Socket.io: How to count clients in a room with Socket.io-redis adapter

Question

I start building chat server using Socket.io with multiple nodes. It uses Socket.io-redis to connect all servers together and rooms for messaging.

When a client connects

Answer 1

This method works perfectly:

io.sockets.adapter.clients(["room1"], function(err, clients){
  console.log("total clients in room1: %d", clients.length);
})