socket.io

whys and why nots

by Robert Oroszi (oroce)

DEMO: http://nbp.ngrok.com

close adium and twitter
kill everything on *:3000: lsof -i -P | grep 3000 | awk '{print $2}' | xargs kill
run ngrok: ngrok -subdomain nbp 3000

Who am i?

@oroce

twitter github ten.izsoro@trebor

talk about yourself, noder since 2010 october
did this socket.io thing @brozie, say something about it, how it works, etc
the problems doesn't happen <10k user
most of our problems happended if there were lot of connect/disconnect and huge amount of messages (4-500kB/s)
>3 socket.io

what is socket.io

who have heard of socket.io?
who have used socket.io?
who have plans to use socket.io

what is socket.io

websocket abstraction with fallback support
client && server side library
multiple transports

why do we need websocket abstraction? because there are firewalls, antivirus sws, company proxies and mobile (3G)
ask how many heard of websocket?

http vs websocket

flickr

first of all: what is websocket? bidirectional communication between server and client
in php you have to do bizarre things like this: <?php while(true){}>

http vs websocket

flickr

first of all: what is websocket? bidirectional communication between server and client
in php you have to do bizarre things like this: <?php while(true){}>
CHECK THE DEMO SITE

we are gonna build a chat application, everybody can connect to this and can send messages

we are gonna use @gergelyke's nodeWHAT

npm install socket.io --save socket.io 0.9.X: https://github.com/LearnBoost/socket.io/tree/0.9

the original version

              
var http = require('http'),
    express = require('express'),
    fs = require('fs'),
    app = express();

app.use(express.static(__dirname + '/static'));

app.get('/', function(req, res) {
    res.send('nodeWHAT!?');
});

http.createServer(app).listen(3000, function (err) {
    if (err) return console.log(err);
});

wire socket.io

              
var http = require('http'),
    express = require('express'),
    fs = require('fs'),
    app = express(),
    sio = require('socket.io');

app.use(express.static(__dirname + '/static'));

app.get('/', function(req, res) {
    res.send('nodeWHAT!?');
});

var server = http.createServer(app);

var io = sio.listen(server);

server.listen(3000, function (err) {
    if (err) return console.log(err);
});

              
@@ -1,7 +1,8 @@
 var http = require('http'),
     express = require('express'),
     fs = require('fs'),
-    app = express();
+    app = express(),
+    sio = require('socket.io');

 app.use(express.static(__dirname + '/static'));

@@ -9,6 +10,9 @@ app.get('/', function(req, res) {
     res.send('nodeWHAT!?');
 });

-http.createServer(app).listen(3000, function (err) {
+var server = http.createServer(app);
+var io = sio.listen(server);
+
+server.listen(3000, function (err) {
     if (err) return console.log(err);
});

Run the server

npm start

Server should response to http://localhost:3000/socket.io

now let's create a client

we need a simple index.html file it'll be served by using express' built-in static middleware create a index.html file: ./static/index.html open http://localhost:3000/index.html socket.io client will be served at http://localhost:3000/socket.io/socket.io[.min].js <script src="/socket.io/socket.io.js"></script>

connect to the server

var socket = io.connect();

send some messages

socket.io works like an EventEmitter on both client and server side

Server:wiki connection*, message, disconnect

Client:wiki connect, reconnect, message, disconnect, etc

events in socket.io

Socket#send emits message event
Socket#emit( "nodejsbp" ) emits nodejsbp event

receive connections

              
io.on('connection', function (socket){
  // `socket` is a connected client
});

listen for messages

              
socket.on('message',function (data){
  // client sent something awesome for us
});

receive connection, listen for messages, broadcast them

              
io.on('connection', function (socket){
    socket.on('message', function (data){
      io.sockets.send(data);
    });
});

message handler and broadcaster for the server

             
@@ -14,6 +14,12 @@ var server = http.createServer(app);

 var io = sio.listen(server);

