempotency: Re-processing same OrderId won’t create duplicate tickets