Quitting node.js gracefully


Question

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");
  response.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?

1
73
8/5/2011 3:29:01 PM

Accepted Answer

  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.

52
3/20/2014 1:14:51 PM

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.


Licensed under: CC-BY-SA with attribution
Not affiliated with: Stack Overflow
Icon