If such and such an event occurred in the database, how to tell it to such and such clients and perform such and such actions?

Question

Node.js

Hello. I decided to get acquainted with node.js, mongodb and websockets, in connection with which I started developing a small resource. A duel is created between several players, when a new person enters the duel, his id is recorded in the database. Now you need to tell the rest of the participants in this duel that a new player has appeared and, accordingly, show this information to them (in simple terms: if such and such an event occurred in the database, say it to such and such clients and perform such and such actions). I'm dabbling in the direction of sockjs but I can't figure it out until the end. Experience, alas, is not enough and stalled on such a problem. In general, please tell me who than can, how to solve problems of such a plan.

Answer 1

As far as I understand, there are no rooms or any kind of routing out of the box in SockJS. Therefore, you will need to implement it yourself. The algorithm is something like this:
- a unique identifier is generated for each room
- clients in the room are assigned its identifier and a handler is assigned that subscribes to the corresponding pubsub channel in Redis.
- when connecting a new user, we push a message that a new user has connected to the room into the room channel (pubsub)
- handlers of each client receive a message and send it directly to the client
Alternatively, you can switch to something more functional, for example: faye or socket. io .

Answer 2

It's not entirely clear why Redis is here? Without it, I think we can limit ourselves to JS tools:
1. Create an object where lists of rooms will be stored (names can be generated unique);
2. When a client connects, we enter information in the socket about the room being connected;
3. We transfer the identifier of the connected client to the required "room" into the object with the list of rooms.
To do this, you can implement a simple module in Node.JS. You can easily implement notifications for the desired room, because. You will already have a list of all connected clients in the room. The main thing is not to forget about timeouts and automatic unsubscribing from the room.