+io.on('connection', function (socket){
+    socket.on('message', function (data){
+      io.sockets.send(data);
+    });
+});
+
 server.listen(3000, function (err) {
     if (err) return console.log(err);
 });

client

index.html

               <!DOCTYPE html>
 <html>
   <body>
+    <h1>socket.io chat example for node.js budapest</h1>
+    <h3 id="status"></h3>
+    <ul id="messages"></ul>
+
+    <input type="text" />
+    <button>send</button>
     <script src="/socket.io/socket.io.js"></script>
     <script src="/client.js"></script>
   </body>

client.js

              
@@ -1 +1,32 @@
-var socket = io.connect();
\ No newline at end of file
+var socket = io.connect(),
+    messagesEl = document.querySelector('#messages'),
+    statusEl = document.querySelector('#status'),
+    textEl = document.querySelector('input'),
+    sendBtnEl = document.querySelector('button'),
+    me = prompt('tell me your name sunshine, you\'d be grateful');
+
+[ 'connect', 'reconnect', 'connecting', 'disconnect' ].forEach(function( evName ){
+  socket.on( evName, function(){
+    statusEl.textContent = evName;
+  });
+});
+
+socket.on('message', addMessage);
+
+sendBtnEl.addEventListener('click', function(){
+  var text = ( textEl.value||'' ).trim();
+  var date = new Date();
+  socket.send(JSON.stringify({
+    from: me,
+    text: text,
+    date: date.getHours() + ':' + date.getMinutes()
+  }));
+  textEl.value = '';
+}, false);
+
+function addMessage(data){
+  var message = JSON.parse(data);
+  var li = document.createElement('li');
+  li.innerHTML = message.from + ':' + message.text + ' (at ' + message.date + ')';
+  messagesEl.appendChild( li );
+}

</coding>

so far so good...BUT

heap

this is the v8 heap.

that amount of memory which can be allocated for our app by v8

FATAL ERROR: CALL_AND_RETRY_2 Allocation failed - process out of memory

you have to restart your application

or you can use a process manager (forever, monit, mon, supervisord) which RESTARTS for you

--max-old-space-size

GC

garbage collector

DUMMY EXPLANATION: garbage collector is responsible to automatically clean the memory, it tries to find out what parts of memory are garbage and removes them from memory

no problem, we are going to scale socket.io...

Has anybody done that?

DEMO SITE

ohhh socket.io has built-in redis store to do the scaling, which will be awesome (you hope that)

redis is a key-value store

not such string-string representation, it supports different data-structures, too

..and also it has pubsub feature

how RedisStore works

there are lot of good looking servers, i would connect to one of them

client

servers

let's connect to the first one

server1 broadcasts:

FYI: a client (name it foobar) connected to me, I stored everything in redis and this is currently know about it:

              
{
    "id": "foobar",
    "name": "awesome minion"
}

I'll let you know if something happen between us

using redis and node's built-in cluster ain't that much fun.

[...]cmd=subscribe scheduled to be closed ASAP for overcoming of output buffer limits.

ps: nodejs cluster works on the same machine

scale out w/o RedisStore

That's the fun thing :)

scaling out - problems

which proxy to use? (haproxy, nginx, http-proxy) (BalanceBattle)
sticky sessions
pubsub layer

by scaling out you'll get

lof of fucks, for sure
awesome perfomance (or not)
you can dynamically turn on/off your instances

monitor your app

npm install -g nodetime npm install -g nodefly (strongops) npm install -g node-webkit-agent

awesome, charts and etc

these are using your resources to submit the metrics

these are useful for a http application but not a realtime app

performance monitoring at its best meet DTrace and flamegraphs

flamegraph

original svg

...and don't forget the heap.

find memory leaks
monitor the number of sent and received messages (and latency and actually everything)
CLEAN UP THE BUFFER

socket.io – whys and why nots – DEMO: http://nbp.ngrok.com

oroce

socket.io – whys and why nots – DEMO: http://nbp.ngrok.com

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nodejsbp-socket.io

socket.io

whys and why nots

DEMO: http://nbp.ngrok.com

Who am i?

@oroce

what is socket.io

what is socket.io

http vs websocket

http vs websocket

we are gonna use @gergelyke's nodeWHAT

the original version

wire socket.io

Run the server

now let's create a client

connect to the server

send some messages

socket.io works like an EventEmitter on both client and server side

events in socket.io

receive connections

listen for messages

receive connection, listen for messages, broadcast them

message handler and broadcaster for the server

client

index.html

client.js

so far so good...BUT

heap

GC

garbage collector

no problem, we are going to scale socket.io...

ohhh socket.io has built-in redis store to do the scaling, which will be awesome (you hope that)

how RedisStore works

there are lot of good looking servers, i would connect to one of them

let's connect to the first one

server1 broadcasts:

using redis and node's built-in cluster ain't that much fun.

scale out w/o RedisStore

That's the fun thing :)

scaling out - problems

by scaling out you'll get

monitor your app

awesome, charts and etc

these are using your resources to submit the metrics

performance monitoring at its best meet DTrace and flamegraphs

flamegraph

...and don't forget the heap.

why not socket.io

ohh and hasn't been upgraded for 8 months

alternatives

resources

1 0