Proposal: PubSub Architecture for relay

[yuki-uchida]

Discussion

current sequence is here.
But, now we can't cascade moq-wasm server, So we need to re-architecture for cascading.

I propose new architecture for cascading relay.

sequenceDiagram
    participant Producer(Client)
    participant Consumer(Server)
    participant Producer(Server)
    participant Consumer(Client)

    Producer(Client) ->> Consumer(Server): CLIENT_SETUP
    activate Consumer(Server)
    Consumer(Server) ->> Producer(Client): SERVER_SETUP
    Consumer(Client) ->> Producer(Server): CLIENT_SETUP
    activate Producer(Server)
    Producer(Server) ->> Consumer(Client): SERVER_SETUP

    Producer(Client) ->> Consumer(Server): ANNOUNCE
    Consumer(Server) ->> Producer(Client): ANNOUNCE_OK
    Consumer(Server) -->> Producer(Server): Forward<br/> TrackNamespace

    Note over Producer(Client), Consumer(Client) : ANNOUNCE for Consumer (Client)
        alt Consumer(Client) needs ANNOUNCE of a specific TrackNamespace
        Consumer(Client) ->> Producer(Server): SUBSCRIBE_NAMESPACE
        Producer(Server) ->> Consumer(Client): SUBSCRIBE_NAMESPACE_OK
        alt exists the TrackNamespace matches to the Prefix 
            Producer(Server) ->> Consumer(Client): ANNOUNCE
            Consumer(Client) ->> Producer(Server): ANNOUNCE_OK
        end

        alt updates the TrackNamespace matches to the Prefix 
    Producer(Client) ->> Consumer(Server): ANNOUNCE
    Consumer(Server) ->> Producer(Client): ANNOUNCE_OK
    Consumer(Server) -->> Producer(Server): Forward<br/> TrackNamespace
            Producer(Server) ->> Consumer(Client): ANNOUNCE
            Consumer(Client) ->> Producer(Server): ANNOUNCE_OK
        end
    end

    Note over Producer(Client), Consumer(Client) : Branched by timing of SUBSCRIBE
    alt already server subscribed
        Consumer(Server) ->> Producer(Client): SUBSCRIBE
        Producer(Client) ->> Consumer(Server): SUBSCRIBE_OK
        Consumer(Server) -->> Producer(Server): Forward TrackName
        Consumer(Client) ->> Producer(Server): SUBSCRIBE
        Producer(Server) ->> Consumer(Client): SUBSCRIBE_OK
    else not already server subscribed
        Consumer(Client) ->> Producer(Server): SUBSCRIBE
        Producer(Server) -->> Consumer(Server): Request Subscribe
        Consumer(Server) ->> Producer(Client): SUBSCRIBE
        Producer(Client) ->> Consumer(Server): SUBSCRIBE_OK
        Consumer(Server) -->> Producer(Server): Response Subscribe completed
        Producer(Server) ->> Consumer(Client): SUBSCRIBE_OK
    end

    Note over Producer(Client), Consumer(Client) : Data Stream Phase

    loop
        Producer(Client) ->> Consumer(Server): OBJECT
        Consumer(Server) -->> Producer(Server): Cache and Forward
        Producer(Server) ->> Consumer(Client): OBJECT
    end

    Note over Producer(Client), Consumer(Client) : End Phase

   alt by End Subscriber
        Consumer(Client) ->> Producer(Server): UNSUBSCRIBE
        Producer(Server) -->> Consumer(Server): Notify
        Note over Consumer(Server), Producer(Client): if needed
        Consumer(Server) ->> Producer(Client): UNSUBSCRIBE
  end 
  alt by Original Publisher
        Producer(Client) ->> Consumer(Server): SUBSCRIBE_DONE
        Consumer(Server) -->> Producer(Server): Request Stop Specific Subscription
        Producer(Server) ->> Consumer(Client): SUBSCRIBE_DONE
  end 
  alt if Scheduled to end
        Producer(Client) ->> Consumer(Server): UNANNOUNCE
        Consumer(Server) -->> Producer(Server): Request Stop New Subscription
        Consumer(Server) ->> Producer(Client): ANNOUNCE_CANCEL
Producer(Client) ->> Consumer(Server): SUBSCRIBE_DONE
        Consumer(Server) -->> Producer(Server): Request Stop Subscription
        Producer(Server) ->> Consumer(Client): SUBSCRIBE_DONE
   end 

    deactivate Consumer(Server)
    deactivate Producer(Server)

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