Whatsup

1 to 1 messaging

group messaging

media handling

Websocket server maintains lifecycle of the websocket connection. All they know is that they have a connection and they have to go to chat service.

Websocket manager. Once user opens an app it establishes Websocket connection to Webserver. And then hits REST API of WebSocket manager saying I am a user and I have gateway id.

Chat service.

User send a message. Message is stored in Cassandra and user gets a notification that message is received.