Queue-Based Ticket Booking System

A scalable, real-time ticket reservation system built with Go, Redis, and PostgreSQL. Users join a queue for tickets, and background processors manage reservations, stock, and cleanup.

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Features

• Queue-Based Booking
  • Users join a Redis-backed queue (queue:<ticket_type_id>) to request tickets.
  • Background processor dequeues users and attempts to reserve tickets.
• Reservation System
  • Dequeued users are given a temporary reservation stored as a Redis hash (reservation:<token>).
  • Reservations auto-expire after 2 minutes.
• Stock Management
  • Stock is managed in PostgreSQL via the ticket_types table.
  • On successful reservation, DB stock is decreased by 1.
  • Reservation status and mapping are tracked via Redis with TTL.
• Auto Expiry & Stock Refill
  • Cleanup goroutine checks for expired reservations every 30 seconds.
  • If a reservation expires (TTL = 0), DB stock is refilled by +1.
  • Expired Redis keys (reservation:* and mapping keys) are deleted.
• HTTP API Endpoints
  • POST /queue/join: Join a Redis queue for a ticket.
  • GET /reservation/status: Check if a reservation is confirmed.
  • POST /reservation/confirm: Confirm reservation and finalize ticket.
  • GET /events: List all events (with ticket types).
• Reservation Lifecycle
  • User joins queue → stored in Redis list queue:<ticket_type_id>
  • Processor dequeues token, checks DB stock.
  • If stock available:
    • Reserve ticket.
    • Decrease stock in DB.
    • Store Redis key reservation:<token> with TTL = 2 min.
    • Map token to ticket type (token-ticket-type:<token>).
  • If reservation not confirmed within 2 min:
    • Cleaner detects TTL expiry.
    • Restores DB stock.
    • Deletes Redis keys.
  • If reservation confirmed:
    • /reservation/confirm finalizes it (optional: mark status in DB).

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Technologies

• Go: HTTP server, Redis & SQL handling, background goroutines.
• Redis: Queue (LPUSH/LPOP), reservation hashes, TTL, cleanup.
• PostgreSQL: Ticket types table for real stock control.
• Gorilla Mux: HTTP routing.
• sqlx: Simplified DB access.
• go-redis: Redis client.

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How to Run

1. Start Redis and PostgreSQL
   • Ensure both services are running and properly configured.
2. Load DB Schema
   • Load your database schema (includes ticket_types, events, etc.).
3. Run the Server

go run main.go

• The queue processor and cleaner run automatically as background goroutines.

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API Reference

Method	Route	Description
POST	/queue/join	Join a Redis queue for a ticket
GET	/reservation/status	Check if a reservation is confirmed
POST	/reservation/confirm	Confirm reservation and finalize ticket
GET	/events	List all events (with ticket types)