tasq/node_modules/@claude-flow/shared/docs/EVENTS_README.md

Event Store Persistence (ADR-007)

Complete event sourcing implementation for V3 Claude Flow with persistent storage, projections, and event replay.

Overview

The Event Store provides a robust foundation for tracking all state changes in the V3 system through domain events. This enables:

• Complete Audit Trail: Every state change is recorded
• Time Travel: Replay events to reconstruct state at any point
• Projections: Build multiple read models from the same events
• Debugging: Understand exactly what happened and when
• Event-Driven Architecture: Decouple components through events

Architecture

┌─────────────────────────────────────────────────────────────┐
│                      Event Store                            │
│  ┌───────────────────────────────────────────────────────┐  │
│  │  SQLite Database (sql.js for cross-platform)          │  │
│  │  - events table (append-only log)                     │  │
│  │  - snapshots table (performance optimization)         │  │
│  └───────────────────────────────────────────────────────┘  │
└─────────────────────────────────────────────────────────────┘
           │                    │                    │
           ▼                    ▼                    ▼
    ┌──────────────┐   ┌──────────────┐   ┌──────────────┐
    │   Agent      │   │    Task      │   │   Memory     │
    │ Projection   │   │  Projection  │   │ Projection   │
    └──────────────┘   └──────────────┘   └──────────────┘

Features

1. Event Store

• Persistent Storage: SQLite with sql.js fallback for Windows compatibility
• Versioning: Automatic version tracking per aggregate
• Filtering: Query events by type, aggregate, timestamp
• Replay: Iterate through all events for rebuilding state
• Snapshots: Performance optimization for large event streams
• Auto-Persist: Configurable auto-save to disk

2. Domain Events

Comprehensive event types for all aggregates:

Agent Events:

• agent:spawned - Agent created
• agent:started - Agent began working
• agent:stopped - Agent finished
• agent:failed - Agent encountered error
• agent:status-changed - Agent status updated
• agent:task-assigned - Task assigned to agent
• agent:task-completed - Agent completed task

Task Events:

• task:created - New task created
• task:started - Task execution began
• task:completed - Task finished successfully
• task:failed - Task failed
• task:blocked - Task blocked by dependencies
• task:queued - Task added to queue

Memory Events:

• memory:stored - Memory entry saved
• memory:retrieved - Memory entry accessed
• memory:deleted - Memory entry removed
• memory:expired - Memory entry expired

Swarm Events:

• swarm:initialized - Swarm started
• swarm:scaled - Agent count changed
• swarm:terminated - Swarm shut down
• swarm:phase-changed - Execution phase changed
• swarm:milestone-reached - Milestone achieved
• swarm:error - Swarm-level error

3. Projections

Build queryable read models from events:

AgentStateProjection:

• Current state of all agents
• Filter by status, domain, role
• Track task completion metrics
• Monitor agent health

TaskHistoryProjection:

• Complete task execution history
• Filter by status, agent, type
• Calculate average durations
• Track success/failure rates

MemoryIndexProjection:

• Memory access patterns
• Track usage by namespace
• Identify hot/cold data
• Monitor memory consumption

Usage

Basic Event Storage

import { EventStore, createAgentSpawnedEvent } from '@claude-flow/shared/events';

// Initialize
const eventStore = new EventStore({
  databasePath: './events.db',
  verbose: true,
});
await eventStore.initialize();

// Record events
const event = createAgentSpawnedEvent(
  'agent-1',
  'coder',
  'core',
  ['coding', 'testing']
);
await eventStore.append(event);

// Query events
const agentEvents = await eventStore.getEvents('agent-1');
const allTaskEvents = await eventStore.query({
  aggregateTypes: ['task']
});

// Cleanup
await eventStore.shutdown();

Using Projections

import {
  EventStore,
  AgentStateProjection,
  TaskHistoryProjection
} from '@claude-flow/shared/events';

const eventStore = new EventStore({ databasePath: './events.db' });
await eventStore.initialize();

// Build agent state projection
const agentProjection = new AgentStateProjection(eventStore);
await agentProjection.initialize();

// Query agent state
const activeAgents = agentProjection.getAgentsByStatus('active');
const agent1 = agentProjection.getAgent('agent-1');

console.log(`Active agents: ${activeAgents.length}`);
console.log(`Agent 1 completed ${agent1.completedTasks.length} tasks`);

// Build task history projection
const taskProjection = new TaskHistoryProjection(eventStore);
await taskProjection.initialize();

