WIP: infotainer

Infotainer contains building blocks for simple pubsub services based on actix/-web, cbor and websockets.

Components

• websocket interface: handles client-server interaction
• pubsub service: manages subscriptions and handles publication of client submissions
• datalog service: maintains log indices for and handles filesystem interactions
• session service: manages client sessions

The websocket interface is an actor whose handlers are largely built around the ClientCommand and ServerResponse types. ClientCommand consists of struct variants holding data sent from client to server. These are translated into actix Messages by the WebSocketSession actor.
The ServerResponse type is used to wrap data sent from server to client and can contain HashSet<Uuid>, representing a subscriptions log index, Publication, representing data published by some client, or DataLogEntry, containing one or more Publications previously submitted to the data log.

The pubsub service actor handles the SubmitCommand and ManageSubscription messages. When data is submitted for publication, the actor looks up the addressed Subscription, generates a Publication, sends it, wrapped in a DataLogPut message, to the DataLogger and proceeds to distribute it to connected clients subscribed to the Subscription.
ManageSubscription has two variants, Add and Remove, and is used by clients to un-/subscribe from/to Subscriptions.

DatalogService enables persisting the server state as well as published data. DataLogPut messages represent write requests for SubscriptionMeta, subscriber lists and Publications. DataLogFetch messages are used to retrieve persisted data. Additionally, it maintains a log of subscriptions and their publications.

The SessionService actor is a client registry, representing active sessions in a HashMap<Uuid, Addr<WebSocketSession>> and provides messages for clients to un-/register themselves as well as a message for other actors to resolve a clients ID to its WebSocketSession actors Addr.

Features

• websocket interface/ client message types
• Subscription/Subscription table
• Broadcast-type subscriptions
• Queue-type subscriptions
• Publication
• publishing messages
• session management
• data log service
• persisting/retrieval of publication data
• persisting/retrieval of subscription metadata
• recreating server state from persisted data
• client service