server.js

var sys = require('sys');
var connect = require('connect');
var redisFactory = require('redis-node');
var redis = redisFactory.createClient();
var server = connect.createServer();

// test with: ab -n 5000 -c 40 http://127.0.0.1:3000/folders

function buffer_to_strings(x) {
    for(var i in x) {
        if (typeof x[i] === "object" || typeof x[i] === "buffer") {
            var temp = x[i].toString('utf8');
            x[i] = temp;
        }
    }
    return x;
}

// perform asynchronous callbacks for each item in a list and then
// pass the new list off to a final callback
function map(list, each_callback, final_callback) {
    // shortcut any processing if we've got an empty list
    if (list === undefined || list === null || list.length === 0) {
        final_callback(undefined, []);
        return;
    }
    var ilist = new Array;
    var lsize = list.length;
    var mid_callback = function(err, val){
        if (err) final_callback(err, undefined);
        ilist.push(val);
        if (ilist.length == lsize) {
            final_callback(undefined, ilist);
	    }
    };
    for(var i in list) {
        each_callback(list[i], i, mid_callback);
    }
}

// work out unread count for a folder for a user
function get_folder_unread(folder, user_read, callback) {
    var c;
    redis.scard('folder:'+folder, function(e, c){
        if (e) throw(e);
        redis.sdiff('folder:'+folder, user_read, function(e,v){
            if (e) throw(e);
            callback(undefined, {folder:folder, unread:v.length, count: c});
        })
    });
}

function json_folders(req, res, auth) {
    redis.smembers('user:test:subs', function(err, subs) {
        var r = [];
        if(err) { throw(err); }
        var q = subs;
        buffer_to_strings(subs); 
        map(subs, function(f, i, c) {
                if (f != "test" && f != "mine") {
                    console.log(sys.inspect(q));
                    console.log("incorrect response from smembers:"+f);
                    process.exit(1);
                }
                get_folder_unread(f, 'user:test:read', c);
            }, function(e, newlist) {
                res.writeHead(200, {'Content-Type':'application/json'});
                res.end(JSON.stringify(newlist));
            }
        );
    });
}

function folders(app) {
    app.get('/', function(req, res, next){
        json_folders(req, res, 'test');
    });
}

server.use('/folders', connect.router(folders));

// make sure we have the right data
redis.select(2);
redis.del('folder:test');
redis.del('folder:mine');
redis.del('user:test:subs');
redis.del('user:test:read');
redis.sadd('folder:test', 1);
redis.sadd('folder:test', 2);
redis.sadd('folder:test', 4);
redis.sadd('folder:mine', 3);
redis.sadd('folder:mine', 5);
redis.sadd('user:test:subs', 'test');
redis.sadd('user:test:subs', 'mine');
redis.sadd('user:test:read', 2);

server.listen(3000);
console.log('Connect server listening');