// Query task history
const completedTasks = taskProjection.getTasksByStatus('completed');
const avgDuration = taskProjection.getAverageTaskDuration();

console.log(`Completed: ${completedTasks.length} tasks`);
console.log(`Average duration: ${avgDuration}ms`);

Event Replay

// Replay all events
for await (const event of eventStore.replay()) {
  console.log(`${event.type} at ${new Date(event.timestamp)}`);
}

// Replay from specific version
for await (const event of eventStore.replay(100)) {
  // Process events starting from version 100
}

Snapshots

// Save snapshot for performance
await eventStore.saveSnapshot({
  aggregateId: 'agent-1',
  aggregateType: 'agent',
  version: 500,
  state: { status: 'active', tasks: ['task-1', 'task-2'] },
  timestamp: Date.now(),
});

// Load snapshot
const snapshot = await eventStore.getSnapshot('agent-1');
if (snapshot) {
  // Resume from snapshot version
  const events = await eventStore.getEvents('agent-1', snapshot.version);
}

Configuration

const eventStore = new EventStore({
  // Database path (:memory: for in-memory only)
  databasePath: './v3-events.db',

  // Enable verbose logging
  verbose: true,

  // Auto-persist interval (0 = manual only)
  autoPersistInterval: 5000, // 5 seconds

  // Recommend snapshots every N events
  snapshotThreshold: 100,

  // Custom sql.js WASM path (optional)
  wasmPath: './sql-wasm.wasm',
});

Performance

Indexing

The Event Store automatically creates indexes for:

• Aggregate ID + Version (unique)
• Aggregate Type
• Event Type
• Timestamp
• Version

Snapshots

Recommended usage:

• Save snapshot every 100-500 events
• Use snapshots for long-running aggregates
• Snapshots reduce replay time from O(n) to O(1)

Auto-Persist

• Default: 5 seconds
• In-memory mode: No persistence
• Disk mode: Periodic writes to SQLite file

Testing

Run comprehensive tests:

# Run all event store tests
npm test -- event-store.test.ts

# Run specific test suite
npm test -- event-store.test.ts -t "Event Appending"

Example

See example-usage.ts for a complete demonstration:

npx tsx v3/@claude-flow/shared/src/events/example-usage.ts

Output includes:

• Event recording
• Query examples
• Projection building
• Event replay
• Snapshots
• Statistics

Integration with V3

Agent Lifecycle

// Queen coordinator spawns agents
await eventStore.append(
  createAgentSpawnedEvent('agent-2', 'security-architect', 'security', ['auditing'])
);

// Track agent execution
await eventStore.append(createAgentStartedEvent('agent-2'));
await eventStore.append(createAgentTaskAssignedEvent('agent-2', 'task-1', Date.now()));

Task Execution

// Create task
await eventStore.append(
  createTaskCreatedEvent('task-1', 'security-audit', 'CVE-1 Fix', 'Fix injection', 'critical', [])
);

// Track progress
await eventStore.append(createTaskStartedEvent('task-1', 'agent-2'));
await eventStore.append(createTaskCompletedEvent('task-1', { fixed: true }, 5000));

Memory Operations

// Track memory usage
await eventStore.append(
  createMemoryStoredEvent('mem-1', 'agent-context', 'agent-2-state', 'episodic', 2048)
);

await eventStore.append(
  createMemoryRetrievedEvent('mem-1', 'agent-context', 'agent-2-state', 1)
);

Cross-Platform Compatibility

The Event Store uses sql.js for cross-platform SQLite support:

• Windows: Pure JavaScript/WASM (no native compilation)
• macOS: Works with standard Node.js
• Linux: Full compatibility

Database files are portable across platforms.

Migration Path

To integrate Event Store into existing V3 code:

1. Initialize Event Store: Add to swarm initialization
2. Record Events: Emit events on state changes
3. Build Projections: Replace direct state queries
4. Event Replay: Use for debugging and analytics
5. Snapshots: Add for performance optimization

ADR Compliance

This implementation fulfills ADR-007 requirements:

✅ Event Store with append(), getEvents(), getEventsByType(), replay() ✅ Domain events for agent, task, memory, swarm ✅ Projections for AgentState, TaskHistory, MemoryIndex ✅ SQLite persistence with cross-platform support ✅ Event versioning and snapshots ✅ Comprehensive test coverage

Contributing

When adding new domain events:

1. Define event interface in domain-events.ts
2. Add factory function
3. Update projections to handle new event
4. Add tests
5. Update this README

License

Part of claude-flow V3 - See root LICENSE file.