systemprompt-events

Event broadcasting and routing infrastructure for SSE (Server-Sent Events) connections.

Overview

This crate provides a type-safe, generic event broadcasting system for real-time communication with connected clients. It manages connection lifecycles, routes events to appropriate channels, and handles automatic cleanup of disconnected clients.

File Structure

crates/infra/events/
├── Cargo.toml
├── README.md
├── status.md
└── src/
    ├── lib.rs                      # 27 lines  - Trait definitions, type aliases, re-exports
    └── services/
        ├── mod.rs                  # 10 lines  - Module re-exports
        ├── broadcaster.rs          # 191 lines - GenericBroadcaster implementation
        └── routing.rs              # 51 lines  - EventRouter, global singletons

Modules

`lib.rs`

Entry point defining core abstractions:

Broadcaster trait - Type-safe async broadcasting with connection management
EventSender type alias - Channel sender for SSE events (UnboundedSender<Result<Event, Infallible>>)

`services/broadcaster.rs`

Generic broadcaster implementation:

GenericBroadcaster<E> - Thread-safe broadcaster using Arc<RwLock<HashMap<UserId, HashMap<ConnId, Sender>>>>
ConnectionGuard<E> - RAII guard for automatic connection cleanup on drop
Type aliases: AgUiBroadcaster, A2ABroadcaster, ContextBroadcaster, AnalyticsBroadcaster
Keep-alive utilities: standard_keep_alive(), HEARTBEAT_INTERVAL, HEARTBEAT_JSON

`services/routing.rs`

Event routing and global state:

EventRouter - Routes events to appropriate broadcaster(s)
Global singletons: AGUI_BROADCASTER, A2A_BROADCASTER, CONTEXT_BROADCASTER, ANALYTICS_BROADCASTER

Public API

Traits

Trait	Methods	Purpose
`Broadcaster`	`register`, `unregister`, `broadcast`, `connection_count`, `total_connections`	Type-safe event broadcasting

Types

Type	Description
`EventSender`	`UnboundedSender<Result<Event, Infallible>>`
`GenericBroadcaster<E>`	Generic broadcaster for any `ToSse + Clone + Send + Sync` event
`AgUiBroadcaster`	`GenericBroadcaster<AgUiEvent>`
`A2ABroadcaster`	`GenericBroadcaster<A2AEvent>`
`ContextBroadcaster`	`GenericBroadcaster<ContextEvent>`
`AnalyticsBroadcaster`	`GenericBroadcaster<AnalyticsEvent>`
`ConnectionGuard<E>`	RAII guard for automatic unregistration
`EventRouter`	Routes events to appropriate broadcasters

Constants

Constant	Value	Purpose
`HEARTBEAT_INTERVAL`	15 seconds	SSE keep-alive interval
`HEARTBEAT_JSON`	`{"type":"heartbeat"}`	Keep-alive payload

Global Singletons

Static	Type	Purpose
`AGUI_BROADCASTER`	`LazyLock<AgUiBroadcaster>`	AG-UI event broadcasts
`A2A_BROADCASTER`	`LazyLock<A2ABroadcaster>`	Agent-to-agent events
`CONTEXT_BROADCASTER`	`LazyLock<ContextBroadcaster>`	Aggregated context events
`ANALYTICS_BROADCASTER`	`LazyLock<AnalyticsBroadcaster>`	Analytics event tracking

Event Flow

                    ┌─────────────────┐
                    │   EventRouter   │
                    └────────┬────────┘
                             │
        ┌────────────────────┼────────────────────┐
        │                    │                    │
        ▼                    ▼                    ▼
┌───────────────┐    ┌───────────────┐    ┌───────────────┐
│AGUI_BROADCASTER│    │A2A_BROADCASTER│    │CONTEXT_BROADCASTER│
└───────┬───────┘    └───────┬───────┘    └───────┬───────┘
        │                    │                    │
        ▼                    ▼                    ▼
   SSE Clients          SSE Clients          SSE Clients

AgUI and A2A events are routed to both their primary broadcaster AND the context broadcaster for aggregation.

Dependencies

Crate	Purpose
`systemprompt-models`	Event types (`AgUiEvent`, `A2AEvent`, `ContextEvent`, `SystemEvent`, `ToSse` trait)
`systemprompt-identifiers`	`UserId` type
`tokio`	Async runtime, channels, synchronization
`axum`	SSE `Event` and `KeepAlive` types
`async-trait`	Async trait support
`tracing`	Structured logging

Tests

Tests are located in crates/tests/unit/infra/events/ following the project convention of separating tests from source files.

systemprompt-events 0.0.1