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What is node.js auto restart

It is a set of examples and a module with common problems solved. It allows easy development and stable production.

  • Run on boot: To make your program run automaticaly on boot with Upsrart(you need to configure a .sh file and a .conf file)
  • Auto restart: autoexit module to watch all .js files if they have been changed and to restart nodejs.
  • A description of how to make your program crash proof from javascript errors. (segfaults still crash)
  • Auto reload a module: makes sense for fast development of slow loading app,

"http://github.com/shimondoodkin/node-hot-reload":http://github.com/shimondoodkin/node-hot-reload.

How to use nodejs auto restart:

Copy nodejs.sh and autoexit.js to root folder of your application for example to /var/www. Copying of autoexit.js is optional and it can be included from deps folder

Add to your script at top:

require.paths.unshift(__dirname); //make local paths accessible

And to your script at end:

// exit if any js file or template file is changed.
// it is ok because this script encapsualated in a batch while(true);
// so it runs again after it exits.
var autoexit_watch=require('autoexit').watch;
//
var on_autoexit=function (filename) { } // if it returns false it means to ignore exit this time;  
autoexit_watch(__dirname,".js", on_autoexit);
//autoexit_watch(__dirname+"/templates",".html", on_autoexit);

You might want to use: try-catch that will make your applicaiton not crash on errors

try
{
 //your code
}
catch(e)
{
 console.log(e.stack)
}

Also after serving one sucsessful request (application is fully loaded) I add an on error error handler:

if(!app_loaded)
{
 process.on('uncaughtException', function (err) {
   console.log('Caught exception: ' + err.stack);
 });
 app_loaded=true;
}

As i like it, I want it to crash on load errors and exit the application but not on application errors.

Example:

require.paths.unshift(__dirname); //make local paths accessible

var http = require('http');
var app_loaded=false;

http.createServer(function (req, res) {

  if(!app_loaded)
  {
   process.on('uncaughtException', function (err) {
   console.log('Caught exception: ' + err.stack);
   });
   app_loaded=true;
  }

  try
  {    

  res.writeHead(200, {'Content-Type': 'text/plain'});
  res.end('Hello World\n');

  }
  catch(e)
  {
   console.log(e.stack);
  }

}).listen(8124);
console.log('Server running at http://127.0.0.1:8124/');

// exit if any js file or template file is changed.
// it is ok because this script encapsualated in a batch while(true);
// so it runs again after it exits.
var autoexit_watch=require('autoexit').watch;
//
var on_autoexit=function () { console.log('bye bye'); } 
autoexit_watch(__dirname,".js", on_autoexit);
//autoexit_watch(__dirname+"/templates",".html", on_autoexit);

Edit nodejs.sh

Edit nodejs.sh to match to your server.js filename.

To launch nodejs you type

cd /var/www
./nodejs.sh

To make it work with upstart - make it run on boot

Copy nodejs.conf to /etc/init/ and modify it to point to nodejs.sh

Upstart is originated in Ubuntu linux. if your linux does not have upstart. An option for you migh be to install upstart.

To use upstart you type :

[command] + [init filename without conf extention]

start nodejs 
stop nodejs
restrt nodejs

When i start to develop I connect to the server with ssh and run:

stop nodejs
cd /var/www
./nodejs.sh

Then I will start to see application output and errors on the screen If I want to stop the server I press Control + C and the script stops. note: the output will not bet visible if logging is configured in node.sh. the output will go to log.

Nginx?

Yes I also use Nginx as front. (but it is not required). I use it to let me in the future to change and integrate different servers seemlessly. It is basicly: nginx<->nodejs as an upstream. also i have added php-cgi to nginx to use +Rock mongo+ - a mongodb db editor. also i've added a log.php , log file viewer so don't even need ssh.

Multi Process

you can put nginx or haproxy as a front and create several .conf files for the upstart.

in each you modify the execution line to contain port number ex.:

in the nodejs1.conf exec sudo -u www-data /bin/bash /var/www/nodejs-mongodb-app/nodejs.sh 8001 in the nodejs2.conf exec sudo -u www-data /bin/bash /var/www/nodejs-mongodb-app/nodejs.sh 8002

and make port as an argument to your server.js. //http.createServer(server_handler_function).listen(process.argv[2]||8001); //see http://nodejs.org/api.html#process-argv-58 //process.argv.forEach(function (val, index, array) { // console.log(index + ': ' + val); //});

To achive best performance. it was found by testing (during development of twisted and nginx) that the number of processors should much the number of cores not more not lest.

the idea behind the architecture

the idea is to add an extra level of fail-safety by using a stable system shell script to restart node instead of node itself.

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