midi-harbor/specs/009-observability/data-model.md

Data Model: Observability

Part of the domain model; identity and the endpoint are shared by every spec. Types live in midi-harbor-core unless noted.

---

TrafficCounters (FR-045)

TrafficCounters {
    messages_sent:      u64
    messages_received:  u64
    bytes_sent:         u64
    bytes_received:     u64
    messages_lost:      u64    // detected via RTP sequence gaps
    messages_recovered: u64    // restored from the recovery journal
    messages_dropped:   u64    // ring buffer overflow — our own backpressure
    last_activity:      Option<Timestamp>
}

All fields are atomics incremented on the real-time path with no logging or allocation (Principle III). messages_dropped is deliberately distinct from messages_lost: one is our backpressure, the other is the network's.

---

Event (FR-046, Principle VII)

Event {
    id:        EventId        // monotonic
    at:        Timestamp
    endpoint:  Option<EndpointId>
    route:     Option<RouteId>
    severity:  Severity       // Info | Warning | Error
    kind:      EventKind       // stable, machine-readable name
    detail:    String          // human-readable
}

Retained in a bounded in-memory ring (default 10,000 events) that survives GUI restarts because it lives in the daemon (FR-046). Not persisted across daemon restarts — deliberately, to bound disk use; the diagnostic export (FR-048) is the durable artifact.