Redis publish/subscribe: see what channels are currently subscribed to

Question

I am currently interested in seeing what channels are subscribed to in a Redis pub/sub application I have. When a client connects to our server, we register them to a channel th

Answer 1

I am unaware of any specific way to query what channels are being subscribed to, and you are correct that there isn't any key created when this happens. Also, I wouldn't use the KEYS command in production anyway, as it's really a debugging command.

You have the right idea about using a set to add the user when they're online, and then query this with SISMEMBER to determine if the messages should be sent to them or added to a Redis list for processing once they do come online.

You will need to figure out when a user logs off so you can remove them from the list of online users, but I don't know enough about your system to know exactly how you would go about that.

If the connected clients have the ability to send a message back to inform the server that the message(s) were consumed, you could use this to keep track of which messages should be stored for later retrieval.

Cheers, Mike