# Message Bus

## Overview
The Message Bus service will provide the central event-driven communication infrastructure for the stock-bot platform. It will enable reliable, scalable, and decoupled interaction between services through asynchronous messaging, event streaming, and publish-subscribe patterns.

## Planned Features

### Messaging Infrastructure
- **Topic-based Messaging**: Publish-subscribe communication model
- **Message Queuing**: Reliable message delivery with persistence
- **Event Streaming**: Real-time event processing with replay capabilities
- **Message Routing**: Dynamic routing based on content and metadata
- **Quality of Service**: Various delivery guarantee levels (at-least-once, exactly-once)

### Message Processing
- **Message Transformation**: Content transformation and enrichment
- **Message Filtering**: Rules-based filtering of messages
- **Schema Validation**: Enforcement of message format standards
- **Serialization Formats**: Support for JSON, Protocol Buffers, Avro
- **Compression**: Message compression for efficiency

### Operational Features
- **Dead Letter Handling**: Management of unprocessable messages
- **Message Tracing**: End-to-end tracing of message flow
- **Event Sourcing**: Event storage and replay capability
- **Rate Limiting**: Protection against message floods
- **Back-pressure Handling**: Flow control mechanisms

### Integration Capabilities
- **Service Discovery**: Dynamic discovery of publishers/subscribers
- **Protocol Bridging**: Support for multiple messaging protocols
- **External System Integration**: Connectors for external message systems
- **Legacy System Adapters**: Integration with non-event-driven systems
- **Web Integration**: WebSocket and SSE support for web clients

## Planned Integration Points

### Service Connections
- All platform microservices as publishers and subscribers
- Trading Dashboard (for real-time updates)
- External Data Sources (for ingestion)
- Monitoring Systems (for operational events)

## Planned Technical Implementation

### Technology Stack
- **Messaging Platform**: Kafka or RabbitMQ
- **Client Libraries**: Native TypeScript SDK
- **Monitoring**: Prometheus integration for metrics
- **Management**: Admin interface for topic/queue management
- **Storage**: Optimized storage for event persistence

### Architecture Pattern
- Event-driven architecture
- Publish-subscribe pattern
- Command pattern for request-response
- Circuit breaker for resilience

## Development Guidelines

### Message Design
- Event schema standards
- Versioning approach
- Backward compatibility requirements
- Message size considerations

### Integration Patterns
- Event notification pattern
- Event-carried state transfer
- Command messaging pattern
- Request-reply pattern implementations

### Operational Considerations
- Monitoring requirements
- Scaling guidelines
- Disaster recovery approach
- Message retention policies

## Implementation Roadmap
1. Core messaging infrastructure
2. Service integration patterns
3. Operational tooling and monitoring
4. Advanced features (replay, transformation)
5. External system connectors and adapters