Quitting node.js gracefully

I'm reading through the excellent online book http://nodebeginner.org/ and trying out the simple code

var http = require("http");

function onRequest(request, response) {
  response.writeHead(200, {"Content-Type": "text/plain"});
  response.write("Hello World");
  respons开发者_开发问答e.end();
}

http.createServer(onRequest).listen(8888); 

Now I didn't know (and I still don't know!) how to shut down node.js gracefully, so I just went ctrl+z. Now each time I try to run node server.js I get the following error messages.

node.js:134
        throw e; // process.nextTick error, or 'error' event on first tick
        ^
Error: EADDRINUSE, Address already in use
    at Server._doListen (net.js:1100:5)
    at net.js:1071:14
    at Object.lookup (dns.js:153:45)
    at Server.listen (net.js:1065:20)
    at Object.<anonymous> (/Users/Bob/server.js:7:4)
    at Module._compile (module.js:402:26)
    at Object..js (module.js:408:10)
    at Module.load (module.js:334:31)
    at Function._load (module.js:293:12)
    at Array.<anonymous> (module.js:421:10)

So, two questions:

1) How do I shut down node.js gracefully?

2) How do I repair the mess I've created?

I currently use Node's event system to respond to signals. Here's how I use the Ctrl-C (SIGINT) signal in a program:

process.on( 'SIGINT', function() {
  console.log( "\nGracefully shutting down from SIGINT (Ctrl-C)" );
  // some other closing procedures go here
  process.exit( );
})

You were getting the 'Address in Use' error because Ctrl-Z doesn't kill the program; it just suspends the process on a unix-like operating system and the node program you placed in the background was still bound to that port.

On Unix-like systems, [Control+Z] is the most common default keyboard mapping for the key sequence that suspends a process (SIGTSTP).[3] When entered by a user at their computer terminal, the currently running foreground process is sent a SIGTSTP signal, which generally causes the process to suspend its execution. The user can later continue the process execution by typing the command 'fg' (short for foreground) or by typing 'bg' (short for background) and furthermore typing the command 'disown' to separate the background process from the terminal.1

You would need to kill your processes by doing a kill <pid> or 'killall -9 node' or the like.

1. Use Ctrl+C to exit the node process gracefully

2. To clean up the mess depends on your platform, but basically you need to find the remains of the process in which node was running and kill it.

   For example, on Unix: ps -ax | grep node will give you an entry like:

   1039 ttys000    0:00.11 node index.js
   

   where index.js is the name of your node file.

   In this example, 1039 is the process id (yours will be different), so kill -9 1039 will end it, and you'll be able to bind to the port again.

As node.js is an event-driven runtime the most graceful exit is to exhaust the queue of pending events. When the event queue is empty the process will end. You can ensure the event queue is drained by doing things such as clearing any interval timers that are set and by closing down any servers with open socket connections. It gets trickier when using 3rd party modules because you are at the mercy of whether the module author has taken care to gracefully drain the pending events it created. This might not be the most practical way to exit a node.js process as you will spend a lot of effort tracking down 'leaked' pending events, but it is the most graceful I think.

Type either

process.exit()

or

.exit

to exit node gracefully.

Hitting Control + C twice will force an exit.

1) How do I shut down node.js gracefully?

Listening for a SIGINT signal. On Windows you need to listen for a ctrl-c with the readline module.

I've written my own solution to provide an application a graceful shutdown and the usage of domains: grace. It's worth to have a look.