Snapshots

Snapshots are automatic copies of the model state that Multisynq saves to the cloud. This system provides seamless persistence and enables new users to join existing sessions efficiently without replaying the entire event history.

What Are Snapshots?

📸 Snapshot Definition

Snapshots are serialized copies of your complete model state, saved periodically to the cloud. They capture:

All model properties and data
Current object relationships
Session state at a specific moment
Everything needed to restore the exact state

Snapshots are taken automatically by the Multisynq system - you don’t need to manually create them.

How Snapshots Work

Automatic Creation

The Multisynq reflector periodically requests one of the session participants to create a snapshot of the current model state.

// This happens automatically - no code needed
// The system serializes your entire model state

Cloud Storage

The snapshot is compressed and stored in the cloud, associated with your session ID.

// Snapshots are stored with metadata:
// - Session ID
// - Timestamp
// - Model state hash
// - Event sequence number

Restoration

When needed, the snapshot is loaded and your model state is restored exactly as it was.

// Your model's init() method won't be called
// The state is restored directly from the snapshot

Snapshot Use Cases

🔄 Session Persistence
🚀 New User Synchronization

Automatic save functionality for your applicationWhen users quit or reload:

Session state is preserved in the latest snapshot
When they return, the exact state is restored
No progress is lost

// Example: Game state preservation
class GameModel extends Multisynq.Model {
    init() {
        this.level = 1;
        this.score = 0;
        this.playerPositions = new Map();
    }
    
    // All of this state is automatically saved in snapshots
    // and restored when the session resumes
}

New User Join Process

1. Snapshot Loading

The local model is initialized with data from the last snapshot

// Instead of calling init(), your model is restored from snapshot
// This bypasses normal initialization
class GameModel extends Multisynq.Model {
    init() {
        // This WON'T be called for users joining from snapshot
        console.log("Fresh session start");
    }
}

Your model’s init() method is NOT called when loading from a snapshot.

2. Event Replay

The reflector resends all events transmitted after the snapshot

// All events since the snapshot are replayed
// This brings the snapshot up to the current state
// Events are processed in the exact same order

Event replay is deterministic - the same events produce the same results.

3. Model Simulation

The model simulates all events to bring the snapshot up-to-date

// Your model processes all missed events
// This happens automatically and synchronously
// The model becomes current with other users

4. View Initialization

The local view initializes to match the model state

class GameView extends Multisynq.View {
    init() {
        // This IS called for snapshot joins
        // Your view should be prepared to handle existing state
        this.canvas = document.getElementById('canvas');
        
        // The model may already have data from the snapshot
        this.displayExistingPlayers();
    }
    
    displayExistingPlayers() {
        // Handle the case where players already exist
        for (const player of this.model.players.values()) {
            this.createPlayerVisual(player);
        }
    }
}

View Initialization Considerations

Important: When writing your View initialization, account for the fact that the Model may have been restored from a snapshot and already contains data.

❌ Problematic Approach
✅ Correct Approach

class GameView extends Multisynq.View {
    init() {
        this.players = new Map();
        
        // This assumes the model starts empty
        // But it might already have players from a snapshot!
        this.subscribe("player", "joined", this.addPlayer);
    }
    
    addPlayer(player) {
        this.players.set(player.id, new PlayerVisual(player));
    }
    
    // Missing: handling existing players from snapshot
}

class GameView extends Multisynq.View {
    init() {
        this.players = new Map();
        
        // Handle existing players from snapshot
        this.initializeExistingPlayers();
        
        // Subscribe to future player events
        this.subscribe("player", "joined", this.addPlayer);
        this.subscribe("player", "left", this.removePlayer);
    }
    
    initializeExistingPlayers() {
        // Check if model already has players (from snapshot)
        for (const player of this.model.players.values()) {
            this.createPlayerVisual(player);
        }
    }
    
    createPlayerVisual(player) {
        const visual = new PlayerVisual(player);
        this.players.set(player.id, visual);
    }
    
    addPlayer(player) {
        this.createPlayerVisual(player);
    }
    
    removePlayer(playerId) {
        const visual = this.players.get(playerId);
        if (visual) {
            visual.destroy();
            this.players.delete(playerId);
        }
    }
}

Snapshot Performance

Current Limitation: The snapshot system is currently unoptimized and may cause performance hitches when snapshots are taken.

🐌 Current Behavior
🔄 Mitigation Strategies

Performance hitch: Brief pause when snapshot is taken
Visible to users: May notice application freeze
Depends on model size: Larger models = longer pause

// During snapshot creation:
// 1. Model state is serialized
// 2. Data is compressed
// 3. Snapshot is transmitted
// 4. Normal execution resumes

Until the system is optimized, you can:

Keep models lean: Avoid storing unnecessary data
Use efficient data structures: Prefer simple objects over complex ones
Clean up regularly: Remove unused objects
Monitor model size: Be aware of your state footprint

class OptimizedModel extends Multisynq.Model {
    init() {
        // Use efficient data structures
        this.players = new Map(); // Better than array for lookups
        this.cleanup();
    }
    
    cleanup() {
        // Regularly clean up unused data
        this.future(10000).cleanup();
        
        // Remove expired objects
        for (const [id, player] of this.players) {
            if (player.isExpired()) {
                this.players.delete(id);
            }
        }
    }
}

Best Practices

📊 Model Design

Keep your model state snapshot-friendly

Use simple, serializable data types
Avoid circular references
Keep the state tree flat when possible
Clean up unused objects regularly

