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Memcached in JavaScript based on Node.JS
//author: Sun, Junyi (weibo.com/treapdb)
//usage: node --nouse-idle-notification --expose-gc --max-old-space-size=8192 memcached.js
var config ={
port: 11211,
max_memory: 300 // default 100M bytes
}
var net = require('net');
var LRU = function (max) { // this LRU implementaion is based on https://github.com/chriso/lru
this.cache = {}
this.head = this.tail = null;
this.length = 0;
this.max = max || config.max_memory << 20;
setInterval(function(lru_store){
evict_count = parseInt(lru_store.length/3)
for(i=0;i<evict_count;i++){
if(process.memoryUsage().rss > lru_store.max)
lru_store.evict()
else
break;
}
console.log("element count:", lru_store.length)
},2000,this) // detection of LRU eviction every 2 seconds
};
LRU.prototype.remove = function (key) {
var element = this.cache[key];
if(element) {
delete this.cache[key];
this.length --;
if(element.prev) this.cache[element.prev].next = element.next;
if(element.next) this.cache[element.next].prev = element.prev;
if(this.head == key) {
this.head = element.next;
}
if(this.tail == key) {
this.tail = element.prev;
}
}
return element;
}
LRU.prototype.set = function (key, value) {
element = this.remove(key);
element = element || { value:value };
element.next = null;
element.prev = null;
element.value = value;
this.cache[key] = element;
if (this.head) {
this.cache[key].next = this.head;
this.cache[this.head].prev = key;
}
this.head = key;
if(!this.tail) {
this.tail = key;
}
this.length ++
if(process.memoryUsage().rss > this.max){
this.evict()
}
};
LRU.prototype.get = function (key) {
var element = this.cache[key];
if (!element) { return; }
this.set(key, element.value);
return element.value;
};
LRU.prototype.evict = function () {
if(!this.tail) { return; }
var key = this.tail;
var element = this.remove(this.tail);
};
var store = new LRU()
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': // this command is used for maintain
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.get(key)
if(obj){
response = "VALUE "+ key+" " + obj.flag+" " + obj.data.length + "\r\n"
response += obj.data + "\r\n"
response += "END\r\n"
}
else
response = "END\r\n"
break;
case 'delete':
var key = tup[1]
store.remove(key)
response = "DELETED\r\n"
break;
case 'set':
var key = tup[1]
var obj = {flag: tup[2], expire:0 , data: body}
store.set( key , obj)
response = "STORED\r\n"
break;
case 'gc': // this command is used for maintain
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') // we may got some data to handle
})
socket.on('user_event',function(){
switch(user_state){
case "reading_header": //if we are 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 we are 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
}
})
});
console.log("listening at "+ config.port)
console.log("max memory: " + config.max_memory + "M bytes")
server.listen(config.port, '0.0.0.0')
setInterval(function(){gc(); console.log(process.memoryUsage());},5000) // manually garbage collection every 5 seconds

God job!

How did you perform the tests?

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