Getting Started

1. Navigate to the Simulation Folder

   • Go to the experiment/simulation/ directory in your project workspace.

2. Open the Simulation

   • Locate the index.html file inside the simulation folder.
   • Open index.html in your preferred web browser (e.g., Chrome, Firefox).
   • You can do this by double-clicking the file or right-clicking and selecting "Open With" > your browser.

Understanding the Interface

The simulation interface consists of three main areas:

1. Control Panel (Left): Contains all buttons and controls
2. Experiment Area (Center): Visual representation of nodes and communication
3. Transaction Log (Right): Real-time log of all protocol activities

How to Use the Program

Basic Transaction Simulation

1. Start New Transaction

   • Click the "Start New Transaction" button to begin the simulation
   • This initializes a new two-phase commit protocol instance
   • The "Next Step" button becomes enabled

2. Step Through the Protocol

   • Click "Next Step" repeatedly to advance through each phase:
     • Phase 1 (Voting Phase):
       • Coordinator sends PREPARE messages to all participants
       • Each participant votes YES and enters PREPARED state
     • Phase 2 (Decision Phase):
       • Coordinator decides COMMIT based on unanimous YES votes
       • Coordinator sends COMMIT messages to all participants
       • Participants acknowledge and complete the transaction

3. Reset Simulation

   • Click "Reset Simulation" to return to the initial state
   • All nodes return to idle state and logs are cleared

Failure Simulation (Advanced)

4. Simulate Participant Failure (Phase 1)

   • Click this button during Phase 1 to simulate a random participant failing
   • Observe how the coordinator handles timeouts and decides to abort
   • Watch the protocol's response to unreachable participants

5. Simulate Coordinator Failure (Phase 1)

   • Click this button during Phase 1 to simulate coordinator failure
   • Participants enter "in-doubt" state (holding locks)
   • Demonstrates the blocking nature of 2PC

6. Simulate Participant Failure (Phase 2)

   • Click this button during Phase 2 to simulate participant failure during commit
   • Shows how participants can recover and complete delayed commits

7. Simulate Coordinator Failure (Phase 2)

   • Click this button during Phase 2 to simulate the most critical failure scenario
   • Some participants may commit while others remain blocked
   • Demonstrates potential consistency issues

8. Simulate Recovery

   • Click this button to recover failed nodes
   • Shows how the protocol handles recovery using transaction logs
   • Resolves in-doubt and blocked participants

Understanding Visual Elements

• Blue Circle (Center): Coordinator node
• Smaller Blue Circles: Participant nodes (P1, P2, P3, P4)
• Animated Lines: Communication channels between nodes
• Message Bubbles: Protocol messages (PREPARE, YES/NO, COMMIT, ABORT)
• Node Colors:
  • Blue: Normal/Ready state
  • Green: Voted YES or Committed
  • Orange: Voted NO
  • Red: Failed node
  • Blinking: In-doubt state
  • Gray: Aborted

Observing Protocol Behavior

1. Transaction Log (Right Panel)

   • Monitor real-time protocol activities
   • Observe message exchanges and state changes
   • Track failure scenarios and recovery procedures

2. Phase Indicator (Top-Right of Center)

   • Shows current protocol phase
   • Updates as simulation progresses

3. Connection Lines

   • Solid lines: Normal communication
   • Broken/dashed lines: Failed communication
   • Animated lines: Active message transmission

Troubleshooting

• If the simulation does not load, ensure your browser supports HTML5 and JavaScript
• Check that all files in the simulation folder are present and not corrupted
• For best experience, use a modern browser (Chrome, Firefox, Safari, Edge)