Dane Springmeyer

@springmeyer

Basics of message passing in Node.js

NodeDC, April 25th | [get the code]

Goals

Understand tools for IPC (inter-process communication)
Build awareness of high perf designs for cpu-bound apps
Hint at advanced, emerging topics around multi-core Node

Topics

signals
udp / tcp / http
child_process: fork,send
cluster / compute-cluster

Signals

man signal (e.g. SIGHUP, SIGINT, SIGURG, etc...)
#include <signal.h>
Allow the manipulation of a process from outside its domain
Allow the process to manipulate itself or copies of itself (children)
addressed using PID (process id)

Signals

server.js

  process.on('SIGTERM', function() {
     console.log('Got a SIGTERM, exiting...');
     process.exit(1);
  });
  
  console.log('server running with PID:', process.pid);
  process.kill(process.pid,'SIGTERM');

Signals

$  node server.js 
server running with PID: 1905
Got a SIGTERM, exiting...

UDP: Internet User Datagram Protocol

man udp
#include <sys/socket.h>
simple, unreliable, connectionless
low overhead, fast
same `ip-addr:port` format as TCP/HTTP

UDP / Datagram Sockets

server.js

  var dgram = require("dgram");
  
  var server = dgram.createSocket("udp4");
  server.on("message", function (msg, rinfo) {
    console.log("server got msg: '" + msg + "'");
  });
  server.on("listening", function () {
    console.log("listening on port " + server.address().port);
  });
  server.bind(900913);

UDP / Datagram Sockets

client.js

  var dgram = require('dgram');
  
  var message = new Buffer("a datagram for you");
  var client = dgram.createSocket("udp4");
  client.send(message, 0, message.length, 900913, "localhost", function(err, bytes) {
    client.close();
  });

UDP / Datagram Sockets

$  node server.js & node client.js 
[2] 1148
listening on port 48945
server got msg: 'a datagram for you'

$  killall node

[1]-  Exit 1                  node server.js

TCP: Internet User Datagram Protocol

man tcp
builds non-blocking connection support upon sockets
reliable, flow-controlled, two-way transmission of data

TCP Sockets

server.js

  var net = require('net');
  
  var server = net.createServer(function(socket) {
    console.log('server connected with client on port ' + server.address().port);
    socket.write('server sends a tcp message for you\r\n');
    socket.pipe(socket);
  });
  server.listen(8080);

TCP Sockets

client.js

  var net = require('net');
  
  var client = net.connect(8080);
  client.on('data', function(data) {
    console.log(data.toString());
    client.end();
  });

TCP Sockets

$  node server.js & node client.js 
[1] 1764
server connected with client on port 8080
server sends a tcp message for you


$  killall node

[1]-  Exit 1                  node server.js

Child Process

Advanced means for asynchronously controlling subprocesses
Combines os.fork with tcp communication and pipes to simplify streaming message passing
Supports IPC through both signals (child.kill(signal) and bi-directional messages (child.send(message, [sendHandle]))

Child Process

child.js

  console.log('child was created with PID: ' + process.pid);
  
  process.on('exit', function(code,signal) {
      console.warn('child is exiting with code: '+ code +' and signal: '+signal)
  });
  
  process.on('message', function(data) {
      console.log('child: got message from parent: ' + data);
      process.send('hi, thanks for the message!');
  });

Child Process - Spawn

parent-spawn.js

  var spawn = require('child_process').spawn;
  
  function format(type, output) {
    console.log('child says (' + type + '): ' + output);
  }
  
  var child = spawn('node',['child.js']);
  child.stdout.on('data', format.bind(global,'stdout'));
  child.stderr.on('data', format.bind(global,'stderr'));

Child Process - Spawn

$  node parent-spawn.js 
child says (stdout): child was created with PID: 1084
child says (stderr): child is exiting with code: undefined and signal: undefined

Child Process - Fork

parent-fork.js

  var fork = require('child_process').fork;
  
  var child = fork(__dirname + '/child.js');
  
  child.on('message', function(data) {
      console.log('parent: got message from child: ' + data);
  });
  
  child.send('hello from your parent');

Child Process - Fork

$  node parent-fork.js 
child was created with PID: 1089
child: got message from parent: hello from your parent
parent: got message from child: hi, thanks for the message!

Cluster

Easily create a network of processes that all share server ports
Made possible because `child_process` module rocks

Child Process - Fork

multi-core-server.js

  var cluster = require('cluster');
  var http = require('http');

  if (cluster.isMaster) {
    for (var i = 0; i < require('os').cpus().length; i++) {
      cluster.fork();
    }
  } else {
    // Workers can share any TCP connection, in this case HTTP
    http.createServer(function(req, res) {
      res.writeHead(200);
      res.end("hello world\n");
    }).listen(8000);
  }

It gets better: Lloyd's "compute-cluster"

"Fully load" Node if you have lots of cores
github.com/lloyd/compute-cluster
github.com/lloyd/fully_loaded_node

Compute Cluster

    var cc = new ccluster({
      module: __dirname + "/bcrypt-compute.js",
      max_backlog: 100000,
      max_request_time: 2.0,
      max_processes: os.cpus().length * 2
    });
    
    var workComplete = 0;
    function doOneWorks(cb) {
      cc.enqueue({}, function(err) {
        if (!err) workComplete++;
        cb(err);
      });
    }

Dane Springmeyer

Basics of message passing in Node.js

Goals

Topics

Signals

Signals

Signals

UDP: Internet User Datagram Protocol

UDP / Datagram Sockets

UDP / Datagram Sockets

UDP / Datagram Sockets

TCP: Internet User Datagram Protocol

TCP Sockets

TCP Sockets

TCP Sockets

Child Process

Child Process

Child Process - Spawn

Child Process - Spawn

Child Process - Fork

Child Process - Fork

Cluster

Child Process - Fork

It gets better: Lloyd's "compute-cluster"

Compute Cluster

Demo! Lloyd's "Fully Loaded Node"

Demo! Lloyd's "Fully Loaded Node"

github.com/lloyd/fully_loaded_node

Thanks!