// Good for snapshots
this.score = 100;
this.players = new Map();
this.gameState = "active";

// Avoid complex nested structures
this.deepNestedData = {...};

🎨 View Initialization

Design views to handle existing state

Check for existing model data in init()
Create visuals for pre-existing objects
Subscribe to future events
Handle both fresh starts and snapshot loads

init() {
    // Handle snapshot case
    this.initializeExistingState();
    
    // Handle future events
    this.subscribeToEvents();
}

🧪 Testing

Test your snapshot behavior

Test fresh session starts
Test joining existing sessions
Verify state restoration
Check view initialization

// Test both scenarios:
// 1. Fresh session (init() called)
// 2. Snapshot join (init() not called)

⚡ Performance

Optimize for snapshot performance

Monitor your model size
Use efficient data structures
Clean up regularly
Avoid storing view-specific data in models

// Good: Store only essential state
this.gameLogic = essentialData;

// Bad: Store view-specific data
this.uiElements = domElements;

Debugging Snapshots

Snapshot Detection
State Validation

Detect if your model loaded from a snapshot

class GameModel extends Multisynq.Model {
    init() {
        // This only runs for fresh sessions
        this.fromSnapshot = false;
        console.log("Fresh session start");
    }
    
    // Called after snapshot restore OR fresh init
    start() {
        if (!this.fromSnapshot) {
            this.fromSnapshot = true;
            console.log("Loaded from snapshot");
        }
    }
}

Verify snapshot state is correct

class GameModel extends Multisynq.Model {
    validateState() {
        // Check state integrity after snapshot load
        console.log("Players:", this.players.size);
        console.log("Game state:", this.gameState);
        console.log("Score:", this.score);
        
        // Verify relationships
        for (const player of this.players.values()) {
            if (!player.isValid()) {
                console.error("Invalid player state:", player);
            }
        }
    }
}

Common Patterns

🎮 Game State Snapshots

Preserving game progress across sessions

class GameModel extends Multisynq.Model {
    init() {
        // Fresh game start
        this.level = 1;
        this.score = 0;
        this.players = new Map();
        this.gameState = "waiting";
        this.startTime = Date.now();
    }
    
    // All this state is automatically preserved
    // When users rejoin, they continue exactly where they left off
}

class GameView extends Multisynq.View {
    init() {
        // Handle both fresh starts and snapshot resumes
        this.initializeUI();
        this.displayCurrentState();
    }
    
    displayCurrentState() {
        // Show current level, score, etc.
        this.updateScore(this.model.score);
        this.updateLevel(this.model.level);
        
        // Display existing players
        for (const player of this.model.players.values()) {
            this.createPlayerDisplay(player);
        }
    }
}

💬 Chat History

Preserving conversation history

class ChatModel extends Multisynq.Model {
    init() {
        this.messages = [];
        this.users = new Map();
    }
    
    addMessage(message) {
        this.messages.push(message);
        
        // Keep only last 100 messages for snapshot efficiency
        if (this.messages.length > 100) {
            this.messages.shift();
        }
    }
}

class ChatView extends Multisynq.View {
    init() {
        this.chatContainer = document.getElementById('chat');
        
        // Display existing messages from snapshot
        this.displayMessageHistory();
        
        // Subscribe to new messages
        this.subscribe("chat", "message", this.displayMessage);
    }
    
    displayMessageHistory() {
        for (const message of this.model.messages) {
            this.displayMessage(message);
        }
    }
}

Future Improvements

The Multisynq development team is working to make snapshots invisible to both users and developers:

Invisible performance: No more hitches during snapshot creation
Optimized storage: Smaller snapshots, faster loading
Better compression: Reduced network overhead
Incremental snapshots: Only save changes since last snapshot

Next Steps

Persistence

Learn about explicit persistence beyond snapshots

Writing a Multisynq Model

Master model development for snapshot-friendly code

Writing a Multisynq View

Learn to handle both fresh starts and snapshot loads

Sim Time & Future

Understand time-based behaviors in snapshotted sessions

Snapshots are fundamental to Multisynq’s persistence and scalability. Understanding how they work will help you design better models and views that handle session continuity seamlessly.

Get Started

Tutorials

Conceptual

Essentials

AI Development

What Are Snapshots?

📸 Snapshot Definition

How Snapshots Work

Snapshot Use Cases

New User Join Process

View Initialization Considerations

Snapshot Performance

Best Practices

📊 Model Design

🎨 View Initialization

🧪 Testing

⚡ Performance

Debugging Snapshots

Common Patterns

Future Improvements

Next Steps

Persistence

Writing a Multisynq Model

Writing a Multisynq View

Sim Time & Future

Get Started

Tutorials

Conceptual

Essentials

AI Development

​What Are Snapshots?

📸 Snapshot Definition

​How Snapshots Work

​Snapshot Use Cases

​New User Join Process

​View Initialization Considerations

​Snapshot Performance

​Best Practices

📊 Model Design

🎨 View Initialization

🧪 Testing

⚡ Performance

​Debugging Snapshots

​Common Patterns

​Future Improvements

​Next Steps

Persistence

Writing a Multisynq Model

Writing a Multisynq View

Sim Time & Future

What Are Snapshots?

How Snapshots Work

Snapshot Use Cases

New User Join Process

View Initialization Considerations

Snapshot Performance

Best Practices

Debugging Snapshots

Common Patterns

Future Improvements

Next Steps