How to reuse redis connection in socket.io?

Solution 1:

Actually you are only creating a new redis client for every connection if you are instantiating the client on the "connection" event. What I prefer to do when creating a chat system is to create three redis clients. One for publishing, subscribing, and one for storing values into redis.

for example:

var socketio = require("socket.io")
var redis = require("redis")

// redis clients
var store = redis.createClient()
var pub = redis.createClient()
var sub = redis.createClient()

// ... application paths go here

var socket = socketio.listen(app)

sub.subscribe("chat")

socket.on("connection", function(client){
  client.send("welcome!")

  client.on("message", function(text){
    store.incr("messageNextId", function(e, id){
      store.hmset("messages:" + id, { uid: client.sessionId, text: text }, function(e, r){
        pub.publish("chat", "messages:" + id)
      })
    })
  })

  client.on("disconnect", function(){
    client.broadcast(client.sessionId + " disconnected")
  })

  sub.on("message", function(pattern, key){
    store.hgetall(key, function(e, obj){
      client.send(obj.uid + ": " + obj.text)
    })
  })

})

Solution 2:

Redis is optimized for a high level of concurrent connections. There is also discussion about multiple database connections and connection pool implementation in node_redis module.

Is it possible to reuse redis connection if the cookies are same? So if someone open many browser tabs also treat as open 1 connection.

You can use for example HTML5 storage on the client side to keep actively connected only one tab and others will handle communication/messages through storage events. It's related to this question.