redis works

var express = require('express')
  , redis = require('redis');

var db = redis.createClient();
var app = express();

app.use(function(req, res, next){
  var ua = req.headers['user-agent'];
  db.zadd('online', Date.now(), ua, next);
});

app.use(function(req, res, next){
  var min = 60 * 1000;
  var ago = Date.now() - min;
  db.zrevrangebyscore('online', '+inf', ago, function(err, users){
    if (err) return next(err);
    req.online = users;
    next();
  });
});

app.get('/', function(req, res){
  res.send(req.online.length + ' users online');
});

app.listen(3000);