Cafe Order Management Simulator

A concurrent and distributed cafe order management simulator developed as part of the Operating Systems course project under the supervision of Dr. Khanmirza at K. N. Toosi University of Technology.

The system simulates a real-world cafe environment using multi-threading, concurrency control mechanisms, and Inter-Process Communication (IPC).

Features & Architecture

1. Core Simulation (Main Process)

• Order Generation (Producers): 3 dedicated threads dynamically create random orders (up to 50 total orders) with unique IDs, customer names, drink types, preparation times, and priorities.
• Baristas (Consumers): 4 parallel barista threads process incoming orders from a shared queue, withdraw required ingredients, and coordinate device usages.
• Bounded Buffer Queue: A shared order queue with a strict capacity limit of 10. Thread synchronization is handled via Semaphores (to track available empty spaces and items) and a ReentrantLock (Mutex) to guard the critical section.
• Limited Resources Control: Access to the limited coffee machines (maximum 2 concurrent users) is securely managed using a Semaphore(2).
• Inventory Management (Monitor Structure): Built using Java's implicit monitor synchronization mechanism (synchronized, wait(), and notifyAll()). Baristas wait if ingredients are low, and a dedicated Supplier thread automatically refills the stock safely.

2. Advanced Logging System (Bonus Section - IPC via Sockets)

• A decoupled, standalone process (LoggerProcess) acts as a localized log server.
• The main simulation communicates with the Logger process using Network Sockets as an Inter-Process Communication (IPC) mechanism.
• Every system event is captured synchronously, displayed elegantly in the server terminal, and persistently appended to cafe_system.log.

---

Project Structure

cafe_simulation/
│
├── src/
│   └── cafe/
│       ├── concurrency/     # OrderQueue, Inventory, CoffeeMachine (Monitors & Semaphores)
│       ├── logger/          # LoggerProcess (Independent IPC Logger Server)
│       ├── models/          # Order, DrinkType
│       ├── threads/         # Barista, OrderGenerator, Supplier
│       └── Main.java        # Core Application Entry Point
│
├── cafe_system.log          # Persisted output log file
└── README.md                # Project documentation

How to Run the Project

Follow these steps exactly in your terminal to execute the simulation smoothly:

Step 1: Compile the Project

Open a command prompt or terminal in the project's root directory (cafe_simulation) and run the following command to compile all source files:

javac src\cafe\models\*.java src\cafe\concurrency\*.java src\cafe\threads\*.java src\cafe\logger\*.java src\cafe\*.java

Step 2: Start the Logger Process (Server)

Launch the standalone logger process in your first terminal window. This process will spin up and listen on port 27805:

java -cp src cafe.logger.LoggerProcess

Expected output: [Logger Process] Listening on port 27805...

Step 3: Run the Cafe Simulation (Client)

Without closing the first terminal, open a second terminal tab or window (+ in VS Code Terminal) in the same directory and execute the main simulation:

java -cp src cafe.Main

Expected Output

Once Main is executed, the Logger terminal will stream real-time concurrency events detailing order creation, enqueueing/dequeueing, ingredient withdrawals, coffee machine locks, and deliveries.

At the end of the simulation, the system automatically shuts down gracefully and prints a clean final synchronization report:

--- Starting Cafe Order Management Simulator ---

==============================================
       Final Cafe System Report       
==============================================
Total Orders Generated: 50
Total Orders Processed: 50
Remaining Orders in Queue: 0
Final Inventory Status: Coffee: 64, Milk: 0, Cups: 100
Total Coffee Machine Usages: 43
System Integrity Check: PASSED (No race conditions detected)
==============================================

All recorded outputs will also be fully saved inside the cafe_system.log file.