Module topology 

Room-local routed topology and media placement lifetimes.

Router coordinates user sessions across one or more routers. Each user holds a Home Session on their assigned placement router where their published producers live.

Cross-Router Routing & Foreign Shadows

When User 2 (placed on Router 2) subscribes to User 1’s producer (published on Router 1):

1. Producer P1 lives on Router 1.
2. Router 1 uses a Foreign Session Shadow for User 2 (using User 2’s connection ID), creating it only when absent.
3. Consumer C2 is created inside this shadow session on Router 1, attached directly to Producer P1.
4. The router records the C2-to-P1 dependency and o-sfu-core forwards to User 2’s media worker.

  RouterId 1 (Publisher Placement)                RouterId 2 (Subscriber Placement)
+------------------------------------+          +------------------------------------+
| Home Session (User 1):             |          | Home Session (User 2):             |
|   Producer P1 dependent IDs:       |          |   Connection Conn_2                |
|     |                              |          |     ^                              |
|     +--> C1 (User 3 home session)  |          |     |                              |
|     |                              |          |     |                              |
|     +--> C2 dependency             |          |     |                              |
|          (Conn_2 foreign shadow)   | -------->|-----+ (Core forwards to worker)    |
+------------------------------------+          +------------------------------------+

Lifecycle & Cascade Teardowns:
  - Producer P1 Removed (`Router::remove_producer`):
    -> Cascades down to remove local C1 and foreign C2 on Router 1.
    -> The shadow session for Conn_2 becomes empty and is automatically pruned.
  - User 2 Disconnects / Replaces Connection:
    -> Removes User 2's Home Session on Router 2.
    -> Removes C2 from P1's dependents and prunes the foreign shadow on Router 1.
    -> User 1's Producer P1 and local Consumer C1 remain active and unaffected.

Structs

CommittedSession 🔒

LocalRouter 🔒

LocalSession 🔒

PlacementSnapshot

RoutedConsumerId

consumer identity plus its source router and receiver connection

RoutedProducerId

producer identity plus its source router and connection

Router

pure room router for placement and routed media lifetimes

RouterPlacement

RouterPlacements

Enums

RouterPlacementsError