SignalR Notification Contract
The Deck uses SignalR as a real-time notification layer. SignalR is not the source of truth; SQL storage is. SignalR tells connected dashboards that something changed and which UI areas should refresh or update.
Where It Lives
| Runtime type | Role |
|---|---|
IChokaQNotifier | Runtime notification contract. |
ChokaQSignalRNotifier | SignalR implementation that sends events to clients. |
ChokaQHub | Bidirectional hub for dashboard commands and live updates. |
Events
| Event | Meaning |
|---|---|
JobUpdated | Active job status changed. |
JobProgress | Handler reported progress. |
JobArchived | Job moved to successful history. |
JobFailed | Job moved to DLQ. |
JobResurrected | DLQ job moved back to active work. |
JobsPurged | Jobs were permanently deleted. |
QueueStateChanged | Queue pause/resume changed. |
StatsUpdated | Dashboard counters should refresh. |
Correctness Boundary
SignalR messages can be delayed, dropped by disconnects, or observed out of order by a browser. That is acceptable because the dashboard can always reload authoritative state from storage.
The event contract should be treated as a UI invalidation protocol, not as a durable event stream.
Architecture Decision
Why this pattern?
Operators need low-latency feedback when jobs move, fail, resurrect, or purge. SignalR fits interactive dashboard updates without adding a separate broker.
Trade-offs
SignalR requires connected clients and authorization on the hub. It does not replace storage reads or metrics. Dashboard code must tolerate reconnects and refresh from storage.
Alternatives considered
| Alternative | Benefit | Cost |
|---|---|---|
| Polling only | Simple and robust. | Slower operator feedback and more periodic reads. |
| External pub/sub | Durable fanout possible. | Extra infrastructure for dashboard invalidation. |
| Browser refresh only | Minimal code. | Poor incident workflow. |
Additional Questions
Is SignalR authoritative?
No. SQL is authoritative. SignalR is a notification and invalidation layer.
What happens if a client misses an event?
The next refresh or explicit storage query returns authoritative state.
Why not use a broker?
For dashboard invalidation, SignalR is enough and avoids adding infrastructure.