启动方式： node --nouse-idle-notification --expose-gc --max-old-space-size=8192 memcached.js 性能：用mc_benchmark测试可以达到4万qps.

memcached.js的源码：

var net = require('net');
var store = {}

function handle_header(header,crlf_len){
    var tup = header.split(" ")
    var expect_body_len = 0
    switch(tup[0]){
        case 'get':
        case 'delete':
            expect_body_len = 0
            break
        case 'set':
            expect_body_len = parseInt(tup[4]) + crlf_len
            break
        case 'gc':
            expect_body_len = 0
            gc()
            break;
    }
    return expect_body_len
}

function handle_body(socket,header,body,call_back){
    var response=""
    var tup = header.split(" ")
    switch(tup[0]){
        case 'get':
            var key = tup[1]
            var obj = store[key]
            if(obj){
                response = "VALUE "+ obj.key+" " + obj.flag+" "  + obj.data.length + "\r\n"
                response += obj.data + "\r\n"
                response += "END\r\n"
            }
            else
                response = "NOT_FOUND\r\n"
            break;
        case 'delete':
            var key = tup[1]
            delete store[key]
            response = "DELETED\r\n"
            break;
        case 'set':
            var obj = {key: tup[1], flag: tup[2], data: body}
            store[obj.key] = obj
            response = "STORED\r\n"
            break;
        case 'gc':
            response = "OK\r\n"
            break;
        default:
            response = "ERROR\r\n"
            break;
    }
    socket.write(response,"binary",call_back)
}

var server = net.createServer(function (socket) {
    console.log("client: ",socket.remoteAddress)
    var user_state = 'reading_header'
    var buf = ""
    var header =""
    var body = ""
    var expect_body_len = 0 
    var CRLF_LEN = 2
    socket.setEncoding("binary")
    socket.on('data',function(data){
        buf += data
        socket.emit('user_event')
    })
    socket.on('user_event',function(){
        switch(user_state){
            case "reading_header":
                var pos =-1
                if((pos=buf.indexOf('\r\n'))!=-1){
                    header = buf.slice(0,pos)
                    buf = buf.slice(pos+2)
                    CRLF_LEN =2
                }
                else if((pos=buf.indexOf('\n'))!=-1){
                    header = buf.slice(0,pos)
                    buf = buf.slice(pos+1)
                    CRLF_LEN =1
                }
                if(pos!=-1){
                    user_state = 'reading_body'
                    expect_body_len = handle_header(header,CRLF_LEN)
                    socket.emit("user_event")
                }
                break
            case "reading_body":
                if(expect_body_len <= buf.length){
                    body = buf.slice(0,expect_body_len-CRLF_LEN)
                    buf = buf.slice(expect_body_len)
                    user_state = 'reading_header'
                    handle_body(socket,header,body,
                        function(){     
                            if(buf.length>0)
                                socket.emit("user_event")
                        }
                    )
                    
                }
                break
        }
    })
});
var port = 11211
console.log("listening at "+ port)
server.listen(port, '0.0.0.0')
setInterval(function(){gc(); console.log(process.memoryUsage())},5000)